C40 Knowledge Hub

  • Air quality - returns all articles containing BOTH air AND quality
  • Air OR quality - returns all articles containing EITHER air OR quality
  • "Air quality" - returns all articles containing the EXACT phrase
  • Air NOT quality - returns all articles containing air but NOT quality

Six impactful actions cities can take to improve their air quality

Article topics.

  • Air Quality
  • Climate Action Planning
  • Spotlight On: Climate and Clean Air

Related Knowledge

Bold action to improve air pollution can deliver swift and locally-felt rewards. These are the most impactful actions that city governments can take. We explain how to implement these measures in the related articles.

  • Adopt WHO standards as your city’s air quality target, monitor air quality and identify pollution priorities
  • Set targets to meet the World Health Organization (WHO) air quality standards (PM 2.5 levels of 10µg/m 3 ) by no later than 2030, to strengthen your mandate to act now.
  • Measure your city’s air quality to understand the problem and the impact of your actions to tackle it. Utilise emerging lower-cost sensor technologies to achieve this. Make data available to interest groups and communicate clearly to citizens, such as via weather reports and awareness campaigns.
  • Use the data collected on the main sources of air pollution in your city, including transport, buildings and the burning of dirty fuels and waste, to inform your priorities for action.
  • Enact a clean air zone to target diesel and petrol vehicle pollution
  • Make the clean air zone as large as possible, focusing on areas of highest pollution exposure.
  • Set vehicle emissions standards in the zone and charge dirty vehicles to enter, or ban them from entering, so that cars and heavy motor vehicles (including freight vehicles) become fewer and cleaner.
  • Drive a shift from personal vehicle use to public transport, walking and cycling
  • Reallocate road space to buses, cyclists and pedestrians.
  • Invest in public transport infrastructure, making it a safe, affordable and attractive choice .
  • Designate pedestrian- and cyclist -only areas, and improve cycle hire and parking facilities.
  • Align land use, planning and transport strategies. Introduce regulations for denser and affordable walking and cycling-friendly development close to transit hubs , to make essential services within walking distance, or next to, a transport station.
  • Shift vehicles to zero emission
  • Procure zero-emission buses , and other municipal vehicles.
  • Build public and municipal electric vehicle charging infrastructure , guided by benchmarks set in leading city markets, and encourage – or require – other stakeholders to invest.
  • Introduce financial incentives, such as vehicle tax exemptions, and perks like reserved electric vehicle parking spaces, to encourage public uptake .
  • Decarbonise the electricity grid
  • Commit to 100% city-wide renewable electricity by 2030  and 100% renewable energy, including electricity, heating and cooling, and transport by 2050.
  • Provide financial incentives for the installation of renewable energy on buildings . Update planning regulations to require solar on new buildings so that rooftop solar panels and other on-site power generation becomes an integral part of the city’s energy system. Lead by example by installing solar on municipal buildings .
  • Use your city’s purchasing power to procure clean energy and stimulate clean energy generation in the region.
  • Minimise the burning of solid fuels and waste
  • Improve solid waste management to reduce open burning of waste, and end large-scale waste incineration .
  • Introduce policies to limit the burning of solid fuels , such as schemes to provide access to clean, affordable alternative fuels and technologies for cooking, cleaning and lighting.

Many of these actions to achieve clean air are interlinked: charging drivers to enter a clean air zone encourages travel on public transport, bike or on foot, and raises funds for infrastructure investment, for example. A shift to electric vehicles needs to be coupled with the transition to clean energy. You can find out more about the solutions best suited to your city, and how to deliver these solutions, in our Transport , Clean Energy , Building Energy Efficiency and Waste topics.

Win-Win: Why cities should tackle climate change and air pollution together

Many of the air pollutants that harm our health also harm our climate, or share sources. This means that action to limit these emissions delivers local, near-term health benefits, as well as longer-term, global climate impacts. These are the synergies and shared solutions.

  • Air Quality Management Planning
  • Benefits of Climate Action
  • Sectoral Priorities for Air Quality
  • Strategies Toward Clean Air

Clean air, healthy planet: A framework for integrating air quality management and climate action planning

Nine steps cities can take to deliver cleaner air and better health through their climate action plan.

  • Climate Action Planning Steps and Processes

How resource-constrained cities can assess local air pollution

For cities that don’t yet have data on local air pollution, and that lack access to sophisticated monitoring equipment, emerging lower-cost sensor technologies offer a way to estimate pollution levels and exposure. This looks at how.

  • Air Quality Monitoring
  • Monitoring and Assessment of Air Quality
  • Monitoring, Evaluating and Reporting Climate Action

Pathways Air Quality (Pathways-AQ)

Linked to the Clean air, healthy planet framework for integrating air quality management and climate action planning, Pathways-AQ is a modelling tool that assesses the air quality and health implications of cities’ climate policies.

  • Cities' Air Pollution Health Impact Studies
  • Health Impacts of Air Pollution

About | Accessibility | Terms of Use | Privacy Policy | Contact | Newsletter | Careers | C40.org

© 2024 C40 Cities Climate Leadership Group, Inc. All rights reserved. | The C40 Knowledge Hub uses cookies to distinguish visitors and provide a better user experience.

  • Air & Climate
  • Drinking Water
  • Environmental Management
  • Health & Safety
  • Monitoring & Testing
  • Soil & Groundwater
  • Waste & Recycling
  • Water & Wastewater
  • Water Monitoring
  • Water Pumping
  • Air & Climate
  • Industrial Ventilation
  • Acid Gas Emissions Control
  • Activated Carbon Air Treatment
  • Activated Carbon Gas Treatment
  • Activated Carbon Treatment
  • Activated Carbon VOC Treatment
  • …and more
  • Applications
  • Atmospheric Water Generation
  • Bottled Water
  • Bottleless Water
  • Communal Water
  • Developing Countries Water
  • Domestic Drinking Water
  • Vehicles Transport
  • Acoustic Bird Control
  • Air Modeling
  • Air Quality Reporting
  • Aquatic Waste Collectors
  • Archaeology
  • Health & Safety
  • Absorbent Polymers
  • Accident Compliance
  • Accident Monitoring
  • Accident Regulations
  • Accidental Release
  • Acid Safety
  • Monitoring & Testing
  • 3D Measurement
  • 3D Scanning
  • Absorptiometers
  • Absorption Monitoring
  • Accelerometers
  • Acetonitrile Monitoring
  • Soil & Groundwater
  • 3D Groundwater
  • Acid Mine Drainage
  • Airborne Geophysical
  • Anaerobic Bioremediation
  • Aquifer Characterization
  • Aquifer Monitoring
  • Waste & Recycling
  • Acid Recycling
  • Acoustic Cleaning
  • Aerobic Biodegradation
  • Aerobic Waste
  • Aerosol Cans Disposal
  • Water & Wastewater
  • Acidic Wastewater Treatment
  • Activated Carbon Filtration
  • Activated Carbon Water Treatment
  • Activated Sludge
  • Activated Sludge Monitoring
  • Air and Water Quality Monitoring
  • Algae Bloom Monitoring
  • Aquatic Monitoring
  • Automatic Water Sampling
  • Ballast Water Monitoring
  • Axial Pumps
  • Backwashing Pumps
  • Balancing Valve
  • Booster Pumps
  • Cavity Pumps

Logo Environmental XPRT

  • … and more
  • Environmental XPRT Search
  • List your business
  • Email marketing

Ecomesure

  • How to improve air quality in a city: ...

How to improve air quality in a city: from measurement to action

Courtesy of Ecomesure

Improving ambient air quality is core to the mission of local decision makers: it is both a public health and environmental issue. The challenge is quite a tall order: outdoor air pollution causes millions of premature death worldwide, and in 2021, 91% of the world population is living in places where the World Health Organization (WHO) air quality guidelines levels are not met 1 .

Finding ways to tackle this issue seems relatively complex: pollution sources and their associated impacts are localized, but very diverse. Fortunately, local decision makers can rely on tighter regulations,   cutting-edge technological sensors which facilitate measurement ,  and inspiring best practices all around the globe.

How to tackle a global environmental and health issue and improve air quality in cities?

How to improve air quality in a city: from measurement to action

Regulation increases as scientific knowledge develops

Efforts to regulate ambient air quality are nothing new

The LRTAP 2   convention (1979) was ratified by thirty-four countries across Europe and North America. Along with its follow-up protocols, including the Gothenburg Protocol (established in 1999 and revised in 2012), this treaty is a landmark international agreement which paved the way to regulating air pollution globally and domestically. The convention put scientists and policymakers in the same room and delivered undeniable effectiveness 3 . 

The Gothenburg Protocol led the European Ambient Air Quality (AAQ) Directives (2004/107/CE, then 2008/50/CE) which set binding objectives and define specific responsibilities for European Union Member states to monitor, report on and manage air quality 4 . 

In North America, the protocol only reaffirmed existing regulation. The United States sets limits on air pollutants under the Environmental Protection Agency’s (EPA) Clean Air Act 5 , which celebrated its 50th anniversary in 2021. States are required to adopt enforceable plans to meet National Ambient Air Quality Standards (NAAQS) defined at the federal level. The need to implement air-permitting programs at the state level drives ongoing regulatory activity. The United States has also been collaborating with Canada since 1991 under the Canada-U.S. Air Quality Agreement (AQA) to address transboundary air pollution, especially acid rain and ground-level ozone 6 . 

Despite overall climate policy uncertainty, regulation is on the rise

In september 2021, the WHO drastically updated its air quality guidelines levels for main air pollutants 7 . As they serve as a reference globally, these changes should lead governments to update outdoor air quality domestic values and legal standards. 

In addition, despite mixed reactions around the COP 26 agreement among the scientific community 8 , climate commitments are on the rise 9 . Net-zero pledges and air emissions reduction targets translate into national strategies and drive an increase of regulatory binding measures. 

In North America for instance, air emission management framed the second-most common type of regulatory developments 10 . The European Union, which aims for climate neutrality by 2050, has 31 ongoing infringement procedures against 18 member states for failing to implement air quality rules domestically 11 . 

Beyond compliance: air quality best practices are flourishing in cities all over the globe

Local and targeted answers to a global and complex issue 

Urban planning decisions   made by mayors and local policy makers are a key enabler in the fight against air pollution. Outdoor air quality needs to be integrated into land use policies and documents, spanning   a wide range of topics : transportation and mobility, urban infrastructure and ecosystems (smart buildings, vegetation buffers, etc.).

Improving air quality in the city is not limited to municipalities themselves.   Decisions from the private sector   have direct influence on how the issue is being addressed locally, either driven by regulatory pressure or voluntary. From global coalitions such as the recently announced Alliance for Clean Air 12   to individual businesses integrating air quality to their management scope (through ESG / sustainability program or ISO type certification for instance), initiatives are spreading.

Activities from citizens matter , too. In Massachusetts for instance, activists are pushing for a new legislation to renew air quality monitors in order to better understand and combat pollution at the local level 13 .

"Urban Pedestrian Zone": how cities are acting locally to reduce air pollution from transportation?

Urban traffic is one of the main sources of ambient air pollution. The rise of   urban pedestrian zones   or   zero-emission areas   in European cities is a good example of how local action can be efficient. 

Driven by compliance, local authorities - and mayors in particular, are   leveraging regulatory requirements as a toolbox   to progressively tax or ban the most polluting vehicles, along with making cleaner transportation options safer, cheaper and easily accessible for residents (developing walk and bike lanes, prioritizing electric vehicles, making public transportation free or cheaper, etc.). These incentives help limit the concentration of air pollutants downtown, such as NO 2 ,PM 10 /PM 2.5 .

Urban pedestrian zones started in Sweden in 1996 and are now spanning over   230 cities in Europe   including London, Amsterdam, Barcelona and Paris. They are also emerging out of the old continent. Seattle, for instance, announced the implementation of its first zero-emission area in summer 2022 14 .

Monitoring outdoor air quality to support decision making

Air pollution comes from a mix of different sources. Its impacts are hyper-local, they vary over the course of a day and from one city block to the other.

Understanding air pollution requires both to identify the different   sources of pollutants   in ambient air, as well as their   concentration levels . This dual analysis helps understand   how communities are being exposed in each urban area   and pinpoint   pollution hotspots.

Understanding the baseline situation by   mapping urban air pollution   is essential for local decision makers to understand pollution-related challenges and lead evidence-based urban planning. 

Until recently, the extent and quality of analysis have not always been granted. Conventional reference stations deployed in cities are big in size, complex to manage and costly, limiting their density and to the same extent the precision of local diagnostics. 

New generation   connected air quality monitors ,   fixed or mobile , are a game-changer. Solutions developed by Ecomesure deliver accurate hyper-local air quality data, as the sensors they integrate follow a controlled calibration process, automated and strengthened by the application of artificial intelligence models. These compact monitors are complementary to existing instruments and often supplement them, enabling   greater density of outdoor air quality data   and real-time insight on pollution patterns within the city. 

Air quality data can be combined with other sources, such as peak road traffic and types of circulating vehicules,to provide municipalities with a better understanding of air pollution challenges and support their decision making process with stronger insight. This is what the local council community of Versailles Grand Parc is doing in France.

Leveraging existing city infrastructure to capture information and turn it into action

How to improve air quality in a city: from measurement to action

These solutions offer a major benefit: they can be installed in pretty much any existing city infrastructure. Some municipalities are leveraging their city-owned fleet vehicles (police cars, fire engines, public buses) to capture hyper-local air quality information with  mobile sensors mounted on vehicles , while driving up and down the city.  

Technilum, a designer and manufacturer of urban lighting products for 50 years, has developed  a full-featured street light enhanced with an Ecomesure air quality monitor . Connected to the light’s RGB LED lamp, the system  visually informs passers-by  of the surrounding air pollution by adjusting the lighting color to changes in air quality.

Generated insights are leveraged to  drive meaningful strategies at the local level  and to  analyze the impact of clean air initiatives . In France, the local council community of Versailles Grand Parc is developing visual analytics for municipalities in charge of transportation. Local decision makers are able to suggest, for instance, alternative itineraries based on congestion and air pollution levels. 

Outdoor air quality data are also leveraged to  engage and empower citizens . Pittsburg, which consistently ranks among the most polluted American cities, shares interactive  online tools on air quality : pollutant levels across the city, how they spread out, how the city’s air quality compares with other cities, etc. The goal is to provide citizens with transparent information in order to  better understand air quality ,  spread the word  and  raise their voice  to be heard by local representatives.

Are you looking to improve outdoor air quality monitoring in your city? To learn how Ecomesure can help you,  reach out to our experts .

Most popular related searches

  • ambient air quality
  • air quality data
  • air quality monitor
  • national ambient air quality standard
  • urban air quality
  • urban air pollution
  • ambient air quality monitoring
  • ambient air quality monitor
  • air pollution
  • ambient air quality standard
  • Placeholder

Customer comments

No comments were found for How to improve air quality in a city: from measurement to action . Be the first to comment!

Great! comment successfully added!

The captcha is not valid

Doubleclick image

Advertisement

Advertisement

Using green infrastructure to improve urban air quality (GI4AQ)

  • Perspective
  • Open access
  • Published: 16 March 2019
  • Volume 49 , pages 62–73, ( 2020 )

Cite this article

You have full access to this open access article

  • C. Nick Hewitt   ORCID: orcid.org/0000-0001-7973-2666 1 ,
  • Kirsti Ashworth 1 &
  • A. Rob MacKenzie 2  

28k Accesses

135 Citations

20 Altmetric

Explore all metrics

As evidence for the devastating impacts of air pollution on human health continues to increase, improving urban air quality has become one of the most pressing tasks facing policy makers world-wide. Increasingly, and very often on the basis of conflicting and/or weak evidence, the introduction of green infrastructure (GI) is seen as a win–win solution to urban air pollution, reducing ground-level concentrations without imposing restrictions on traffic and other polluting activities. The impact of GI on air quality is highly context dependent, with models suggesting that GI can improve urban air quality in some situations, but be ineffective or even detrimental in others. Here we set out a novel conceptual framework explaining how and where GI can improve air quality, and offer six specific policy interventions, underpinned by research, that will always allow GI to improve air quality. We call GI with unambiguous benefits for air quality GI4AQ. However, GI4AQ will always be a third-order option for mitigating air pollution, after reducing emissions and extending the distance between sources and receptors.

Similar content being viewed by others

how to improve air quality in city

Strategies to achieve a carbon neutral society: a review

Lin Chen, Goodluck Msigwa, … Pow-Seng Yap

how to improve air quality in city

The costs and benefits of environmental sustainability

Paul Ekins & Dimitri Zenghelis

how to improve air quality in city

A quantitative assessment of natural and anthropogenic effects on the occurrence of high air pollution loading in Dhaka and neighboring cities and health consequences

Riaz Hossain Khan, Zahidul Quayyum & Shahanaj Rahman

Avoid common mistakes on your manuscript.

Introduction: Urban air quality and green infrastructure

More than half of the world’s population currently live in urban areas, most of which have outdoor air quality that fails to meet World Health Organisation guidelines for healthy living. Air pollution, principally caused by nitrogen dioxide (NO 2 ) and fine particles of aerodynamic diameter less that 2.5 µm (PM 2.5 ), is now the leading environmental cause of mortality world-wide, causing ~ 3 million premature deaths a year, twice the number due to road traffic accidents (World Health Organisation 2016 ). While reducing pollutant emissions is always the most direct way to improve urban air quality, authorities world-wide have, with few exceptions, struggled to provide adequate air quality improvements through emission control strategies alone. Policy makers are increasingly turning to complementary methods of reducing human exposure to air pollutants as cities expand, the number of motor vehicles grows (globally from < 0.1 × 10 9 in 1960 to > 1 × 10 9 in 2017), and distances driven increase. The relative growth in diesel vehicle numbers, many of which are not compliant with emission regulations (Schiermeier 2015 ), is an important additional adverse factor in some countries, including the UK.

One increasingly promoted method for air pollution mitigation is the use of green infrastructure (GI): street and park trees, green walls, green roofs (Berardi et al. 2013 ), and other means of introducing vegetation into the urban landscape (Beatley 2016 ), on the basis that pollutants deposit more efficiently onto vegetation than onto smoother, impervious, artificial surfaces (Fowler et al. 2009 ; Nowak et al. 2013 ; Neft et al. 2016 ). However, the empirical evidence for the effectiveness of GI for air quality is weak. Without a method to systematically assess GI impacts on urban air, it will remain difficult for researchers and practitioners to determine how and where GI can improve air quality. In offering such a method here, we recognise that known modelling deficiencies and lack of ground-truthing field observations limit the precise quantitative assessment of specific GI interventions. Whereas previous reviews of this topic have focussed on one aspect of the problem (e.g. removal of particles; Janhäll 2015 ) or have been rather unselective (e.g. Abhijith et al. 2017 ), here we critically appraise the evidence for the effectiveness of GI in a conceptual framework and offer six specific policy interventions that can only benefit air quality.

GI is part of the urban canopy, set within, and contributing to, its heterogeneity. The character of the urban canyon adds complexity but also offers opportunities to identify sites where GI will have unambiguous benefits for air quality (which we call GI4AQ). Below, we use ‘canopy’ to refer to the volume-filling effects of buildings and trees; we use ‘crown’ when discussing individual tree tops. Metrics describing stem or stand densities do not adequately define the urban tree canopy because of differing tree management methods (e.g. pollarding). Planar cover, while an undoubtedly useful measure (e.g. as used in the i - Tree Canopy model), leaves the vitally important vertical dimension unconstrained, and neither stem count nor tree-crown cover situates GI three-dimensionally in the urban canyon. Here, we use three underpinning urban canopy-related axioms: that GI will affect air quality most significantly when it (i) fills canopy gaps and edges to alter flow (Oke 1988 ; Ng and Chau 2012 ), (ii) alters mean aerodynamic roughness (Barnes et al. 2014 ; Jeanjean et al. 2015 ) or (iii) increases the absorbency of surfaces adjacent to polluted air held within the urban canopy (Pugh et al. 2012 ).

Ground-level concentrations of urban air pollutants are a complex function of emissions, dispersion (stirring and mixing), deposition and chemistry. Much of this complexity is due to the spatial pattern of the urban canopy (Ratti et al. 2006 ; Abhijith et al. 2017 ), within which people are exposed to polluted air. The urban canopy occupies near-surface volume (Henderson et al. 2016 ), interacting with the air flow (Oke 1988 ). Stirring of parcels of air stretches and folds them, producing irregular blobs and filaments of relatively undiluted emissions interleaved with cleaner air, and mixing dilutes emissions by intermingling them with cleaner air at the molecular scale (Prather and Jaffe 1990 ; Tan et al. 1998 ). For urban land-classes dominated by transport corridors (Owen et al. 2006 ), the landscape is more open with fewer buildings and the canopy largely comprises vegetation (Choi et al. 2014 ; Abhijith et al. 2017 ).

Despite the complexities of how urban form impacts the atmospheric concentrations of pollutants, developing a framework around the urban-canopy axioms above can guide policy makers on how and where GI can be used to improve air quality—GI4AQ—and where GI is unhelpful or even detrimental to air quality. Inserting or removing GI with the intention of improving air quality must be considered in the context of other possible co-benefits and costs. For example, urban trees provide habitats that enhance biodiversity, provide shade and other micro-climate services (Livesley et al. 2016 ; Salmond et al. 2016 ) and, to a minor extent, sequester carbon dioxide from the atmosphere (Nowak and Crane 2002 ). Like all urban infrastructure, GI systems, from sophisticated vertical forests (Moeller 2015 ) to shrubs in planters, require proper installation and regular long-term maintenance to prevent damage to buildings, roads and pavements (Trees, Design and Action Group, TDAG 2012 , 2014 ). Planning with GI should include scenario-based ‘futures thinking’ to ensure long-term efficacy (Lombardi et al. 2012 ; Hale et al. 2015 ). For example, trees in street canyons which currently reduce dispersion of traffic pollutants (see below) may be less of a concern in the future when electric or hydrogen vehicles will cause much less street-level pollution emissions (Jacobson et al. 2005 ). Likewise, in the past, when major pollution sources were mainly situated above roof level, the impact of street trees on pollutant dispersion within the street canyon was not a significant concern.

A useful conceptualisation of air pollution mitigation in urban areas is “Reduce–Extend–Protect”. Reducing emissions is always the most effective method of reducing human exposure to pollutants and should always be the primary focus of mitigation action. GI does not play any explicit role in this. Extending the distance between sources and receptors, enhancing dilution and dispersion and hence reducing concentrations at a given receptor, is usually the second-best method of reducing exposure. This may be done by physically extending the distance between, for example, road vehicles and pedestrians, or by placing barriers to flow between sources and receptors. GI can act in this role, for example when hedges are used to separate traffic and pedestrians, virtually extending the distance between source and receptor. Protecting receptors involves introducing direct interventions that reduce concentrations at the receptor site, and here GI can be used in several configurations, as discussed below. This will normally be the third-best mitigation option.

Dispersion of air pollutants

Trees and hedges provide semi-permeable obstacles to the flow of air (Bradley and Mulhearn 1983 ; Raine and Stevenson 1977 ; Tiwary et al. 2005 ; Gromke et al. 2016 ; Tong et al. 2016 ), deflecting stream-lines, introducing turbulence and increasing dilution and hence virtually extending the distance between source and receptor. Several structural factors, such as plant height and morphology, affect the way vegetation interacts with flow, and can be considered design parameters (Baldauf 2017 ) for GI4AQ. Dense vegetation acts almost as a bluff body, with negligible permeating flow and a region of recirculation behind the vegetation (Tiwary et al. 2005 ). For crown porosities above ~ 50%, no recirculating region forms behind the obstacle (Baltaxe 1967 ; Bradley and Mulhearn 1983 ). Porosities of common urban GI4AQ are listed in a recent review (Abhijith et al. 2017 ).

Regions of accelerating and decelerating air stir pollutants into filamentary patches of higher and lower concentrations (Gromke and Blocken 2015 ) (Fig.  1 ). Resolving these spatial variations at the street scale requires resource-intensive computational fluid dynamics (CFD) modelling, supported by site-specific crown and canopy measurements (Hofman et al. 2016 ). The modelled aerodynamic effect of street trees for two main roads in London, for example, was quasi-two dimensional, and reductions in the average concentrations in the street canyons were negligible (1%) (Jeanjean et al. 2017a , b ). Under other circumstances, canopy-induced turbulence in the model led to three-dimensional stirring and mixing, reducing average ground-level concentrations (Barnes et al. 2014 ). Modelling using a remotely sensed inventory of tree-top pattern calculated a median reduction of 8% in ground-level concentrations of PM 2.5 across a specific city centre due to the dispersive effect of the trees present (Jeanjean et al. 2015 ). In contrast, a recent summary reported increases of between 0 and 96% in modelled average street canyon pollutant concentrations due to the introduction of trees (Abhijith et al. 2017 ), highlighting both the uncertainties in current models and the need for caution when introducing trees to street canyons.

figure 1

Schematic representation of flow around a dense tree crown, a in elevation and b in plan, and c street trees can cause areas of relatively lower (blue) and higher (red) ground-level pollutant concentrations, with the street-average concentration shown in yellow (adapted from Jeanjean et al. 2017 ). In the plan view cartoon of a street canyon containing trees ( c ), the trees will be approximately located at the intersections of the red and blue filaments of air with higher and lower pollutant concentrations, initiating disturbances in the down-wind flow at these points

Contiguous and dense tree crowns can effectively separate the air below the canopy from that above (Gromke and Blocken 2015 ). A reversal of flow at 2 m above street level for street trees spaced at 25-m intervals (Moradpour et al. 2017 ) dramatically exemplifies such behaviour in models. In parks, traffic-free plazas, and other pedestrian areas without significant ground-level anthropogenic pollution sources, but with dense vegetation canopies, the below-canopy air will always be cleaner than that above the canopy due to enhanced deposition of pollution onto the vegetation as the air percolates through the canopy (see below). However, when canopy closure occurs in a street canyon containing ground-level sources of pollution, pollutants may be trapped, leading to increased ground-level concentrations (Vos et al. 2013 ; Abhijith et al. 2017 ). In such situations, local emission controls should be implemented to reduce or remove the ground-level pollution source. When emissions cannot be adequately reduced, it is necessary to identify which elements of the urban canopy are inhibiting vertical mixing and, hence, what modifications to the canopy (including tree crowns) can be made to improve ventilation and so improve ground-level air quality (GI4AQ Policy Intervention 1, see Table  1 ). CFD studies provide the only quantitative method currently available to quantify ventilation, but many such studies do not capture the intermittency of turbulent flow and all lack field observations for model evaluation.

Dispersion will always ultimately transfer pollutants down concentration gradients into the cleaner atmosphere or towards absorptive surfaces. As pollutants move from their source, turbulence dilutes the plume by mixing in cleaner air, as recognised in operational air quality models (e.g. Heist et al. 2013 ; Stocker et al. 2013 ; Design Manual for Roads and Bridges 2017 ) and more sophisticated simulations (Tong et al. 2016 ). The introduction of linear obstacles (e.g. hedges or fences) between source and receptor zones displaces the pollutant plume upwards (Bowker et al. 2007 ), extending the effective path-length of air from source to receptor, and may also promote dilution by enhancing turbulence. Hence hedges and fences can reduce concentrations along pavements, side-walks and other pedestrian areas adjacent to traffic (Gallagher et al. 2015 ; Gromke et al. 2016 ; Abhijith et al. 2017 ) (Fig.  2 ). Decreases in pollution concentrations of 20–70% (average 52%) behind a 1-m-high impermeable barrier in an open setting have been modelled (King et al. 2009 ). The effect of barriers on concentrations is complicated by street-scale circulations within a street canyon (McNabola et al. 2009 ; Gromke et al. 2016 ; Abhijith et al. 2017 ).

figure 2

Effect of a permeable linear barrier or hedge on pollutant concentrations. The pollutant concentration experienced by the child receptor is the mass-weighted average of the concentrations through ( c 1 ) and over ( c 2 ) the linear barrier. Along paths d 1 and d 2 , pollutant concentrations are diluted by mixing and deposition. Deposition dominates for d 1 , mixing dominates for d 2 , with c 2 decreasing approximately exponentially (see inset). The characteristic mixing length-scale is determined by local turbulence. In the absence of the linear barrier, the receptor experiences higher concentration, c 0 , diluted over shorter distance, d 0 , and not subject to enhanced deposition to vegetation

As the porosity of the barrier increases, the effective path-length decreases (Fig.  2 ) but the opportunity for removal of particles by deposition increases (Tong et al. 2016 ). The collection efficiency for a 2.2-m-high, 1.6-m-wide porous hawthorn hedge was measured at ~ 1% for particles < 2.5 µm diameter, increasing to ~ 30% for particles of 15 µm diameter. These results could be reproduced adequately using 2D modelling with appropriate treatment of drag and particle collection (Tiwary et al. 2005 ; Guo and Maghirang 2012 ). In general, linear barriers are helpful in aiding dispersion and deposition and hedges (and fences) may therefore offer some protection to pedestrians (GI4AQ Policy Intervention 2). Such obstacles need not be GI (Gallagher et al. 2015 ), although porous GI or a mix of hard barrier and GI (Tong et al. 2016 ) would offer co-benefits through enhanced deposition of both large (diameter, d  > 1 µm) and small ( d  < 100 nm) particles (Neft et al. 2016 ).

Deposition of air pollutants

In contrast to dispersion, the deposition of a pollutant to a surface results in permanent loss from the atmosphere, and hence a reduction in total atmospheric loading. Wet deposition is associated with precipitation and proceeds at the same rate to all surfaces (Sehmel 1980 ; Fowler et al. 2004 ). However, the rate of dry deposition is highly dependent on the macroscopic characteristics of the surface, i.e. available surface area (Padro 1996 ; Fowler et al. 2004 ; Gröte et al. 2016 ) and surface aerodynamic roughness (Sehmel 1980 ), and GI can potentially protect against air pollution by enhancing the deposition rates of pollutants and hence reduce concentrations of pollutants in the vicinity of receptors. The mix of plant species and size used in GI, and their spatial relationship to the built environment, will determine these deposition parameters and, hence, determine the maximum potential rate of pollutant dry deposition. Particle deposition velocities as high as 11 mm s −1 have been measured to urban trees, compared with around 3 mm s −1 to adjacent grass, and dry deposition has been estimated to account for ~ 70% of total deposition to urban trees compared with ~ 25% to grass (Fowler et al. 2004 ).

Vegetation with higher surface area, greater rates of transpiration, and longer in-leaf periods result in the greatest enhancements in dry deposition over that to bare surfaces (Padro 1996 ; Branford et al. 2004 ; Nowak et al. 2006 ; Cabaraban et al. 2013 ; Gröte et al. 2016 ). For this reason, the selection of species is critical in determining the increased pollutant removal achieved through the addition of GI to the built environment. For example, the available surface area of deciduous broad-leaved trees can reach up to 6 m 2 per m 2 of bare ground (Nowak et al. 2006 ), 20% more than evergreen needle-leaf trees (van den Hurk et al. 2003 ). Leaf and plant morphology also contribute to the overall rate of dry deposition to different vegetation species and should be considered in combination with surface area (Gröte et al. 2016 ).

On-line tools have been developed to assist in species selection (e.g. i-Trees Species Selector 2017 and the derivative European Specifind 2017 ) but these are of necessity black-box database search instruments giving a list of potential species that acts as a starting point for refinement against other considerations. These on-line tools usually assume optimal physiological behaviour of the GI, but poor soils, high temperatures exacerbated by the urban heat island effect and limited water availability often combine to reduce leaf area and transpiration, reducing deposition rates to well below that for unstressed vegetation (Calfapietra et al. 2015 ). Effective management of GI (Lu et al. 2010 ; Young 2011 ; Pincetl et al. 2013 ), e.g. to avoid water stress, is therefore essential to ensure its long-term health and functioning and to maximise deposition rates (GI4AQ Policy Intervention 3).

In addition to plant morphology, the characteristics of the canopy play an important role in modifying surface roughness and turbulence. There is the potential to design heterogeneity into the urban canopy to exploit edge effects and maximise deposition. Particle removal by dense forest canopies has been observed to be over 30% higher than to adjacent open heathland with the greatest increases (over 50%) occurring at the forest edge (Branford et al. 2004 ).

As the rate of dry deposition is proportional to the local concentration of the pollutant (for a given surface and wind flow), GI is most effective at improving air quality in locations where pollutant concentrations are highest (Nowak et al. 2006 ; Morani et al. 2011 ; Cabaraban et al. 2013 ) and where residence times are longest (Pugh et al. 2012 ). Where GI acts on large volumes of air, for example in the case of green roofs upwind of street canyons, where there will not be a shallow boundary layer or constrained volume of air above the roof surface, the potential to reduce atmospheric concentrations of pollutants is very limited (typically < 1%) (Donovan et al. 2005 ; Pugh et al. 2012 ). The capital and maintenance cost of green roofs is therefore likely to be a very poor investment for air quality mitigation.

Measuring or modelling the potential mass of pollution deposited for given air concentrations can make the GI4AQ effect appear to be significant (Nowak et al. 2006 ; Speak et al. 2012 ; Berardi et al. 2013 ), but calculations or measurements of deposition should be combined with modelling of resultant changes in atmospheric concentrations to properly estimate the actual air quality benefits of GI4AQ (Hofman et al. 2016 ). Recent developments in the application of eddy covariance methods for measuring deposition rates of pollutants offer the possibility of model validation, although probably at only a relatively large (urban park) scale (Guidolotti et al. 2017 ). In fact, increasing deposition rates will often not result in discernible reductions in atmospheric concentrations, but where GI acts on relatively small volumes of air and ventilation rates are relatively low, models predict that the effects on ground-level air quality can be very large (Pugh et al. 2012 ). For this reason, the introduction of large areas of green walls in street canyons may be particularly effective at improving ground-level air quality (GI4AQ Policy Intervention 4).

Creating “green oases”, i.e. slowly ventilated areas containing or surrounded by GI but with no internal anthropogenic pollutant sources, will always lead to an improvement in air quality. Green oases can vary in scale from a bench or other small areas surrounded by relatively tall GI, e.g. hedges, up to pedestrianised and verdant street canyons, plazas or courtyards, or even to a park covered in an extensive vegetated trellis roof. In these cases, the amount of GI present should be maximised (GI4AQ Policy Intervention 5).

Negative impacts of trees on air quality through effects on atmospheric chemistry

All plants synthesise reactive volatile organic compounds (biogenic VOCs) and emit them to the atmosphere. The single most important bVOC by emitted mass and reactivity is isoprene (C 5 H 8 , 2-methyl-1,3-butadiene) but several tens of other bVOCs have significant effects in the atmosphere (Atkinson and Arey 2003 ; Guenther et al. 2012 ). As well as these constitutive emissions, biotic and abiotic stresses may induce the production of many other compounds (Hatanaka 1993 ). For an overview of bVOC synthesis pathways, their biological functions and their emissions and effects in the atmosphere, see Laothawornkitkul et al. ( 2009 ).

Although the vast majority of VOCs emitted globally are biogenic in origin (Guenther et al. 1995 , 2012 ), emissions from anthropogenic sources are relatively much more important in urban areas. Nevertheless, isoprene, which has both biogenic and anthropogenic sources, may still be important in urban areas, especially in summer (e.g. Wang et al. 2013 ), even in temperate cities such as London (Langford et al. 2010 ).

In the context of urban GI, the most significant bVOC emissions are those from trees, since in almost all urban situations trees will contribute the majority of leaf biomass. Constitutive emissions vary considerably in chemical composition between tree species. Urban areas may contain a large number of tree species, as native species will often be augmented by a wide range of exotics, especially in parks and gardens, all with differing bVOC emission profiles and rates. For example, 126 different species of mature trees have been recorded in London (Treeconomics 2015 ) and 170 in Beijing (Yang et al. 2005 ).

bVOCs take part in chemical reactions in the atmosphere that can lead to the formation of ozone (MacKenzie et al. 1991 ; Chameides et al. 1988 ; Atkinson and Arey 2003 ; Donovan et al. 2005 ; Calfapietra et al. 2013 ) and organic aerosol particles (Carlton et al. 2009 ; Hallquist et al. 2009 ; Mentel et al. 2009 ; Wyche et al. 2014 ), both of which are important secondary air pollutants. Since it takes several hours before these chemical reactions generate high pollutant concentrations of ozone or particles, the precise location of bVOC-emitting GI within the urban canopy is not important. This is in contrast to the dispersion and deposition effects of GI, which are highly location-specific. From a policy perspective then, when GI is being implemented for pollution control by dispersion and deposition, the negative effects on secondary air pollution (i.e. ozone and particle formation) can be considered separately, at the urban air-shed, rather than the local, scale.

bVOC emissions from a typical urban tree population contribute on the order of 10% to ozone concentrations within and downwind of large city-regions (MacKenzie et al. 1991 ; Chameides et al. 1988 ; Donovan et al. 2005 ; Calfapietra et al. 2013 ). Unfortunately, there is no easy way to reliably predict whether or not a given tree species emits a particular bVOC, or at what specific rate. Notwithstanding this, if the total urban tree population is to be altered significantly, e.g. by more than ~ 10%, care should be given to the choice of tree species used, in order to not exacerbate the bVOC emission rates at the urban air-shed scale (GI4AQ Policy Intervention 6). Several (incomplete and largely uncritical) bVOC emission databases ( http://www.es.lancs.ac.uk/cnhgroup/iso-emissions.pdf ; Keenan et al. 2009 ; http://bai.acom.ucar.edu/Data/BVOC ) may be referred to when selecting tree species for planting, based on their likely bVOC emissions. A more sophisticated assessment might weigh deposition benefits against secondary pollutant formation potentials for individual tree species, to generate, for example, an “Urban Tree Air Quality Score” (Donovan et al. 2005 ).

Two policy-relevant implications arise from the fact that trees take decades to mature, with bVOC emissions increasing as their leaf area increases over time. First, in the next few decades there is the possibility that urban transport will become less polluting than currently, leading to lower secondary pollutant formation. Ozone isopleths, or ‘Sillman plots’ ( 1999 ), which relate ozone pollution to NO x and VOC emissions, can be used to estimate the emission reductions from traffic needed to ensure that any additional bVOC emissions resulting from tree planting do not produce additional ozone. Secondly, climate change will lead to increased temperatures, especially in urban areas (Fowler et al. 2008 ; Estrada et al. 2017 ), increasing bVOC emissions and therefore exacerbating ozone pollution events (Yang et al. 2008 ), enhancing the relevance of Policy Intervention 6.

Policy guidance and conclusions

Numerous modelling studies suggest it is possible to make GI interventions that will improve urban air quality, but there is little unequivocal empirical evidence or validation to support this, although this may change as new measurement technologies become available (e.g. Guidolotti et al. 2017 ). In situations where pollutant concentrations change rapidly in space and time (e.g. near to roads), measuring small changes in concentrations and attributing these to the introduction of GI is almost impossible. Laboratory-scale experiments have limited utility because deposition and dispersion are very tightly coupled to the three-dimensional urban form and the synoptic-scale flow, while designing field-scale experiments involving GI with adequate controls is difficult, if not impossible. Policy makers must therefore make decisions on GI largely based on model predictions rather than empirical evidence. To aid this, we have identified six GI4AQ Policy Interventions, deduced from an understanding of the processes operating in the near-surface urban air volume (Table  1 ). All these interventions are risk-free in the sense they can only benefit ground-level air quality, although the effectiveness of specific interventions will vary from the insignificant to the highly significant. Effectiveness may be hard to determine empirically. This is in contrast to other possible actions involving GI that may be detrimental to air quality (e.g. introducing trees into a street canyon, which may increase canopy closure and reduce ventilation rates), or those that may have no discernible effects on air quality (e.g. building green roofs).

A common fallacy concerning urban GI is that increasing the amount of vegetation reduces ground-level pollutant concentrations linearly (i.e. that doubling leaf area will half pollutant concentrations). The vegetation deposition sink is at a distance from the pollutant emission source, so atmospheric concentrations will be always a non-zero, positive-definite, balance of emissions, advection, deposition, and reaction. Not accounting for other terms in the budget leads to over-estimation of the efficacy of green roofs and other forms of GI on air quality, to the detriment of rational decision making.

Figure  3 is a flow chart designed to help policy makers navigate the few critical decisions that determine the suitability of GI4AQ—from a scientific perspective—at all relevant spatial scales, from the smallest urban park to a ‘million trees’ Initiative. The flow chart indicates that some policy decisions (marked by green paths in the figure) may be safely reached by the application of simple rules of thumb and the existing literature. Other decisions require specialist and resource-intensive model simulations of dispersion and/or atmospheric chemistry (red paths in the figure) but may still warrant investigation. GI choices shown in grey will be ineffective for air quality improvement but may, of course, still provide other ecosystem services (Beatley 2016 ). The flowchart should therefore help to prioritise GI interventions when intended for AQ benefits and indicate which GI investment decisions should be supported by more detailed studies.

figure 3

Flow chart to aid GI4AQ decision making. PI1, PI4, PI5 and PI6 refer to the GI4AQ Policy Interventions shown in Table  1 . “Regional tree population” refers to the tree population in an area relevant to the production of ground-level ozone from bVOC precursors, i.e. equivalent to several hours travel time of a typical air parcel. “Δozone” is the expected increment to peak ground-level ozone within or downwind of the urban area due to the change in regional tree population. Grey boxes indicate that GI is not suitable for air quality improvements but may provide other ecosystem services. Red boxes require further site-specific measurements and/or modelling before a rational decision can be reached. Capturing evidence used along the paths to a Green box (‘Go’) will improve decision-making transparency and resilience (e.g. Lombardi et al. 2012 ; Hale et al. 2015 ). Refer to main text for methods to assess the impact on ozone and for a definition of ‘green oasis’. Appropriate spatial scales for GI4AQ are mapped in Fig.  4

GI4AQ can be effective over a range of horizontal and vertical spatial scales, although there are limitations. It may be helpful to consider an intervention in terms of its characteristic horizontal scale and its height-to-width aspect ratio (Fig.  4 ). When horizontal length scales and aspect ratios are small, residence times are short and there is little opportunity for deposition to become effective. When aspect ratios are large, especially at large horizontal scales, it becomes physically impossible to manufacture the GI4AQ intervention. GI4AQ is effective where deposition can be enhanced by holding air for longer near vegetation. The space domains in which GI4AQ is likely to be effective range in size from a small “green oasis” such as a bench closely surrounded by high hedges to a dense urban woodland.

figure 4

Plot of log(aspect ratio) against log(linear dimension in m), showing space domains in which GI4AQ is feasible and potentially effective. Examples of specific GI4AQ typologies are (from left to right), a bench closely surrounded by high hedges; an extensive green wall in a street canyon, where W is the width of the street; a tunnel or canopy of dense vegetation offering protection to pedestrians; a city park with a dense tree canopy. The domain space in the top-right of the figure is physically inaccessible because of limits to the heights of trees and other forms of GI. Green roofs have horizontal scales of tens of metres and H / W  ≪ 1, and so fall in the bottom left corner of the figure, where GI is ineffective for AQ mitigation (see text)

Green roofs have horizontal scales up to tens of metres and aspect ratios ≪ 1, and so fall in the bottom left-hand corner of Fig.  4 . While they enhance the deposition of pollutants from the atmosphere by increasing the available surface area (Yang et al. 2008 ; Treeconomics 2015 ), they are unlikely to make an appreciable difference to ground-level pollutant concentrations since they act on the very large volume of air above the urban canopy (Pugh et al. 2012 ). Vertical forests (e.g. Moeller 2015 ) have modest horizontal extent and very large aspect ratios but will be ineffective as GI4AQ because they do not produce either a closed canopy or an open top green oasis. In contrast, green walls in street canyons with aspect ratios greater than about unity [log ( H / W ) > 0] may make appreciable differences to ground-level concentrations (Pugh et al. 2012 ).

Despite the complexities of modern cities, the conceptual framework outlined above, underpinned by research, allows us to provide guidance to policy makers on where and how GI can benefit urban air quality. When proper consideration of context is made, there are clear and substantive opportunities to employ GI to improve air quality. The framework will also help practitioners and policy makers assess new research on GI and air quality as it becomes available. Properly designed and implemented GI4AQ (Lombardi et al. 2012 ; Trees, Design and Action Group 2014 ; Beatley 2016 ) may help cities meet several of the UN’s Sustainable Development Goals, but poorly designed GI may be ineffective or even detrimental to urban air quality. Importantly, decisions on GI4AQ must be made in the wider context of all the costs and benefits of trees (and other GI) in cities (Daniels et al. 2018 ), for example as one component of a wider “Urban Tree Score” Framework (Donovan et al. 2005 ).

Finally, it should be noted that the most direct and sure way to improve urban air quality is by reducing primary pollutant emissions and the focus of air pollution policies should always be on this. As a secondary measure, it is always beneficial simply to extend the distance between sources and receptors at all horizontal scales. Introducing GI4AQ should therefore normally be considered a third-best measure that may, in some situations, help improve urban air quality.

Abhijith, K.V., P. Kumar, J. Gallagher, A. McNabola, R. Baldauf, F. Pilla, B. Broderick, S. Di Sabatinoi, and B. Pulvirenti. 2017. Air pollution abatement performances of green infrastructure in open road and built-up street canyon environments—A review. Atmospheric Environment 162: 71–86.

Article   CAS   Google Scholar  

Atkinson, R.A., and J. Arey. 2003. Gas-phase tropospheric chemistry of biogenic volatile organic compounds: A review. Atmospheric Environment 37: S197–S219.

Baldauf, R. 2017. Roadside vegetation design characteristics that can improve local, near-road air quality. Transportation Research Part D Transport and Environment 843: 354–361.

Article   Google Scholar  

Baltaxe, R. 1967. Air flow patterns in the lee of model windbreaks. Archiv für Meteorologie, Geophysik und Bioklimatologie 15: 287–312.

Barnes, M.J., T. Brade, A.R. MacKenzie, J.D. Whyatt, D.J. Carruthers, J. Stocker, X. Cai, and C.N. Hewitt. 2014. Spatially-varying surface roughness and ground-level air quality in an operational dispersion model. Environmental Pollution 185: 44–51.

Beatley, T. 2016. Handbook of Biophilic City Planning and Design . Washington, DC: Island Press.

Book   Google Scholar  

Berardi, U., A.H. GhaffarianHoseini, and G. Hoseini. 2013. State-of-the-art analysis of the environmental benefits of green roofs. Journal of Applied Energy 115: 411–428.

Biogenic Volatile Organic Compounds (BVOC) Data. http://bai.acom.ucar.edu/Data/BVOC/ . Accessed 1 June 2017.

Biogenic Volatile Organic Compounds (BVOC) Database. http://www.es.lancs.ac.uk/cnhgroup/iso-emissions.pdf . Accessed 1 June 2017.

Bowker, G.E., R. Baldauf, V. Isakov, A. Khlystov, and W. Petersen. 2007. The effects of roadside structures on the transport and dispersion of ultrafine particles from highways. Atmospheric Environment 41: 8128–8139.

Bradley, E.F., and P.J. Mulhearn. 1983. Development of velocity and shear stress distribution in the wake of a porous shelter fence. Journal of Wind Engineering and Industrial Aerodynamics 15: 145–156.

Branford, D., D. Fowler, and M.V. Moghaddam. 2004. Study of aerosol deposition at a wind exposed forest edge using 210 Pb and 137 Cs soil inventories. Water, Air, and Soil Pollution 157: 107–116.

Cabaraban, M.T.I., C.N. Kroll, S. Hirabayashi, and D.J. Nowak. 2013. Modeling of air pollutant removal by dry deposition to urban trees using a WRF/CMAQ/i-Tree Eco coupled system. Environmental Pollution 176: 123–133.

Calfapietra, C., S. Fares, F. Manes, G. Sgrigna, and F. Loreto. 2013. Role of Biogenic Volatile Organic Compounds (BVOC) emitted by urban trees on ozone concentration in cities: A review. Environmental Pollution 183: 71–80.

Calfapietra, C., J. Peñuelas, and Ü. Niinemets. 2015. Urban plant physiology: Adaptation-mitigation strategies under permanent stress. Trends in Plant Science 20: 72–75.

Carlton, A.G., C. Wiedinmyer, and J.H. Kroll. 2009. A review of Secondary Organic Aerosol (SOA) formation from isoprene. Atmospheric Chemistry and Physics 9: 4987–5005.

Chameides, W.L., R. Linsay, R. Richardson, and C. Kiang. 1988. The role of biogenic hydrocarbons in urban photochemical smog: Atlanta as a case study. Science 241: 1473–1475.

Choi, W., A.M. Winer, and S.E. Paulson. 2014. Factors controlling pollutant plume length downwind of major roadways in nocturnal surface inversions. Atmospheric Chemistry and Physics 14: 6925–6940.

Daniels, B., B.S. Zaunbrecher, B. Paas, R. Ottermanns, M. Ziefle, and M. Roß-Nickoll. 2018. Assessment of urban green space structures and their quality from a multidimensional perspective. Science of the Total Environment 615: 1364–1378.

Design Manual for Roads and Bridges (DMRB), volume 11, section 3, part 1, ha20707. http://www.standardsforhighways.co.uk/ha/standards/dmrb/ . Accessed 1 May 2017.

Donovan, R.G., C.N. Hewitt, H.E. Stewart, S.M. Owen, and A.R. MacKenzie. 2005. Development and application of an Urban Tree Air Quality Score for photochemical pollution episodes using the Birmingham, United Kingdom, area as a case study. Environmental Science and Technology 39: 6730–6738.

Estrada, F., W.J.W. Botzen, and R.S.J. Tol. 2017. A global economic assessment of city policies to reduce climate change impacts. Nature Climate Change 7: 403–406.

Fowler, D., U. Skiba, E. Nemitz, F. Choubedar, D. Branford, and R. Donovan. 2004. Measuring aerosol and heavy metal deposition on urban woodland and grass using inventories of 210 Pb and metal concentrations in soil. Water, Air, and Soil Pollution 4: 483–499.

Fowler, D., M. Amann, F. Anderson, M. Ashmore, P. Cox, M. Depledge, D. Derwent, P. Grennfelt, et al. 2008. Ground - Level Ozone in the 21st Century: Future Trends, Impacts and Policy Implications. Royal Society Policy Document 15/08, RS1276 edn. London: The Royal Society.

Fowler, D., K. Pilegaard, M.A. Sutton, P. Ambus, M. Raivonen, J. Duyzer, D. Simpson, H. Fagerli, et al. 2009. Atmospheric composition change: Ecosystems–atmosphere interactions. Atmospheric Environment 43: 5193–5267.

Gallagher, J., R.W. Baldauf, C. Fuller, P. Kumar, L. Gill, and A. McNabola. 2015. Passive methods for improving air quality in the built environment: A review of porous and solid barriers. Atmospheric Environment 120: 61–70.

Gromke, C., and B. Blocken. 2015. Influence of avenue-trees on air quality at the urban neighborhood scale. Part II: Traffic pollutant concentrations at pedestrian level. Environmental Pollution 196: 176–184.

Gromke, C., N. Jamarkattel, and B. Ruck. 2016. Influence of roadside hedgerows on air quality in urban street canyons. Atmospheric Environment 139: 75–86.

Gröte, R., R. Samson, R. Alonso, J.H. Amorim, P. Cariñanos, G. Churkina, S. Fares, D. Le Thiec, Ü. Niinemets, T.N. Mikkelsen, E. Paoletti, A. Tiwary, and C. Calfapietra. 2016. Functional traits of urban trees: Air pollution mitigation potential. Frontiers in Ecology and the Environment 14: 543–550.

Guenther, A.B., X. Jian, C.L. Heald, T. Sakulyanontvittaya, T. Duhl, L.K. Emmons, and X. Wang. 2012. The Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1): An extended and updated framework for modeling biogenic emissions. Geoscientific Model Development 5: 1471–1492.

Guenther, A., C.N. Hewitt, D. Erickson, R. Fall, C. Geron, T. Graedel, P. Harley, L. Klinger, et al. 1995. A global model of natural volatile organic compound emissions. Journal of Geophysical Research 100: 8873–8892.

Guidolotti, G., C. Calfapietra, E. Pallozzi, G. De Simoni, R. Esposito, M. Mattioni, G. Nicolini, G. Matteucci, et al. 2017. Promoting the potential of flux-measuring stations in urban parks: An innovative case study in Naples, Italy. Agricultural and Forest Meteorology 233: 153–162.

Guo, L., and R.G. Maghirang. 2012. Numerical simulation of air flow and particle collection by vegetative barriers. Engineering Applications of Computational Fluid Mechanics 6: 110–112.

Hale, J.D., T.A.M. Pugh, J.P. Sadler, C.T. Boyko, J. Brown, S. Caputo, M. Caserio, R. Coles, et al. 2015. Delivering a multi-functional and resilient urban forest. Sustainability 7: 4600–4624.

Hallquist, M., J.C. Wenger, U. Baltensperger, Y. Rudich, D. Simpson, M. Claeys, J. Dommen, N.M. Donahue et al. 2009. The formation, properties and impact of secondary organic aerosol: Current and emerging issues. Atmospheric Chemistry and Physics 9: 5155–5236.

Hatanaka, A. 1993. The biogeneration of green odor by green leaves. Phytochemistry 34: 1201–1218.

Heist, D., V. Isakov, S. Perry, M. Snyder, A. Venkatram, C. Hood, J. Stocker, D. Carruthers, et al. 2013. Estimating near-road pollutant dispersion: A model inter-comparison. Transportation Research Part D Transport and Environment 25: 93–105.

Henderson, V., A.J. Venables, T. Regan, and I. Samsonov. 2016. Building functional cities. Science 352: 946–947.

Hofman, J., H. Bartholomeus, S. Janssen, K. Calders, K. Wuyts, S. Van Wittenberghe, and R. Samson. 2016. Influence of tree crown characteristics on the local PM 10 distribution inside an urban street canyon in Antwerp (Belgium): A model and experimental approach. Urban Forestry and Urban Greening 20: 265–276.

i-Tree Canopy v6.1. Estimate tree cover and tree benefits for a given area with a random sampling process that lets you easily classify ground cover types . https://canopy.itreetools.org/ . Accessed 1 April 2018.

Jacobson, M.Z., W.G. Colella, and D.M. Golden. 2005. Cleaning the air and improving health with hydrogen fuel-cell vehicles. Science 308: 1901–1905.

Janhäll, S. 2015. Review on urban vegetation and particle air pollution—Deposition and dispersion. Atmospheric Environment 105: 130–137.

Jeanjean, A.P.R., R. Buccolieri, J. Eddy, P.S. Monks, and R.J. Leigh. 2017a. Air quality affected by trees in real street canyons: The case of Marylebone neighbourhood in central London. Urban Forestry and Urban Greening 22: 41–53.

Jeanjean, A.P.R., J. Gallagher, P.S. Monks, and R.J. Leigh. 2017b. Ranking current and prospective NO 2 pollution mitigation strategies: An environmental and economic modelling investigation in Oxford Street, London. Environmental Pollution 225: 587–597.

Jeanjean, A.P.R., G. Hinchliffe, W.A. McMullan, P.S. Monks, and R.J. Leigh. 2015. A CFD study on the effectiveness of trees to disperse road traffic emissions at a city scale. Atmospheric Environment 120: 1–14.

Keenan, T.F., Ü. Niinemets, S. Sabata, C. Gracia, and J. Peñuelas. 2009. Process based inventory of isoprenoid emissions from European forests: Model comparisons, current knowledge and uncertainties. Atmospheric Chemistry and Physics 9: 4053–4076.

King, E.A., E. Murphy, and A. McNabola. 2009. Reducing pedestrian exposure to environmental pollutants: A combined noise exposure and air quality analysis approach. Transportation Research Part D Transport and Environment 14: 309–316.

Langford, B., E. Nemitz, E. House, G.J. Phillips, D. Fasmulari, B. Davison, J.R. Hopkins, A.C. Lewis, and C.N. Hewitt. 2010. Fluxes and concentrations of volatile organic compounds above central London, UK. Atmospheric Chemistry and Physics 10: 627–645.

Laothawornkitkul, J., J.E. Taylor, N.D. Paul, and C.N. Hewitt. 2009. Biogenic volatile organic compounds in the Earth system. New Phytologist 183: 27–51.

Livesley, S.J., E.G. McPherson, and C. Calfapietra. 2016. The urban forest and ecosystem services: Impacts on urban water, heat, and pollution cycles at the tree, street, and city scale. Journal of Environmental Quality 45: 119–124.

Lombardi, D.R., J.M. Leach, C.D.F. Rogers, and The Urban Futures Team. 2012. Designing Resilient Cities: A Guide to Good Practice . Bracknell: IHS BRE Press.

Google Scholar  

Lu, J.W.T., E.S. Svendsen, L.K. Campbell, J. Greenfield, J. Braden, K. King, and N. Faixa-Raymond. 2010. Biological, social, and urban design factors affecting young street tree mortality in New York City. Cities and the Environment 3: 1–15.

MacKenzie, A.R., R.M. Harrison, I. Colbeck, and C.N. Hewitt. 1991. The role of biogenic hydrocarbons in the production of ozone in urban plumes in southeast England. Atmospheric Environment 25: 351–359.

McNabola, A., B.M. Broderick, and L.W. Gill. 2009. A numerical investigation of the impact of low boundary walls on pedestrian exposure to air pollutants in urban street canyons. Science of the Total Environment 407: 760–769.

Mentel, T.F., J. Wildt, A. Kiendler-Scharr, E. Kleist, R. Tillmann, M. Dal Maso, R. Fisseha, T. Hohaus,et al. 2009. Photochemical production of aerosols from real plant emissions. Atmospheric Chemistry and Physics 9: 4387–4406.

Moeller, E. 2015. Suggestions for the Skyscrapers of tomorrow—International Highrise Award 2014. Stahlbau 84: U139–U195.

Moradpour, M., H. Afshin, and B. Farhanieh. 2017. A numerical investigation of reactive air pollutant dispersion in urban street canyons with tree planting. Atmospheric Pollution Research 8: 1–14.

Morani, A., D.J. Nowak, S. Hirabayashi, and C. Calfapietra. 2011. How to select the best tree planting locations to enhance air pollution removal in the MillionTreesNYC Initiative. Environmental Pollution 159: 1040–1047.

Neft, I., M. Scungio, N. Culver, and S. Singh. 2016. Simulations of aerosol filtration by vegetation: Validation of existing models with available lab data and application to near-roadway scenario. Aerosol Science and Technology 50: 937–946.

Ng, W.-Y., and C.-K. Chau. 2012. Evaluating the role of vegetation on the ventilation performance in isolated deep street canyons. International Journal of Environment and Pollution 50: S98–S110.

Nowak, D.J., and D.E. Crane. 2002. Carbon storage and sequestration by urban trees in the USA. Environmental Pollution 116: 381–389.

Nowak, D., D.E. Crane, and J.C. Stevens. 2006. Air pollution removal by urban trees and shrubs in the United States. Urban Forestry and Urban Greening 4: 115–123.

Nowak, D.J., S. Hirabayashi, A. Bodine, and R. Hoehna. 2013. Modeled PM 2.5 removal by trees in ten US cities and associated health effects. Environmental Pollution 178: 395–402.

Oke, T.R. 1988. Street design and urban canopy layer climate. Energy and Buildings 11: 103–113.

Owne, S.M., A.R. MacKenzie, R.G.H. Bunce, H.E. Stewart, R.G. Donovan, G. Stark, and C.N. Hewitt. 2006. Classifying urban land for stratified sampling and surveys, using Principal Component Analysis with quantified uncertainties. Landscape and Urban Planning 78: 311–321.

Padro, J. 1996. Summary of ozone dry deposition velocity measurements and model estimates over vineyards, grass and deciduous forests in summer. Atmospheric Environment 30: 2363–2369.

Pincetl, S., T. Gillespie, D.E. Pataki, S. Saatchi, and J.-D. Saphores. 2013. Urban tree planting programs, function or fashion? Los Angeles and urban tree planting campaigns. GeoJournal 78: 475–493.

Prather, M., and A.H. Jaffe. 1990. Global impact of the Antarctic ozone hole: Chemical propagation. Journal of Geophysical Research 95: 3473–3492.

Pugh, T.A.M., A.R. MacKenzie, J.D. Whyatt, and C.N. Hewitt. 2012. The effectiveness of green infrastructure for improvement of urban air quality. Environmental Science and Technology 46: 7692–7699.

Raine, J.K., and D.C. Stevenson. 1977. Wind protection by model fences in a simulated atmospheric boundary layer. Journal of Wind Engineering and Industrial Aerodynamics 2: 159–180.

Ratti, C., S. Di Sabatino, and R. Bitter. 2006. Urban texture analysis with image processing techniques: Wind and dispersion. Theoretical and Applied Climatology 84: 77–99.

Salmond, J.A., M. Tadaki, S. Vardoulakis, K. Arbuthnott, A. Coutts, M. Demuzere, K.N. Dirks, C. Heaviside, S. Lim, H. Macintyre, R.N. McInnes, and B.W. Wheeler. 2016. Health and climate related ecosystem services provided by street trees in the urban environment. Environmental Health 15: 36.

Schiermeier, Q. 2015. The science behind the Volkswagen emissions scandal. Nature . https://doi.org/10.1038/nature.2015.18426 .

Sehmel, G.A. 1980. Particle and gas deposition: A review. Atmospheric Environment 14: 983–1011.

Sillman, S. 1999. The relation between ozone, NO x and hydrocarbons in urban and polluted rural environments. Atmospheric Environment 33: 1821–1845.

Speak, A.F., J.J. Rothwell, S.J. Lindley, and C.L. Smith. 2012. Urban particulate pollution reduction by four species of green roof vegetation in a UK city. Atmospheric Environment 61: 283–293.

Specifind: developed by Cost FP1024 GreenInUrbs: Nature based solutions for sustainable and resilient cities. http://www.greeninurbs.com/p_specifind/ . Accessed 1 Oct 2017.

Stocker, J., D. Heist, C. Hood, V. Isakov, D. Carruthers, S. Perry, M. Snyder, A. Venkatram, et al. 2013. Road source model intercomparison study using new and existing datasets. In 15th International Conference on Harmonisation , Madrid, Spain. http://www.harmo.org/Conferences/Proceedings/_Madrid/publishedSections/H15-78.pdf . Accessed 3 Jan 2019.

Tan, D.G.H., P.H. Haynes, A.R. MacKenzie, and J.A. Pyle. 1998. Effects of fluid dynamical stirring and mixing on the deactivation of stratospheric chlorine. Journal of Geophysical Research 103: 1585–1605.

Tiwary, A., H.P. Morvan, and J.J. Colls. 2005. Modelling the size-dependent collection efficiency of hedgerows for ambient aerosols. Journal of Aerosol Science 37: 990–1015.

Tong, Z., R.W. Baldauf, V. Isakov, P. Deshmukh, and K.M. Zhang. 2016. Roadside vegetation barrier designs to mitigate near-road air pollution impacts. Science of the Total Environment 541: 920–927.

Treeconomics. 2015. Valuing London’s Urban Forest: Report of the London iTree Eco Project . https://www.forestry.gov.uk/pdf/LONDONI-TREEECOREPORT151202.pdf/$FILE/LONDONI-TREEECOREPORT151202.pdf . Accessed 3 Jan 2019.

Trees, Design and Action Group (TDAG). 2012. Trees in the Townscape: A Guide for Decision Makers . http://www.tdag.org.uk/trees-in-the-townscape.html . Accessed 3 Jan 2019.

Trees, Design and Action Group (TDAG). 2014. Trees in Hard Landscapes: A Guide for Delivery . http://www.tdag.org.uk/trees-in-hard-landscapes.html . Accessed 3 Jan 2019.

van den Hurk, B.J.J.M., P. Viterbo, and O.L. Sietse. 2003. Impact of leaf area index seasonality on the annual land surface evaporation in a global circulation model. Journal of Geophysical Research 108: 4191.

Vos, P.E.J., B. Maiheu, J. Vankerkom, and S. Janssen. 2013. Improving local air quality in cities: To tree or not to tree? Environmental Pollution 183: 113–122.

Wang, J.-L., C. Chew, C.-Y. Chang, W.-C. Liao, S.-C. Candice Lung, W.-N. Chen, P.-J. Lee, P.-H. Lin, et al. 2013. Biogenic isoprene in subtropical urban settings and implications for air quality. Atmospheric Environment 79: 369–379.

World Health Organisation. 2016. Ambient Air Pollution: A Global Assessment of Exposure and Burden of Disease . http://apps.who.int/iris/bitstream/10665/250141/1/9789241511353-eng.pdf . Accessed 3 Jan 2019.

Wyche, K.P., A.C. Ryan, C.N. Hewitt, M.R. Alfarra, G. McFiggans, T. Carr, P.S. Monks, K.L. Smallbone, et al. 2014. Emissions of biogenic volatile organic compounds and subsequent photochemical production of secondary organic aerosol in mesocosm studies of temperate and tropical plant species. Atmospheric Chemistry and Physics 14: 12781–12801.

Yang, J., J. McBride, J. Zhou, and Z. Sun. 2005. The urban forest in Beijing and its role in air pollution reduction. Urban Forestry and Urban Greening 3: 65–78.

Yang, J., Q. Yu, and P. Gong. 2008. Quantifying air pollution removal by green roofs in Chicago. Atmospheric Environment 42: 7266–7273.

Young, R.F. 2011. Planting the living city: Best practices in planning green infrastructure—Results from major US cities. Journal of the American Planning Association 77: 368–381.

Download references

Acknowledgements

We acknowledge support from Lancaster University and from a Royal Society Wolfson Research Merit Award (CNH); a Royal Society Dorothy Hodgkins Research Fellowship (KA); the European Research Council through the FASTER Project (Project ID 320821) and the Natural Environment Research Council (NERC) through the CityFlocks Project (NE/N003195/1) (A.R.M.K.). We thank Emma Ferranti (University of Birmingham), who is funded by an NERC Knowledge Exchange Fellowship, for assistance with our dissemination plan. We thank Studio Signorella and http://Reduction.org for the design and production of figures.

Author information

Authors and affiliations.

Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK

C. Nick Hewitt & Kirsti Ashworth

Birmingham Institute for Forest Research and School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK

A. Rob MacKenzie

You can also search for this author in PubMed   Google Scholar

Corresponding author

Correspondence to C. Nick Hewitt .

Additional information

Publisher's note.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/ ), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Reprints and permissions

About this article

Hewitt, C.N., Ashworth, K. & MacKenzie, A.R. Using green infrastructure to improve urban air quality (GI4AQ). Ambio 49 , 62–73 (2020). https://doi.org/10.1007/s13280-019-01164-3

Download citation

Received : 04 October 2018

Revised : 04 February 2019

Accepted : 27 February 2019

Published : 16 March 2019

Issue Date : January 2020

DOI : https://doi.org/10.1007/s13280-019-01164-3

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

  • Air pollution
  • Air quality
  • Green infrastructure
  • Urban environment
  • Find a journal
  • Publish with us
  • Track your research

Don't miss tomorrow's smart cities industry news

Let Smart Cities Dive's free newsletter keep you informed, straight from your inbox.

site logo

3 ways smart cities can improve air quality

With urbanites expressing a renewed interest in air quality improvement amid the coronavirus, cities may find themselves in need of better data to base policy decisions.

Editor's Note: The following is a guest post from Grant Samms, research analyst at Guidehouse Insights.

The collective realization about our acceptance of polluted air has been one of the most spectacular realities unveiled by the new coronavirus pandemic (COVID-19). As personal vehicle miles fell dramatically, skies in the world’s largest cities turned a shade of blue that astonished many residents. While skies cleared, researchers discovered that exposure to poor air quality could increase susceptibility to the coronavirus.

As parts of the world return to a resemblance of pre-lockdown status, there is discussion about not letting this improvement in air quality slip quietly into the history books. With urbanites around the world expressing a strong and renewed interest in improving air quality, cities might find themselves in need of better air quality data on which to base new policy decisions.

Luckily, the past five years have seen tremendous leaps forward in air quality sensing for smart cities. When gathering air quality data, smart cities should consider the following recommendations:

1. Increase data resolution

To improve air quality, cities must first achieve greater data resolution. Historically, air quality for an entire city has been measured at one or two geographic points for regulation compliance. However, concentrations of pollutants can change significantly over just a few city blocks, so measurements must be collected from many strategically chosen locations.

The past few years have seen the development of air quality sensors that are smaller, more automated and much less expensive than the regulatory sensors of old. These new sensors can be mounted to existing infrastructure and constantly communicate levels of up to a dozen pollutants through the internet of things (IoT). True, they may not have the accuracy of their larger brethren, but today's IoT sensors are getting pretty close.

Cities have options beyond physically deployed sensors, though they come with their own drawbacks. Cities can contract mobile surveying, which will give a much larger profile across geographic space at the cost of a less complete profile over time. Typically, these surveys involve sensors mounted to cars, but there are examples of cities using bike-share bikes, municipal trucks and even drones for mobile measurement.

Alternatively, cities could purchase access to one of the air quality models being pioneered by environmental data companies. These companies take data from existing air quality sensors and fill in the gaps with fluid dynamics models that account for weather conditions, traffic patterns and historic conditions to predict air quality for any point. Given the small pool of air quality data this method draws from, there are concerns about its accuracy. However, it is an inexpensive option.

2. Understand air quality sensors' ROI

Once a city has settled on a measurement technology, they must face the quintessential question for any municipal project: how do we pay for this? This question is a bit more difficult to answer for air quality monitoring than, say, smart street lighting. For the latter, you can model the energy savings and calculate a clear timeline for ROI, which makes the decision to cut the check much easier.

Cities have struggled to draw such a clear picture for air quality monitoring. One way to envision ROI is to quantify the macroeconomic gains when the people in a city spend less time sick due to asthma, emphysema and other respiratory conditions. Air pollution has a quantifiable economic cost: roughly $900 billion or 5% of US GDP annually, according to a 2019 study in the Proceedings of the National Academy of Sciences.

There may be other ways for cities to realize returns on their air quality sensing expenditures. As previously mentioned, air quality modeling companies depend on physically sensed data as the foundation of their modeling projections. The more data points they can gather, the more accurate their models will be. Cities could use the market for licensing this kind of data to gain a financial return on their IoT air quality network.

Other opportunities exist around data licensing, such as real estate development companies that are interested in proving good air quality as part of their project proposals.

3. Find innovative data uses

Once an air quality sensor network is in place, cities can use the data for much more than determining whether the air is good or bad on a given day. For example, the city of Leeds in the U.K. is combining air quality sensing and geofencing to automatically switch the city’s fleet of hybrid vehicles to electric-only mode when they enter areas with poor air. This approach helps dissipate these bad air patches, and vehicles can resume normal hybrid operation once they are out of the bad patch.

The city of Coventry in the United Kingdom is using air quality sensors to display messages that encourage drivers and pedestrians entering areas with high air pollution levels, to consider alternative routes. It's not difficult to imagine versions of this system where, instead of merely suggesting alternative routes, the behavior of traffic infrastructure is automatically altered to limit the number of drivers in a city’s most polluted areas.

Although it might be difficult to define an air quality sensor network's place in the smart city, innovative communities are showing that place does exist. The coronavirus crisis has demonstrated the importance of improving air quality instead of dismissing it as something that is nice to have. As technologies that measure and act on air quality data become more accessible, cities need to exhibit innovative thinking about how they use these tools for the betterment of urban life.

Smart Cities Dive news delivered to your inbox

Get the free daily newsletter read by industry experts

  • Select user consent: By signing up to receive our newsletter, you agree to our Terms of Use and Privacy Policy . You can unsubscribe at anytime.

Daily Dive newsletter example

Editors' picks

Image attribution tooltip

Drones are changing emergency response in this Pacific Northwest city

Bellevue, Washington, has used drones to monitor crowd safety on Independence Day, locate a person fleeing arrest and photograph a car crash scene.

3 ways Washington cities are reimagining downtowns

Facing empty offices and shops and less pedestrian activity, these cities are seizing the opportunity for creative placemaking.

Keep up with the story. Subscribe to the Smart Cities Dive free daily newsletter

Company Announcements

TerraGo Technologies logo

Want to share a company announcement with your peers?

Get started ➔

  • Building decarbonization guide to be developed by ASHRAE, Noresco By Nish Amarnath
  • Chicago sues oil, gas companies to make them pay for climate deception By Ysabelle Kempe
  • Infrastructure law may increase transportation’s GHG emissions as states spend more on highways By Dan Zukowski
  • For US aerial trams, the sky’s the limit By Adina Solomon

How Cities Can Effectively Improve Air Quality

Giving compass' take:.

  •  Grant Samms shares three recommendations on how smart cities can move forward on improving air quality in urban centers.
  • How can donors participate in improving air quality? What role can you play?
  • Read about air quality emissions regulations .

What is Giving Compass?

We connect donors to learning resources and ways to support community-led solutions. Learn more about us .

The collective realization about our acceptance of polluted air has been one of the most spectacular realities unveiled by the new coronavirus pandemic (COVID-19). As personal vehicle miles fell dramatically, skies in the world’s largest cities turned a shade of blue that astonished many residents. While skies cleared, researchers discovered that exposure to poor air quality could increase susceptibility to the coronavirus.

As parts of the world return to a resemblance of pre-lockdown status, there is discussion about not letting this improvement in air quality slip quietly into the history books. With urbanites around the world expressing a strong and renewed interest in improving air quality, cities might find themselves in need of better air quality data on which to base new policy decisions.

Luckily, the past five years have seen tremendous leaps forward in air quality sensing for smart cities. When gathering air quality data, smart cities should consider the following recommendations:

  • Increase data resolution  To improve air quality, cities must first achieve greater data resolution. Historically, air quality for an entire city has been measured at one or two geographic points for regulation compliance. However, concentrations of pollutants can change significantly over just a few city blocks, so measurements must be collected from many strategically chosen locations.
  • Understand air quality sensors' ROI  Once a city has settled on a measurement technology, they must face the quintessential question for any municipal project: how do we pay for this? This question is a bit more difficult to answer for air quality monitoring than, say, smart street lighting.
  • Find innovative data uses  Once an air quality sensor network is in place, cities can use the data for much more than determining whether the air is good or bad on a given day.

Read the full article about air quality by Grant Samms at Smart Cities Dive.

More Articles

These google streetview cars are now mapping and measuring pollution, fast company, jun 29, 2017, cities should monitor air quality for urban planning and public health, smart cities dive, aug 10, 2021.

Become a newsletter subscriber to stay up-to-date on the latest Giving Compass news.

Giving Compass Network

Partnerships & services.

We are a nonprofit too. Donate to Giving Compass to help us guide donors toward practices that advance equity.

Trending Issues

Copyright © 2024, Giving Compass Network

A 501(c)(3) organization. EIN: 85-1311683

  • Reykjavik, Iceland
  • Vaxjo, Sweden
  • Freiburg, Germany
  • Oslo, Norway
  • Copenhagen, Denmark
  • Vancouver, Canada
  • London, England
  • Curitiba, Brazil
  • Portland, Oregon
  • San Diego, California
  • What Makes a City Sustainable
  • 5 Greenest US Cities
  • Sustainability Defined
  • Sustainable Urban Planning
  • Desalination in San Diego, Israel, and Worldwide
  • Featured Sustainable City: Chicago
  • Featured Sustainable City: New York City
  • Geothermal District Heating in Iceland
  • London Olympics
  • Paris: CRIT’Air
  • Passivhaus in Vaxjo
  • Recycling in Curitiba
  • Featured Sustainable City: Vancouver and the GCAT
  • The Greenest Town in Europe
  • Featured Sustainable City: Austin
  • Green City Solutions: Reykjavik
  • Vancouver: Sustainable Transit Capital of North America
  • Renewable Energy – Global Electricity Mix
  • Breakthroughs in Solar
  • The Average Payback Period for Solar Panels
  • 3 Benefits of Solar Energy + Installation Tips
  • Community Solar & Net Metering
  • Topaz Solar Farm
  • Ivanpah Solar Electric Generating System
  • Kamuthi Solar Power Project
  • Bhadla Solar Park
  • 6 Reasons to Go Solar
  • Breakthroughs in Wind
  • London Array
  • Anholt Wind Farm
  • Amazon RE Projects
  • The RISE of SOLAR
  • Block Island and Future US Offshore Wind Farms
  • Anaerobic Digestion and Waste-to-Energy
  • Fuel Solution – Cellulosic Biofuel
  • Gasification – Creating Syngas
  • Algae – the Future of Biofuel
  • HydroPOWER in the USA
  • Hydrokinetic and Marine Energy
  • Feed-In Tariffs, RPS, and Net Metering
  • The Bullitt Center
  • The Cottle Home
  • 5 Examples of Net Zero Buildings Around the World
  • Net Zero Construction
  • Sustainable Construction Management
  • The 3 Best Ways to Reduce the Carbon Footprint in Your Home
  • Creating A Carbon-Free Home
  • Green Building Benefits
  • Energy Star
  • Home Energy Management
  • Flow Meter Technology
  • Home Energy Efficiency
  • 14 Energy Saving Tips + Green Living Tips
  • 10 Best Green Home Tech Items
  • Designing Efficient Buildings
  • Smart Meters Expanding Globally
  • Microgrids: Powering the Future

Smart City Energy Infrastructure

  • Do Cities Need to Change Infrastructure to Become Smarter?
  • Demand Response
  • 5 Ways Construction Companies Can Build Green
  • Managing Construction and Demolition Waste Sustainably
  • How to Sustainably Remodel Your Home: A Guide for Homeowners
  • 10 Tips to Find an Eco-Friendly Contractor
  • European Green Building
  • District Energy
  • 5 Advantages of LEDs
  • Low-Carbon Solutions for Cement and Steel
  • Reducing Emissions From Refrigerants

Clean Hydrogen Power

  • 10+ Point Plan to Reduce GHGs
  • Clean Energy Jobs Are UP
  • Ambitious Net Zero Public Policy
  • Shortfall in International NDCs
  • International Methane Reduction Pledges
  • Nationally Determined Contributions (NDCs) and International Net Zero Goals
  • Sustainability Priorities for Energy, Pipelines, MORE…
  • Global ICE Vehicle Phase-Out
  • Coal-Fired Power Plant Phase-Out
  • How Safe & Clean is Nuclear Energy?
  • Carbon Capture (CCS, DAC, & BECCS)
  • Next-Gen Batteries
  • Batteries – Climate Solution
  • Smart Meters – Smarter Grid for the US, and the World
  • Smart Meter Benefits to Energy Consumers and Utilities
  • Smart Cities Contributing to Sustainable Development
  • Carbon Tax – Pricing Pollution
  • CHP – Making the Most of Energy
  • Natural Gas vs. Coal
  • Hydrogen Buses & H2BusEurope
  • Low-Carbon Shipping Fuels and SAF
  • Sustainable Mass Transit
  • 5 Advantages of LED Lighting
  • 10 Countries Accelerating EVs

EVs and the Future of Urban Transit

  • E-mobility Trends
  • Debunking Electric Car Myths
  • Recycling Global Report Card
  • 10 Ways to Reduce Food Waste
  • 5 Types of Change in Climate
  • Desalination – One H2O Solution
  • Sustainable Agriculture
  • Regenerative Agriculture and Plant-Based Diets
  • Climate Support: Reforestation
  • Zero Waste Circular Economy
  • Decoupling and Divestment
  • Sustainable Waste Management
  • The Best Waste Management Practices
  • How Modern Technologies are Implemented in Smart Cities
  • 10 Simple Steps To Living A Sustainable Lifestyle
  • How to Live a More Sustainable Life
  • Green City Times’ Sustainability Resources
  • Next-Generation Batteries
  • Combined Heat and Power (Cogeneration) – Making the Most of Energy
  • Gasification – Creating Syngas
  • ICE Vehicle Phase-Out
  • Plus-Energy Homes in Vauban, Germany
  • Passivhaus Construction in Växjö, Sweden
  • 10+ IoT and Sustainability Technologies for Smart Cities
  • Making Smart Cities Sustainable
  • 5 Ways Smart HVAC Can Make Smart Cities More Sustainable
  • Smart Cities – Sustainable Development
  • IoT Technologies Implemented in Smart Cities
  • Ride-Sharing – Eco-Friendly Choice
  • California – Current Progress of a Climate Champion
  • Solutions to the European Gas Issue
  • IoT Technology for Air Quality in Smart Cities
  • ESG for Younger Generations
  • Solar Panels Average Payback Period
  • 12 Sustainable Lawn Alternatives to Grass
  • 3 Ways to Inspire Sustainability-Minded Action
  • Reducing Road Pollution
  • Xeriscaping
  • Making Cities a Haven for Wildlife
  • Sustainable Pest Control
  • Benefits of Green Spaces at Home
  • 3 Tips to Enjoy A Fire Sustainably
  • How to Make Your Fitness Routine More Eco-Friendly
  • Social Enterprise Franchising
  • Green E-commerce & Sustainable Packaging
  • Green Signage for Sustainable Cities

GCT - Sustainability | Renewable Energy | Green City Times

Sustainability | Renewable Energy

GCT - Sustainability | Renewable Energy | Green City Times

GREEN Tech for Healthy Air

10 technologies improving air quality in cities  .

by Jane Marsh

Cities are the heart of every global region. They house generations of families, are often headquarters for the world’s biggest companies, and provide universities that produce the most innovative minds. It’s no wonder why so many people throughout the world want to live in a city.

However, an increase in city residents also creates additional air pollution that harms everyone’s health. These are some of the technologies improving air quality in cities to make them better places to live and work.

1. Electric Vehicles

Car, Electric Car, Charging Station

Whether you take a conventionally fueled (fossil fuel-based) bus or drive yourself around the city in a vehicle with an internal combustion engine (ICE), the transportation method will burn gas and create greenhouse gas  emissions (GHGs) tha t intensify global warming. ICE vehicles also create many other forms of pollution that adversely affect public health and the environment.

The number of electric vehicle (EV) models available on the global market keeps increasing each year . More people will have access to vehicles with electric motors that eliminate tailpipe emissions and therefore tailpipe pollution; and which prevent GHGs from entering the planet's atmosphere.

2. Vehicles Designed for Hydrogen Fuel

In addition to EVs, engineers, scientists, and vehicle manufacturers are also developing vehicle motors powered by hydrogen gas . Hydrogen doesn’t create carbon dioxide or harmful emissions when burned, so it would be a 100% clean energy alternative.

Hydrogen fuel cell electric vehicles (FCEVs) produce no tailpipe emissions (other than water vapor), and FCEVs are more efficient than conventional ICE vehicles. The U.S. Department of Energy is leading research to make FCEVs safe, affordable, and environmentally friendly vehicle options.

3. Rentable Electric Bikes

Bicycles are another alternative sustainable technology for transportation purposes. Many cities pave their roads with bike lanes included, and some cities even rent out e-bikes and other electric micro-mobility devices (e-scooters, e-skateboards, etc...) to increase sustainable transit options.

Publicly available or rentable bikes will get people across the few blocks they need to travel without burning fossil fuels. It’s a pollution-free form of transportation that immediately makes the surrounding ai r safer to breathe.

4. Personalized HVAC Systems

Urban airborne pollution also involves everyone’s homes. Every ounce of air in your home can contain up to 40,000 dust mites o r more if the house isn’t clean.

It’s so important to tailor your HVAC unit to your household because some families breathe more air pollutants than others. Getting professional advice will point you toward the most suitable air filters and a cleaning sch edule that will make your system last longer.

5. Construction Site Filtration Machines

Research shows that 23% of urban air pollution originates from ongoing co nstruction projects. This is an especially pressing concern in cities because there’s always ongoing construction.

Massive filtration machines at technologically advanced sites pull air through filters during the workday and push out clean air for workers to breathe. They remove dust and other contaminants that people might breathe while working on the site or walking past.

6. Air Quality Sensors

Sometimes city air is safer to breathe than others, so people can check websites or apps to see the current pollution level where they live. Numerous cities installed air sensors to provide accurate instant readings.

Chicago installed their sensors on lam pposts in 2014 to track four common pollutants like carbon dioxide and particulate matter. The chips will upgrade to add v olatile organic compounds (VOCs) when the technology is available. The ability to upgrade without reinstalling new technologies is one of the many benefits of using emerging tech to improve air quality in cities.

7. Wet Deposition Sprinklers

When it rains or snows over a big city, the water particles capture air pollutants and chemicals before bringing them down to earth. Longer periods of rain in one place capture more pollution, but rain systems have varying lengths and move through regions quickly.

Wet deposition sprinklers recreate this helpful process by operating as long as people need. They’re especially helpful in areas with high amounts of airborne pollution.

8. Biomass Household Stoves

The World Health Organization (WHO) estimates 2.6 billion people cook with kerosene , which puts them at risk of inhaling fatal gases. It’s most common in developing countries, but biomass fuel is an easily accessible alternative. It contains naturally degradable compounds like wood, farming waste, and animal dung. People can access all three components where they live and make the fuel at home.

There is a concern for anyone using biomass stoves long-term. Although the fuel doesn’t create carbon monoxide, it can release carbon dioxide fumes that are poisonous in spaces that lack ventilation. Air cleaning technologies will continue to develop and meet people where they liv e in these regions.

9. Pollution-Vacuuming Pods

Cities with massive highway infrastructure put more focus on airborne pollutants created by vehicles. Many have set up pollution-vacuuming pods that sit under each road in response to that. Pipework connects the pod to the upper street and sucks in air to remove ozone, hydrocarbons, and carbon monoxide.

It’s another new technology that makes city air safer to breathe, especially for pedestrians walking along high-traffic streets.

10. Self-Cleaning Structural Concrete

Concrete buildings are fire-proof and withstand extreme weather, so they’re an optimal urban construction solution. They’r e an even better choice when construction teams use self-cleaning concrete to cover the outer walls and roof. It uses photocatalysis to break down pollutants with sunlight redirec ted off the concrete.

Because this technology can also create urban necessities like parking decks and sidewalks, it’s a widespread pollution solution.

Urban leadership and residents should adopt technologies that improve air quality in cities, such as sustainable transit alternatives and household upgrades. Sustainable technologies make a significant difference in reducing airborne pollutants that harm city residents and the pla net .

Author bio:

Jane works as an environmental and energy writer. She is also the founder and editor-in-chief of

Environment.co

Newyorkpanoramashotfromcentralparkaerialviewin

Additional "technologies" that vastly improve urban air quality are the ancient "technologies" of planting trees and maintaining green spaces - as described in the Green Urban Planning article on GCT. Here's an excerpt from the Green City Times' Urban Planning article:

"Urban roads should feature  natural landscapes  nearby; thus increasing the  positive environmental influence of nature on public health .  Trees  and  green spaces serve to create healthier air by filtering urban pollutants, in addition to providing aesthetic value and numerous other benefits.

Planting trees and other greenery in cities also cool urban environments (as well as other smart urban growth solutions like green and cool roofs), helping to reduce the  heat island effect in cities." [QUOTE FROM  -  greencitytimes.com/urban-planning ]

  • air quality sensors
  • biomass stoves
  • electric vehicles
  • personalized HVAC systems
  • pollution-vacuuming pods
  • self-cleaning concrete
  • sustainability
  • wet deposition sprinklers

More articles

5 ways to integrate electrification, 10 ways to create green spaces for cities, eco-capital – oslo, norway, leave a reply cancel reply.

Save my name, email, and website in this browser for the next time I comment.

This site uses Akismet to reduce spam. Learn how your comment data is processed .

Clean Energy

Future generations of batteries, microgrids spread across africa, clean energy jobs are up, and re cost is down, 10 countries promoting the use of electric vehicles, breakthroughs in onshore and offshore wind energy, isegs – a shining example of concentrated solar power (csp) in california, breakthroughs in solar photovoltaics and solar thermal, offshore wind farms in the united states | block island leads the way, kamuthi solar project, bhadla solar park, and the largest solar pv farms in india and china, energy saving ideas.

  • Install double-pane windows in your home
  • Use CFL or LED light bulbs
  • Use Energy Star labeled equipment
  • Turn off all home and office equipment when not in use, and use power strips for your electricity needs; consider a smart power strip
  • Turn off lights when not in use
  • Turn down the thermostat - lowering it by just one degree can reduce heating energy costs significantly; consider a smart thermostat
  • Avoid unnecessary electricity loads (electrical equipment that still uses energy even after being turned off) by using a power strip
  • Reduce your water heater temperature from 140 degrees to 120 degrees
  • Consider a Home Energy Management system
  • Weatherize and upgrade the insulation in your home
  • Consider adding solar panels to your rooftop, or participating in a community solar program

Climate, Renewable Energy, and Sustainability Resources

  • NOAA Climate  
  • NASA Climate  
  • Breakthrough Energy
  • Yale Environment 360  
  • Yale Climate Connections  
  • MIT Energy Initiative  
  • MIT Climate  
  • Carbon Tracker  
  • Cleantechnica  
  • Renewable Energy World  
  • Renewable Energy Magazine  
  • Inhabitat  
  • DeSmog Blog  
  • The Climate Group  
  • Climate Central  
  • Climate Nexus  
  • Smart Cities Dive  
  • climateaction.org and climateactiontracker.org  
  • insideclimatenews.org  
  • carbonbrief.org  
  • drawdown.org  

Climate Action and International Climate Resources

  • earthjustice.org  
  • citizensclimatelobby.org  
  • priceofoil.org  
  • sierraclub.org  
  • ucsusa.org  
  • greenpeace.org  
  • biologicaldiversity.org  
  • Climate Leadership Council  
  • Intergovernmental Panel on Climate Change (IPCC)  
  • IPCC Data Distribution Center  
  • European Commission (re: Climate Change)  
  • UN Global Goals for Sustainable Development  
  • International Renewable Energy Agency (IRENA)  

Ideas for a Greener Lifestyle

  • Reduce, reuse, recycle
  • Bring reusable shopping bags with you to the grocery store or farmer's market
  • Support your local farmer's market and buy seasonal farmed foods and produce
  • Use eco-friendly cleaning supplies
  • Favor cloth over paper products
  • Choose natural lawn care instead of using pesticides and synthetic fertilizers
  • Consider using biodegradable detergent and oxygen bleach
  • Consider getting in the habit of using  reusable mugs, thermoses, sports bottles,  etc… daily
  • Install low-flow toilets and water-saving faucets
  • Consider bicycling instead of driving if possible...try biking to work or using public transit, where these alternatives are accessible
  • Instead of a conventional car that relies on gasoline, consider a plug-in hybrid or a 100%-electric vehicle

Contact Us: [email protected]

© 2024 Green City Times™, LLC

About Us: about.me/gctimes

Navigation breadcrumbs

4 ways cities are using low-cost sensors to improve air quality, you can’t manage what you can’t measure.

Nine out of ten people breathe dirty air. Air pollution leads to early death and increased disease, while impacting our economies and reducing opportunities for our residents to thrive. The most vulnerable and marginalised communities in our cities are most at risk.

Air quality monitoring is a vital part of a city’s toolbox to improve urban air quality. Some cities have access to data from reference (or “regulatory-grade”) monitors – which are highly accurate but expensive. Other cities have little to no air quality information. 

But a recent increase in more-affordable monitoring technologies has created new opportunities for cities of all resource levels. Diverse cities are using low-cost air quality sensors to monitor air pollution and develop actions to clean their air. 

C40 Cities’ new air quality monitoring report highlights 11 cities that have deployed these sensors: Addis Ababa, Dar es Salaam, Denver, Lima, Lisbon, London, Los Angeles, Mumbai, Paris, Portland, and Quezon City. Here are four ways cities are using low-cost air quality sensors to achieve a range of goals.

1. Understanding pollution risk and air quality levels to meet health standards 

So far, 48 mayors have pledged, in the C40 Clean Air Cities Declaration , to establish baseline air pollution levels and set ambitious targets that meet or exceed national commitments – in line with the World Health Organization’s (WHO) Air Quality Guidelines. The mayors have also committed to implementing new policies and programmes to address the top causes of air pollution emissions.

The WHO Air Quality Guidelines are based on global scientific evidence. When formulating policy targets, governments should consider their own local circumstances carefully before adopting these guidelines directly as legally-based standards.

Low-cost air quality sensors can provide the local baseline evidence that cities need to make the case for reducing emissions. In 2020, Quezon City Local Government partnered with C40 and Clean Air Asia to develop an air quality baseline study to support Mayor Joy Belmonte’s Clean Air Cities Declaration commitments. The baseline results provide insights that can be used to identify opportunities for clean air interventions. These interventions can then be integrated into the city’s air quality management plan to help Quezon City meet WHO air quality guidelines

2. Expanding public awareness while building evidence 

Several cities are using data collected from their sensor monitoring networks to raise public awareness around the risks of pollution exposure. By creating an air quality sensor network, cities can make air quality data easily accessible to residents.

For example, the Breathe London pilot used sensors to evaluate air quality in London’s Ultra Low Emission Zone and School Streets projects. The Breathe London monitors detected changing levels of pollutants in locations far from regulatory monitors, providing new insights into local air quality and the potential for short-term air quality change. 

This hyperlocal air pollution data is published on the Breathe London website to provide Londoners with a real-time picture of air pollution levels on their streets. Organisations, businesses and residents can host a sensor in their preferred location (for a fee). Community groups can apply to host a free sensor in a location of their choosing.

3. Uncovering impacts on marginalised people

Sensor networks can help evaluate air pollution exposure and risk among vulnerable and marginalised communities. The sensors provide important information that can help governments advance solutions to mitigate inequities and protect these communities. 

Los Angeles’s sensor network was designed to empower residents of disadvantaged communities with data through collaborative approaches.

The City of Los Angeles and the 30+ community groups in the Transformative Climate Communities (TCC) Watts Rising collaborative created a hyperlocal air quality monitoring network to provide insights and learnings around one neighbourhood’s air quality. 

The city installed sensors near parks and schools, and ran community outreach initiatives. Vulnerable populations, including children and seniors, were engaged and educated on monitoring air quality. 

In October 2020, the Watts Rising air quality monitoring data portal was launched for residents. Periodic community meetings are being held to allow community members to ask questions about the data.

4. Increasing access to city-scale data and information platforms

The rapidly-expanding lower-cost air quality sensor market presents valuable opportunities for new urban air quality work. But city staff have to navigate many options around sensor selection, network installation and data management. When there is clear communication and collaboration between cities and technology providers, new sensor technologies and data management platforms can more efficiently and effectively help solve urban air quality problems. 

In October 2020, the Addis Ababa Environmental Protection & Green Development Commission (AAEPGDC) and C40 agreed that the city could substantially advance its air quality efforts by owning and operating its own reference-grade monitor. 

C40 and Industrial Economics trained city staff around the maintenance and operations of the monitor as well as a data management system for publicly sharing air quality information. There is now a newly-established AAEPGDC team responsible for air quality monitoring and for processing air quality data to share with the public. The monitor site is being prepared for future sensor co-location studies. 

Recommendations for sensor technology improvements

C40’s report provides recommendations for sensor technology improvements based on technical challenges identified by city staff in C40’s Air Quality Network. Read the report here . 

Related content

how to improve air quality in city

  • 3D Printing
  • Artificial Intelligence
  • Cyber Security
  • Retail & Logistics
  • Robots & Automation
  • Smart Agriculture
  • Smart Lighting
  • Smart Sensors
  • Autonomous Cars
  • Connected Cars
  • Electric Cars
  • Intelligent Transport Systems
  • Public Transport
  • Smart Parking
  • Traffic Management
  • Energy Efficient Lighting
  • Energy Management
  • Renewable Energy
  • Smart Grids
  • Smart Meters
  • Water Conservation
  • Water Management
  • Water Recycling
  • Climate Change
  • Conservation
  • Pollution & Air Quality
  • Waste Management
  • Infrastructure
  • Policy & Regulation
  • Public Services
  • Design & Architecture
  • Green Buildings
  • Nature & Landscaping
  • Safety & Security
  • Smart Furniture
  • Smart Healthcare
  • Smart Homes
  • Town Planning
  • Connected Communities
  • Smart Citizens
  • Smart Education
  • Social Responsibility
  • Partner Events
  • Advertising

SmartCity Press

No More Food Insecurity: How Smart Cities are Making Access to…

Smart cities and the future of smart workplaces, kyiv digital app: driving the city’s well-being, can smart city technology solve urban water shortage problems, the micro and shared mobility evolution – how are we going…, greening up your road trip: best tips to make adventure travel…, making your car eco-friendly in 2023, how smart cities could help us achieve equity and accessibility, embracing eco-friendliness: the environmental benefits of automatic soap dispensers, 8 terrific energy-saving hacks for householders, ssroc and ausgrid shine bright with australia’s largest street lighting upgrade, 8 tips for getting an energy-efficient plumbing system in your home, sustainable fishing destinations we all need to see, going green: simple tips on how to host an eco-friendly event, smart governance: ai tax robots can make tax services more convenient, the smartest cities are centred around their citizens, how smart cities are helping with a better business approach today, sustainable locations you should consider visiting in 2024, things that make natural stone such a sustainable choice for your…, home upgrade: create a sustainable and energy efficient living space, why is natural stone a sustainable choice: the future of construction, the importance of teaching children about sustainability, useful guidelines for sustainable cultural tourism in 2023, how is social media driving the popularity of smart cities, how smart cities can improve the health of people and the….

  • Environment

How Smart Cities Can Improve Air Quality

how to improve air quality in city

Technological advancements have paved the way for smart cities and the term has become quite the buzzword. Smart home technologies have entered the residential space and are also carving out a place in entire municipalities worldwide. 

A smart city leverages advanced technology, such as 5G, the Internet of Things (IoT) and intelligent traffic management systems to increase operational efficiencies and improve citizens’ quality of life. Smart cities are the way of the future and will overcome some of the common challenges being faced today.

One major issue often overlooked before the COVID-19 pandemic was air quality declines. It’s possible that building up smart cities can make significant strides here. 

Smart Cities Already Using Technology to Learn About Air Quality

Cities such as Glasgow, Oakland, Beijing, Hamburg and Manchester have all implemented  various technologies and methods  of collecting data regarding air quality. 

For example, a smog-free tower in Beijing uses only 1,170 watts of energy to clean 30,000 cubic meters of air per hour. 

Google cars embedded with sensors capture data to map air pollution in different city regions in Oakland, California. The mapping exercise found that pollution levels varied between and even within various neighborhoods. It was also found that residents near industrial operations or high-traffic areas were breathing in seven times the amount of toxins as neighbors who only lived one block away.

No matter what technologies cities leverage to monitor air quality, they are more inclined  to learn about air quality and harness big data to serve as a foundation for better decision-making and policies. 

How Smart Cities Improve Air Quality 

Technology continues to advance and smart cities can implement technologies to capture high-quality data about air pollution levels. Before a city can take steps to mitigate these issues, it first needs to gather data from strategically chosen locations.

Generally, air quality  sensors have become smaller , affordable and more automated than before. IoT sensors are widely used in various industries, such as manufacturing, aviation, shipping and logistics. 

It makes sense for smart cities to invest in IoT sensors because they can be mounted to existing buildings and infrastructure and communicate with each other seamlessly. They can also communicate pollutant levels with each other in a given area, allowing city leaders to draw conclusions from that data and identify polluted hotspots.

Consider how even basic smart home technologies are being developed. Even the average consumer can  buy wearables with sensors  to monitor the air quality around them to decide if they want to stay in that area and take on the risks or go elsewhere. 

Another smart city feature that can help improve air quality in a city is the implementation of green public transportation. Greener transportation solutions  can cut back on emissions , making the air quality better and benefiting the environment. 

Challenges Smart Cities Face Monitoring and Improving Air Quality

One challenge a smart city might face when monitoring air quality or taking on an improvement initiative is figuring out these sensors’ return on investment (ROI). How can cities justify the cost? 

A possible solution for this challenge is to quantify the macroeconomic gains of improving air quality. For example, people in smart cities with better air quality may miss fewer workdays because they do not deal with respiratory problems like asthma or emphysema.

Additionally, the more data these sensors gather, the more accurate their air quality monitoring projects will be. Cities may even be able  to license this information  and gain a financial return on their initial investments. 

Another potential challenge a smart city may have to overcome is buy-in from local and state governments. Some leaders may not be interested or willing to support air quality improvement projects or shell out resources to pay for them. 

There’s no one solution to guarantee buy-in from city leaders and government officials, but it’s worth outlining the benefits of improved air quality — especially the economic benefits. Cleaner air may even bolster the tourism industry and keep citizens working during the week. 

It’s understood that millennials and Gen-Zers are  active in the fight against climate change , based on Pew Research Center data. Suppose cities want to keep tourists coming to visit. In that case, they may need to implement air quality improvements to support the tourism and hospitality industries.

Smart Cities Lead to Cleaner Air

It’s expected that most of the world’s population will reside in urban cities in the coming years. Because of this anticipated increase, it’s critical for cities to become smarter and use the latest, innovative technologies to improve air quality. It’ll be interesting to see if smart cities will lead to global air pollution declines in the future.

RELATED ARTICLES MORE FROM AUTHOR

What impact will sustainable cities have on global emission levels, efficient ways to promote sustainability on construction sites, where is air quality analysis heading in 2020, editor picks, how can smart cities become pandemic-proof, popular posts, the new urban policies anticipate a robust future for sydney, innovative solutions for retail and logistics in smart cities, smart property – the rising proptech in smart cities like dubai, popular category.

  • Environment 46
  • Town Planning 39
  • Artificial Intelligence 23
  • Technology 23
  • Climate Change 23
  • Waste Management 20
  • Safety & Security 18
  • Smart Healthcare 18

Upgraded Wood Could Help Cities Achieve Their Sustainability Goals

Published on Voices

Tackling poor air quality: lessons from three cities, karin kemper, sameh wahba, this page in:.

Air pollution poses a major health risk globally, weighing on economies and people’s health. Photo: © aapsky/Shutterstock

How can countries grow their economies and keep air pollution in check at the same time? A new World Bank report explores that tricky question, looking at the kinds of policies and actions three leading cities have taken to tackle poor local air quality, providing lessons for other cities. As we mark World Cities Day on October 31, this research seems more timely than ever.

Air pollution poses a major health risk globally, weighing on economies and people’s health. In 2017, an estimated 4.13 to 5.39 million people died from exposure to PM2.5 – one of the most harmful forms of air pollution.  That’s more than the total number of people who died from HIV/AIDS, tuberculosis, and malaria combined. The cost associated with health impacts of outdoor PM2.5 air pollution is estimated to be US$5.7 trillion, equivalent to 4.8 percent of global GDP, according to World Bank research. The COVID-19 pandemic further highlights why addressing air pollution is so important, with early research pointing to links between air pollution, illness and death due to the virus.  On the flip side, the economic lockdowns caused by the pandemic, while devastating for communities, did result in some noticeable improvements in air quality but these improvements were inconsistent, particularly when it came to PM2.5. Improvements nonetheless show what is possible and provide new impetus for needed change.

“The COVID-19 pandemic further highlights why addressing air pollution is so important, with early research pointing to links between air pollution, illness and death due to the virus.”

Air pollution is especially high in some of the world’s fastest-growing urban areas, caused by a combination of more people, cars, fossil fuel and biomass burning, construction and poor disposal of waste, as well as rapid sprawl.   Agriculture is also an important source, underscoring the multi-faceted and transboundary nature of air pollution. How can cities overcome this issue? The latest World Bank report, Clearing the Air: A Tale of Three Cities , chose Beijing, New Delhi and Mexico City to assess how current and past efforts improved air quality.

Clearing the Air : A Tale of Three Cities

In the early 1990s, Mexico City was known as the world’s most polluted city and while there are still challenges, air quality has vastly improved.  Daily concentration of SO2 – a contributor to PM2.5 concentrations – declined from 300 µg/m3 in the 1990s to less than 100 µg/m3 in 2018.  PM2.5 levels currently are well below the WHO interim target 1 (35 µg/m3).  More recently, Beijing was on a list of the world’s most polluted cities, but with targeted policies and programs, average PM2.5 levels fell from around 90 µg/m3 in 2013 to 58 µg/m3 in 2017.

New Delhi was successful in tackling poor air quality in the late 1990s, implementing an ambitious transportation fuel conversion program that provided some relief to its citizens. Unfortunately, air quality levels have deteriorated since then, leading the national and Delhi state governments to implement new action plans that address multiple sources of pollution. Early indications are that air quality is improving although pollution levels remain worrying high. For example, average PM2.5 levels in 2018 were an unhealthy 128 µg/m3.

From examining the trajectory of these cities, we identified three key elements for success:

Reliable, accessible and real-time information helps create momentum for reform

In Mexico City, careful analysis of the impacts of air pollution on children’s health galvanized public support for the city’s first air quality management strategy. India’s National Air Quality Index program put real time data on pollution levels in the hands of citizens, allowing them to take prevention measures and to demand change. And in Beijing, real time and public data from Continuous Emissions Monitors at industrial locations and power plants helped to hold plant operators and regulators accountable. 

Incentives to local governments, industry and households must be mainstreamed  

Federal governments need to proactively offer incentives to state and city governments to implement air quality management programs.   Failure to provide such incentives in India in the late 1990s resulted in the government developing plans but not implementing them. This led to India’s Supreme Court stepping in to force the government to implement policy measures. A recent government of India program to provide performance-based grants to cities to reward improvements in air quality is a step in the right direction.

Industry and households similarly need incentives. Beijing, for example, used national government funds to provide subsidies for end-of-pipe controls and boiler retrofits in power plants and factories, rebates for scrapping older vehicles and payments to households that replace coal-fired heating stoves for gas or electric systems. Mexico City gave direct subsidies to drivers of old taxis in exchange for retiring and scrapping inefficient vehicles, along with access to low-cost loans to renovate or buy more efficient vehicles. Fiscal incentives and exemptions from emergency restrictions that require industrial plants to curtail their production when air pollution reaches high levels were also introduced.  In the late 1990s, Delhi’s government provided financial incentives to enable 10,000 buses, 20,000 taxis, and 50,000 three-wheelers to convert to Compressed Natural Gas, which has lower emissions than other fossil fuels.

An integrated approach with effective institutions working across sectors and jurisdictions is critical

Air pollution knows no boundaries and requires an airshed-based management perspective. This in turn demands an approach that cuts across jurisdictions and authorities.  The Megalopolis Environment Commission in Mexico brought together federal authorities from the ministries of environment, health, and transport with local authorities from Mexico City and 224 municipalities from the neighboring states of Mexico, Hidalgo, Morelos, Puebla, and Tlaxcala. Together, they jointly defined an airshed for Mexico City, and took coordinated action to improve air quality. Poor air quality comes from many sources – households, rural and urban dwellers, the transport industry, the power sector and agriculture – and an institutional structure is needed that facilitates coordination across all these sectors. In China, the ministries of Environmental Protection (now the Ministry of Ecology and Environment), Industry and Information Technology, Finance, Housing and Rural Development, along with the National Development and Reform Commission and National Energy Administration, worked together to issue a five-year action plan for air pollution prevention and control for the entire Jing-Jin-Ji region that surrounds Beijing and includes the municipality of Beijing, municipality of Tianjin, the province of Hebei, and small parts of Henan, Shanxi, inner Mongolia, and Shandong.

What’s encouraging about this new work is that it shows that with the right policies, incentives and information, air quality can be improved substantially, particularly as countries work to grow back cleaner after the pandemic. There is no silver bullet though and tackling air pollution requires sustained political commitment through comprehensive programs and across sectors.  At the World Bank, we are committed to working with governments as they manage air pollution, providing analytical work, technical assistance and the lending required to support cities to move in the right direction.

Download Report: Clearing the Air: A Tale of Three Cities

The World Bank Group’s Response to the COVID-19 (coronavirus) Pandemic

Karin Kemper's picture

Global Director, Environment, Natural Resources and Blue Economy Global Practice, World Bank

Sameh Wahba's headshot

Regional Director, Sustainable Development, Europe and Central Asia, The World Bank

U.S. flag

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

  • Publications
  • Account settings
  • Advanced Search
  • Journal List
  • J Urban Health
  • v.93(1); 2016 Feb

Logo of jurbhealth

How Can Urban Policies Improve Air Quality and Help Mitigate Global Climate Change: a Systematic Mapping Review

Anne dorothée slovic.

School of Public Health, University of São Paulo, Av. Dr. Arnaldo, 715, São Paulo, SP CEP 01246-90 Brazil

Maria Aparecida de Oliveira

João biehl.

Department of Anthropology and Woodrow Wilson School of Public and International Affairs, Princeton University, 128 Aaron Burr Hall, Princeton, NJ 08544 USA

Helena Ribeiro

Tackling climate change at the global level is central to a growing field of scientific research on topics such as environmental health, disease burden, and its resulting economic impacts. At the local level, cities constitute an important hub of atmospheric pollution due to the large amount of pollutants that they emit. As the world population shifts to urban centers, cities will increasingly concentrate more exposed populations. Yet, there is still significant progress to be made in understanding the contribution of urban pollutants other than CO 2 , such as vehicle emissions, to global climate change. It is therefore particularly important to study how local governments are managing urban air pollution. This paper presents an overview of local air pollution control policies and programs that aim to reduce air pollution levels in megacities. It also presents evidence measuring their efficacy. The paper argues that local air pollution policies are not only beneficial for cities but are also important for mitigating and adapting to global climate change. The results systematize several policy approaches used around the world and suggest the need for more in-depth cross-city studies with the potential to highlight best practices both locally and globally. Finally, it calls for the inclusion of a more human rights-based approach as a mean of guaranteeing of clean air for all and reducing factors that exacerbate climate change.

Introduction

The link between air pollution, cities and climate change.

The debate on anthropogenic atmospheric pollution and climate change has focused largely on its general effects and the sources of certain pollutants but has also begun to address its geographical dimensions. Generally speaking, greenhouse gases (GHGs) are composed of gases such as carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O), and fluorinated gases such as ozone (O 3 ) and chlorofluorocarbons (CFCs) (EPA), while on a local scale, major sources of pollutants include sulfur dioxide (SO 2 ), nitrogen oxide (NO x ), particulate matter (PM), ozone, and lead. These pollutants all damage air quality, but the specific links between their effects on the atmosphere and air quality are a growing field of research. Thus, an increasing number of recent studies have demonstrated the importance of tackling local air pollution as an ally in the effort to cope with and mitigate global climate change. 1 – 3 This phenomenon is particularly important in megacities, defined by the United Nations as cities with more than ten million people 4 , where high levels of both pollutants and people are concentrated. Furthermore, according to the Stern Review, urban centers account for 75 % of the global emissions of GHGs, 5 making cities important hubs of anthropogenic atmospheric pollution and contributors to climate change. Megacities concentrate high levels of fossil fuel emissions from mobile and fixed sources of pollution that contribute to the formation of urban heat island effects 3 , 6 and to global warming. Thus, looking at megacities as experimental hubs 7 to mitigate climate change offers an important opportunity to decrease the effects of global warming and improve air quality. 2

The relationship between air pollution and health has long been studied by scholars, establishing the association between high levels of air pollution and outcomes such as allergies, respiratory disease, and cardiovascular disease. 8 – 12 This health burden is particularly concentrated in urban centers, where it has led to an increase in mortality rates 13 and reduction of life expectancy 14 and has also been associated with economic costs for cities and health systems. 15 Moreover, the impacts of climate change on health are known and have been an important site of research, particularly of how people will adapt and how to mitigate negative effects. 16 , 17 While Molina et al. have previously addressed atmospheric pollution in megacities, 18 it is only in the last decade that urban air pollution and climate change mitigation have been investigated. This raises questions about controlling air quality and understanding its sources.

Air pollution policies have been focused on controlling emissions, improving air quality, and avoiding negative health outcomes. 19 Given the growing need to decelerate the effects of global climate change, urban policy makers have the responsibility to “think global and act local” and to develop interventions that will influence local air quality while also mitigating climate change and adverse health outcomes. Fang et al. have found that “the change in global premature mortality and years of life lost (YLL) associated with changes in surface O-3 and PM2.5” 20 was significant and concluded that stronger emission controls is needed to maintain air quality and reduce the negative effects of climate change on health.

In urban centers, vehicles are one of the primary sources of mobile pollution. 21 Transport vehicles also account for 14 % of global greenhouse emissions and represent an important problem in developing countries. 22 , 23 Privately owned cars also constitute a significant source of emissions in cities that must now prioritize strategies and cope with their negative environmental health outcomes. 24 Vehicle emissions are sources of pollutants such as particulate matter, nitrogen, and ozone that can contribute to global warming. 20 However, there are very few initiatives to manage the effects of air quality on climate change mitigation. 25 As cities become an important site for climate response, 7 mitigation policies for global climate change must focus on the control of air pollutants as a strategy, with particular emphasis on those coming from vehicular emissions.

While the majority of climate-related policies at the national level have focused on GHG emissions, there remains a significant gap regarding policies that address the contribution of vehicular emissions other than CO 2 in cities and how they contribute to global climate change. Existing work has demonstrated the need for integrating both strategies at the local policymaking level. Walsh, for example, has used the example of how diesel control could improve urban air pollution and also help reduce CO 2 . 21 Other studies have attempted to underline the importance of air pollution intervention and its impacts on health and equity, 26 analyzing the impact of heat, air pollution, and co-benefits on mitigation and adaptation. 6 Some papers prioritize air pollution policies or climate change mitigation, 2 , 27 but there are no existing reviews of global urban initiatives taking into consideration both contexts, supporting our hypothesis that air pollution in large urban centers can have a global impact.

In this paper, we present a systematic mapping review of studies that have investigated policies in urban centers aimed at addressing vehicular emissions, supporting the argument that these policies have a significant impact on climate change mitigation as well as on the reduction of local air pollution.

The primary goal of this review is to identify and discuss articles addressing policies to control air pollution in urban milieus, targeting the impacts of vehicle emissions on climate change and local air quality. To this end, we searched for articles that addressed the role of policies focused on reducing mobile sources of air pollution and their effects on climate change mitigation. Selected studies focused on strategies deployed at the local level, which were proven either efficient or non-efficient in reducing air pollution levels and the resulting impacts on climate change, while also identifying policy trends. The methodology used to organize and interpret the data was that of a “systematic mapping review.” Mapping reviews offer the possibility to detect gaps and opportunities within a particular field of research that can assist policy makers in identifying the efficacy of an urban intervention. 28

A systematized search of studies undertaken between the years 2000 and 2015 was performed using the Web of Science (WOS), ProQuest, PubMed, and Scopus databases in three levels, as demonstrated in Fig.  1 . The keywords used for this search were: (“air pollution” OR “atmospheric pollution”) OR “air quality” AND “climate change”) AND (mega* OR city or cities OR urban AND vehicle* OR car* OR traffic OR transport) AND (polic* OR intervention* OR control OR management OR strateg*). The search for each database was adapted as follows: for WOS, the “topic” search field was used; for PubMed, all fields; and for SCOPUS, “titles,” “abstracts,” and “keywords.” Only scholarly articles were considered, and no restrictions on geographic location were applied. In order to avoid duplicates from the four databases, the data were combined at the end of stage one, and all duplicates were eliminated.

An external file that holds a picture, illustration, etc.
Object name is 11524_2015_7_Fig1_HTML.jpg

Overview of the search process.

Selection Process

The process for selecting articles was performed in three stages and can be visualized in Fig.  2 . In the first stage, only titles were looked at, excluding conference abstracts and articles that researched indoor and non-anthropogenic air pollution. Papers whose titles did not apply to the local level were also disregarded. The local level was defined as the “city” or “urban” or “mega city.”

An external file that holds a picture, illustration, etc.
Object name is 11524_2015_7_Fig2_HTML.jpg

Selection process overview.

In the second stage, both titles and abstracts were examined. Here, articles that dealt exclusively with “climate change” and showed no link to vehicle emissions were excluded. In addition, regional studies that looked at urban centers smaller than two million inhabitants were also excluded. The rationale behind this cutoff was that the urban centers studied had to contribute significant emissions in order to have an impact on global climate change, consistent with the hypothesis that air pollution in large urban centers can have a global impact.

In the third and final stage, a full reading of articles and a final selection was conducted. The information from the articles was organized and divided into two tables: (1) articles that provided policy development support, including their expected results, and (2) articles that described post-policy implementation and included an evaluation of accomplished results. Within these two categories, data were organized by source (authors and year of publication), geographic location, type of pollutant, type of policy and recommendations for policy development, and primary findings post-policy. Finally, articles that presented an additional perspective by bringing in a socially inclusive dimension such as “equity” or the “right to clean air” were highlighted.

In terms of the research databases employed, PubMed returned the smallest number of articles (18). Considering the interdisciplinary nature of this research, a potential gap between articles in the fields of environment and health was identified, revealing the need for a stronger interaction between these fields. A potential explanation for this gap is that measuring the effects of mobile sources of air pollution on health requires access and technological “know-how” in order to produce high-quality data on vehicle emissions and levels of air pollutants. This is supported by Fajersztajn et al. who, after a study of air monitoring stations around the world, concluded that information on air pollution monitoring in low-income countries constitutes a major gap and called for a stronger focus on improving data collection as a first step to help reduce its detrimental effects on health. 29

Data were analyzed by year of publication, country, pollutant, and type of policy, following the air pollution management approaches stipulated by the Organization for Economic Co-operation and Development (OECD) classification. 30 In its 2050 Economic Outlook, the OECD classified air policy approaches in three categories: regulatory or command and control (REG), economic instruments (ECO), and others (OTH). REG approaches established rules and standards that aim to reduce air pollution (EPA website). Where this approach takes the form of mandated rules, the second, ECO, is a financially based approach which works via taxes, charges, and financial incentives. The third strategy, OTH, combines initiatives that focus on policy support, such as educational tools, conventions, or other innovative solutions that do not imply any restrictions or financial inputs.

The OECD’s criteria for air pollution management strategies 30 were used to examine the methodologies, recommendations, and primary findings from the selected articles. To each of the three OECD air pollution policy approaches, three sub-classifications were added: (a) circulation-restriction initiatives , (b) alternative initiatives , and (c) technology/fuels approaches. Circulation-restriction initiatives were defined as policies that aim to control vehicle mobility within urban centers. For example, the alternate traffic circulation policy can be considered a restriction initiative. Alternative initiatives are policies that offer alternative forms of mobility in urban centers, such as public transportation, and also include fostering active transportation such as walking or biking. The third sub-classification, technology/fuels initiatives , is aimed at directly improving emissions via technology or the use of alternative fuels. Examples include the use of bioethanol as a fuel or any technological improvement that succeeds in reducing air pollution.

A total 660 articles were obtained from the four different databases under the keyword search criteria; 116 articles were duplicates and 207 articles were excluded after a title screening. After reviewing the abstracts, 108 articles were selected based on criteria for inclusion. Out of these 108 articles, 44 articles dealing with climate factors, health effects, and air pollution were discarded. From these 44, only six articles 31 – 36 established a direct link between vehicular emissions and air pollution, demonstrating the impact of traffic on emission levels. Although not considered here, it is important to highlight that these climate-related articles constitute an opportunity for further research. They offered valuable information on air pollution and its correlation with climate variation (wind, humidity, seasonal trends, urban heat island, heat waves, and global warming), as well as associations between mortality, morbidity, hospital admissions, and the most vulnerable populations. Yet, because they did not explicitly address specific reduction or remediation policies, they were not included in this review.

Thirty-one articles were finally selected for data interpretation. Two texts that analyzed cities smaller than two million inhabitants were included, as one reported on an important pilot project in its country and the other was based in the most important city within the region. One evaluated the efficiency of eco-driving training in Calgary, Canada, 37 while the other measured the co-benefits of the urban public bus system in the city of Yogyakarta, Indonesia, 38 exemplifying a specific initiative that helped improve the transportation system.

The selected articles are categorized in Table ​ Table1, 1 , grouping studies that served as policy support instruments. Table ​ Table2 2 combines those that served as evaluation tools for the efficiency of an implemented policy. Fourteen studies fell into the first category and 17 into the second.

Policy development support—expected results

C CO 2 , CO, CH 4 , and HC; N NO 2 , N 2 O, and NO x ; S SO x ; PM PM 2.5 , PM 10 , black carbon, total particulates; REG regulatory approach; ECO economic incentives; OTH other; A circulation-restriction initiatives; B alternative initiatives; C technology/fuels

Post policy—accomplished results

Drawn from the 31 articles in Tables  1 and ​ and2, 2 , major trends have been identified, as illustrated in Fig.  3 . First, the number of publications is greater in the years 2011 and 2013 (seven for each), and the cities with the highest number of studies are in India (ten), China (seven), and the UK (four). Most case studies located in India are focused in Delhi, which includes New Delhi, 39 – 44 while in China, they are set in Beijing, 3 , 45 – 48 Shenyang, 49 and Chongqing. 47 Of the four articles based in the UK, all of them are situated in London. 43 , 50 – 52 The high number of studies for Delhi and Beijing reflects the severity of the air pollution situation, as they are two of the world’s most polluted cities. On the other hand, London is considered a pioneer in the implementation of control policies for reducing vehicular urban air pollution. The rest of the articles are unevenly distributed around the world, with only three studies in Africa (one in Nigeria and two in South Africa) and few studies in developed countries other than the UK.

An external file that holds a picture, illustration, etc.
Object name is 11524_2015_7_Fig3_HTML.jpg

Overall trends.

The pollutants most frequently assessed were CO 2 (24 articles), CH 4 (14), N 2 O (13), and PM 10 (13), while the least frequently assessed were PM 2.5 (6), SO 2 (5), NO 2 (4), BC (2), SO x (2), TPS (1), and O 3 (1), suggesting that the metering of vehicular control measure efficiency prioritizes reductions of major climate change contributors and not necessarily local pollutants (with the exception of PM 10 ). A more detailed look at the years of publication of these articles shows that an increasing number of studies of carbon-containing pollutants have been performed since 2011. This suggests that there is a growing preoccupation on the part of local policy makers with lowering transport and vehicular emissions, while acknowledging that their policies can contribute to climate change mitigation in addition to local air pollution mitigation.

When the policies were categorized under the OECD classification schema, the policies addressed were evenly distributed between the categories “regulatory” and “others,” which each accounted for 42 %. “Economic instrument” approaches were the least common, comprising only 16 % of policies. These results indicate that regulatory policies are still the most frequently used strategy to control air quality, while “economic instrument” and “other” approaches have the potential to bring innovative solutions to urban air pollution.

The results combined articles that used either qualitative , quantitative , or both methodologies. Qualitative methodologies were considered in articles that used one or more of the following tools: interviews, surveys, case studies, literature review, inventories, or descriptive studies of environmental degradation. Quantitative studies were defined as articles that develop scenario constructions to measure the current or projected impacts of the policies studied. In this latter case, pollutant levels and emission estimates were measured to determine their respective health effects. Quantitative studies largely required the use of modeling and statistical analysis, co-benefit analysis, life cycle assessment, and risk assessment. Quantitative and qualitative methodologies both use case studies but differ in their outcomes. A tendency from the selected articles was that qualitative studies tend to be used for policy support as opposed to quantitative studies that are more utilized to evaluate an existing policy.

What policy approaches are more associated with qualitative or quantitative methodologies? As shown in Fig.  4 , the largest number of articles (nine) used quantitative methods and addressed a regulatory policy that primarily included technology, fuels, and circulation-restriction initiatives. Approaches combining qualitative and quantitative methods represented the second highest number of articles (six). In this case, alternative approaches to mitigating air pollution were studied, although the focus remained but on technology and fuels. In this category, alternative initiatives represented an important component of the research. This is evident in the number of articles evaluating alternative initiatives that used exclusively qualitative methodology and looked at other air management policy types. Few studies (two) used qualitative methodology to look at regulatory and economic initiatives, and both looked at policies that had a circulation-restriction motivation.

An external file that holds a picture, illustration, etc.
Object name is 11524_2015_7_Fig4_HTML.jpg

Air pollution policy management. QUAL qualitative, QUANT quantitative, REG regulatory approach, ECO economic incentives, OTH other.

Data Interpretation

In terms of outcomes, articles that provided support to policy development usually delivered expected results and recommendations, as described in Table ​ Table1. 1 . In the case of Lagos, Nigeria, for example, the study offers an overview of the environmental degradation taking place and prioritizes local needs, while calling for measures to increase awareness and urging for policy intervention. 53 This article points out the risks of air pollution due to vehicular emission, waste burning, and industries, emphasizing the need for mitigation and adaptation measures. Importantly, this article brings in a social dimension as an essential and complementary tool for a successful policy via educational programs. Such social dimensions are also seen in a study in New Delhi, India, where improvements to air quality are linked not only to PM 10 reductions—also found to reduce CO 2 —but to greater health benefits for the poor. 40 Garg goes one step further, suggesting that since poor people are the first victims of air pollution, higher-income populations should take on the burden of the cost associated with air pollution as a way to promote health equity. Questions of responsibility are also emphasized in the cities of Bogotá, Colombia, Curitiba, Brazil, and Santiago, Chile, where transport can exacerbate inequalities. Indeed, a suggested way to cope with it would be for policy makers to incorporate health aspects into their agenda, particularly when addressing public transportation interventions. 45

Garg, Becerra et al., and Wright and Fulton also highlight more efficient policies using an exploratory description of different challenges and initiatives based on a cross-study of cities, recommending the most beneficial measures. They identify mode shifting (referring here as the change in the type of way people use to get around) as the most cost-effective means of reducing GHG emissions. 22 Furthermore, restrictions on cars, integrated public transportation, rapid transit, and bike lanes appear to be efficient ways to promote and encourage active transportation. Active transportation and multi-modal modes of transport are mentioned in several studies as the best way to lower vehicle emissions, while also increasing physical activity and improving health, 43 , 45 , 54 by encouraging walking or the use of bicycles, as suggested in studies based in Auckland, New Zealand, London, UK, and New Delhi, India.

Another recurrent recommendation is to improve road conditions. In Auckland, New Zealand, the improvement of road conditions showed positive results in lowering emissions and encouraging more active transportation mobility, as measured by estimates in the reduction of travel time. The authors calculated what the effects on health would be if short car trips were substituted by cycling (about 5 % of trips) and found that such a change could reduce the number of injuries due to traffic accidents and lower the effects of vehicular emissions. 55 In Durban, South Africa, in addition to technology, road improvement interventions appeared to reduce time of travel and the efficiency of road freight transport by lowering GHG emissions. 56 Moreover, in Latin American cities, Becerra et al. urge for a greater inclusion of health considerations in transport policy design and point out that the number of cars is still increasing in the cities studied.

Articles that provide policy support and development tend to focus on identifying how to improve public transport networks in the city, prioritize its use by locals, and discourage the use of privately owned vehicles. The bus transit system in Bogotá, Colombia is cited twice as an example of an efficiently integrated system 23 , 45 that encourages use and significantly reduces CO 2 emissions. The idea of promoting transport policies is raised for New Delhi, where clean development mechanisms (CDM) and integrated policies are seen as having the greatest co-benefits. 39 However, data collection in Delhi is seen as a challenge for improving public transportation. In Durban, the lack of data is cited as a challenge to policy development. Aiming to overcome this challenge, tests were conducted using passive samplers, which were proven to be effective and affordable for pollution monitoring in most surrounding municipalities, 57 offering a low-cost potential solution for bridging the data gap and improving technology.

Lowering emissions is one of the major means of improving local air quality, in addition to being the most frequent approach to coping with vehicular pollution. This is being done in three main ways: technology and fuel improvement (electric vehicles, biofuels, and natural gas); restriction policies such as emission standards, mandatory vehicle inspections, and improvement of road conditions; and limitations on allowable travel distances, as in Durban and Auckland. Emission inventories seemed to be a departure point, as in Kathmandu, Nepal, where it was possible to construct different scenarios applying EURO emission standards. 58 The results were rather promising and supported the thesis that prioritizing vehicular policies could have an impact on both local air pollution and climate change. Indeed, if Kathmandu were to apply EURO III standards, in 20 years, toxic air pollutants would decrease by 44 % and climate-forcers by 31 %. 58 In London, a 2004 study also recognized the importance of strict emission standards and vehicle technology improvements, prior to t he implementation of vehicle congestion charge. The authors found that although emission standards were an important tool for reducing emissions, technology, in particular those that foster alternative fuels, was most successful at improving local air quality and reducing climate change by 2020. 52 In Delhi and Mumbai, India, energy efficiency was tested on vehicles using natural gas technology (compressed natural gas (CNG)), four-stroke wheelers, and battery-operated vehicles (BOV) for GHG and local air pollutant mitigation strategies. 44 Results demonstrated an important contribution to CO 2 mitigation among local air pollutants but noted challenges associated with the use of natural gas as a fuel, demonstrating the difficulties in finding the optimal vehicle mix to improve air quality and mitigate climate change.

Indeed, as seen in the Indian cities studied, lowering emissions in the policy development stage requires looking for and testing for the most efficient technologies for vehicles. In Toronto, Canada, fuel cell/plug-in hybrid electric vehicles (FCPHEVs) were found to achieve greater outcomes to pollutant reductions. 59 However, all of the tested alternative vehicle technologies, including hybrid electric vehicles (PHEVs), fuel cell vehicles (FCVs), and fuel cell/plug-in hybrid electric vehicles, had in common to be impact precursors of photochemical smog. 59 Interestingly, a study on the potential of electric vehicles in Dublin, Ireland showed that such technologies are beneficial for reducing traffic-related pollutants, but that the time required to change part of the taxi fleet could offset these benefits for climate change and air quality. 60 In London, five technologies were tested for their impact on PM 2.5 levels and percentage of population exposed, the most efficient being LB-CNG buses.

The choice of fuels is indeed an important tool for policy makers at the local level but also has been considered for contributing to global CO 2 target reductions. On the other hand, the London example showed that emission standards are essential for coping with local air pollution, but their health benefits can be reduced if they are not combined with vehicle technology improvements and alternative means of transportation. 43 , 52

On a different level, post-policy studies offered the opportunity to emphasize beneficial and non-beneficial interventions by measuring their results and highlighting primary findings. As expected, a common concern in lowering emissions is the choice of fuels and technology. Out of 15 articles, five evaluated the use of CNG for vehicles to calculate their environmental impact and determine the best available “ecological alternatives,” e.g., CNG, liquefied petroleum gas (LPG), or a hybrid. 61 For instance, in Madrid, Spain, a life cycle analysis of the introduction of “ecological alternative fuels” on a diesel taxi fleet concluded that this choice of fuels had a positive environmental impact overall but not at the manufacturing stage. Indeed, another major contributor to the effects of fuels was related to vehicle speed rather than choice of fuel. 61 In Chinese cities, CNG was found to be a better option for buses, while diesel was better for taxis. 47 , 62 A study carried out in New Delhi correlated the 2002 switch to CNG fueling with an increase in CO 2 and CH 4, 42 but also with a reduction in black carbon (BC), an important pollutant for GHG reduction. A similar result was found in Dhaka, Bangladesh, where CNG helped reduce local air pollution but had little effect towards climate change mitigation. 63 In UK cities, a study found that CO 2 policies led to diesel growth and higher emissions of particulate matter but cautioned that there was a need for further research to understand such impacts. 64 In addition, post-policy articles combined studies that were mostly located in Asia, with the exception of two European, London and Madrid, and two Latin American cities, Bogotá and Mexico.

Moreover, with regard to the transport sector, the most efficient policies were those that had developed and integrated into their strategy approaches that considered CDM to target emission reductions. There is an emphasis on encouraging more co-benefit analysis as a way to improve transport policy overall, 38 , 41 , 49 , 65 including land use and transport planning. In Shenyang, China, results showed the necessity to include bus fleet renovation in transport policies, green vehicle purchase, and improved infrastructure to maximize benefits. In a cross-city study, Labriet concluded that CDM was not only beneficial to GHG and air pollution mitigation but went one step further by identifying it as a tool to measure accountability and policy sustainability. 65

Other articles evaluated restriction policies, particularly in measuring the impacts of current emission standards. In Beijing, studies found that current emission standards had little effect on reducing NO x , demonstrating the lack of efficient control technologies and compliance to programs as a limitation to the success of these standards, 47 and calling for better-quality fuels and multi-pollutant reduction strategy. According to Wang, the benefits of emission standards were also offset by the number of trucks circulating around Beijing 48 that constituted a high source of BC and PM 2.5 , suggesting that measures that focus only on standards and improving engines are not sufficient. However, in Bangkok, Thailand, the Inspection Maintenance Program for vehicles was a successful restriction policy, 66 where health benefits were greater than the costs of implementation. Another measure with positive effects was road charges, which lowered congestion. In London, the anti-congestion charging scheme was an important tool to lower NO x and PM 10 and enabled the government to reach its pollution reduction and climate change targets. 67 Creutzig also found benefits from road charges imposed in Beijing and highlighted the importance of developing policies that look at the supply and demand aspects of these initiatives. 46 Traffic control in Beijing was essential during the Olympics in helping the city meet its global target of CO 2 emission reduction 3 and also encouraged the use of satellite-based technology for collecting data. During the Olympics, satellites were very helpful in identifying reductions and increases in pollutant levels.

The contribution of vehicles to air quality and climate change mitigation has been demonstrated by academic studies, in particular in the transport sector. However, there is potential for further research, in particular to identify the most beneficial policies that point to the right fuel and right technology for lowering emissions. In addition, few articles address the issue of privately owned vehicles, but those that do implicitly note that implemented polices are offset by the growing number of privately owned vehicles. Furthermore, replacement of the old vehicle fleet constitutes another important element to be incorporated into policymaking, most notably in cities of the developed world. Interestingly, urban policies tend to incorporate outcomes not only for air quality but also for climate change mitigation. The reviewed articles reflect the many challenges to developing and implementing policies that with a positive impact on both air quality and climate change mitigation. However, in the pre-policy table, efforts seem to be concentrated on offering other approaches while focusing on fuels and technology (C). Indeed, in the pre-policy stage, few articles support the circulation-restriction initiatives (A) while acknowledging that the speed of vehicles is one of the main components in reducing emissions.

In the post-policy section, policy approaches are evenly distributed between restriction of circulation initiatives and fuels and technology. Future studies should be encouraged to evaluate the benefits of alternative initiatives in urban centers as opposed to focusing on emissions. Studies have demonstrated that multi-modal modes of transportation have the greatest benefit, as does the integration of clean development mechanisms. As seen in Madrid, Spain, it is essential to look at the effects of a policy from its early stages to evaluate its full impact. CNG as a fuel, for example, showed mixed results as an offsetting of climate change mitigation strategies but, combined with the implementation of “ecological fuels,” was shown to be an important way to reduce emissions. Initiatives such as the maintenance program in Bangkok, Thailand or the congestion charge program in London have had overall positive impacts, in particular in terms of health. Reduced vehicle emissions can also be an ally to climate change mitigation: the study on the effects of the restricted circulation of vehicles during the Beijing Olympic games proved how the absence of vehicles managed to lower CO 2 emissions.

In Tables  1 and ​ and2 2 (pre- and post-policies), only three articles addressed equity and the basis of the right to clean air. As the issue of “clean air for all as a human right” gains traction, 40 , 68 – 70 it will be crucial to integrate a social dimension to local air quality and climate change mitigation policies. In Indian cities, Li and Garg call for the importance of strong policy instruments that include concepts of social welfare, quality of life, and equity. 40 , 41 O’Neill et al. have stressed the importance of applying the social determinants of health to measure and reduce health disparities, 71 , 72 strengthening Becerra’s suggestion to expand the inclusion of health into the transport policy agenda. This issue raises the question of scale, a limitation found in this study. Indeed, the chosen focus on the level of the city might have resulted in missing potentially important nationwide policies with an impact on air quality and on climate change.

Urban planning and governance are also important factors in developing successful policies. For instance, urban planning has been discussed as a crucial issue and an important potential solution for improving transport infrastructure. Urban governance was also reported as a challenge for efficient policymaking in Indian and Chinese cities. As urban environmental problems are increasingly linked at the global level, challenges concerning governance reinforce the problem of responsibility 73 : who will bear the burden of reinforcing and monitoring these policies? Although beyond the scope of the present study, the purpose of such issues is fundamental to the well functioning of air policies. As cities become experimental hubs of climate change initiatives, 7 challenges also arise as to how this knowledge will be disseminated and how to improve data access. In this sense, academics have an important role to play.

This study has addressed the importance of incorporating air pollution measurement while developing climate change control experiments in cities. It highlighted what kinds of policies are being developed around the world and what kinds of primary outcomes have been documented. While each city must be understood in its particular social and economic timeframe, and we recognize that certain policies implemented in one place might not be the most suitable elsewhere, understanding which energy choices have been made for mobile sources of air pollution in certain cities can be critical in showing that addressing air pollution is an ally of climate change mitigation, reducing local air pollution does not harm climate change mitigation, and ignoring climate change mitigation pollutants can harm local air quality. 2 , 20 , 40

Local air pollution and global climate change policies should work together to maximize the benefits of lowering pollution levels and mitigating climate change. Cross-city studies are fundamental, and there is a gap in scholarship studying southern-hemisphere cities. 74 Given the lack of available data in certain parts of the world, studying the efficacy of successful air pollution policies implemented elsewhere should be seen as an important tool for better comprehending successful initiatives and their benefits. Ostrom believed that local initiatives are indeed the ones that have a greater global impact. 75 In this study, the local examples highlighted show a growing concern of cities to fight air pollution and tackle climate change at the local level.

This review demonstrates that local air pollution policies are not only beneficial to cities but also important for mitigating and adapting to global climate change. In addition, we see a need to further study policies that address private vehicle emissions and the correlation between traffic patterns and air pollution. This study suggests that more in-depth cross-city studies have the potential to highlight best practices, in both local and global terms. Finally, this research calls for the inclusion of a more human rights-based approach, which aims to insure the right to “clean air for all people” and to reduce factors that exacerbate climate change.

Breeze Technologies

10 things you can do to improve air quality in your city

how to improve air quality in city

Air pollution is an environmental issue that affects everyone. Here’s how you can do your part in clearing the air.

Use public transportation

Public buses, trams, subways, and trains are not only more affordable than driving your own car, they also help cut congestion and reduce air pollution. Oftentimes, there are discounts for children, students, seniors, and weekly/monthly/yearly passes. Rather than having to use a ticket machine or a counter, many cities now provide the option of getting e-tickets through their app. Check the website of your local public transport service for the  details!

Walk and cycle more

Aside from the fact that walking and cycling produce zero emissions, these actions are also good for your health, so you can get a workout out of travelling! Don’t have a bike? Rent one! Services like Call a Bike (Germany) and BimBimBikes (worldwide) connect individuals with bike rental platforms so that you can procure one with ease.

Carpool or ride-share

Know someone who regularly drives to the same locations as you do? Travelling together in a single vehicle can reduce emissions, fuel costs, and traffic congestion. Don’t have anyone to carpool with? You could find a group on Facebook , or apps such as Waze Carpool (Brazil, Israel, Mexico, U.S.) and BlaBlaCar (Europe) allow you to commute with people on their daily routes as well as on road trips between cities!

Use an electric vehicle

If you really need to drive your own vehicle, consider investing in an electric car. There are options to be found in all major brands on the market today. Electric cars are more cost-effective in the long run due to lower maintenance fees, tax incentives, and low electricity costs when compared to traditional petrol or diesel cars. Other pros include zero emissions, quiet driving, and fast and convenient home charging. If going fully electric doesn’t sound appealing, try a hybrid car. These vehicles combine a diesel or petrol engine with an electric one motor, allowing you to use both options or switch between them while on the road. Hybrid vehicles consume less fuel and produce less emissions than a regular car. 

Buy local products and produce

Shopping local means that the food had to travel less to where you are, thus decreasing transport emissions. Aside from the environmental benefits, you gain control over what you eat by knowing where the food comes from and how it was produced. You can also feel good about supporting local businesses! Products made close to home are usually highlighted on the packaging at your local supermarket. You are also able to find them by connecting with your community at your resident farmer’s market!

Join urban gardening initiatives

Urban gardening initiatives come in a variety of forms – backyard beekeeping, vertical and rooftop gardening, local farms – but what ties them together is the community. Benefits of joining one include positive social interaction, increased food security, efficient utilization of space, and access to fresher, healthier food. Carbon emissions are reduced from the plants you’re growing themselves and from the fact that the food didn’t have to travel to where you are! 

Adopt green roofs for your house or your factory

A green roof is a vegetative layer grown on rooftops. They purify the air, serve as a habitat for local animals, reduce ambient noise from outside, slow stormwater runoff, provide insulation in the winter and protect the house from heat in the summer. While all green roofs function similarly, the actual installation will depend on the region, climate, building, type, and design.

Those with a lot more space to offer could alternatively install solar panels on their roofs. These will not only power your buildings with clean, renewable energy, but you could even sell the excess power produced back into the grid!

Switch to a renewable energy plan

Changing energy suppliers for your house means that the power you use in your daily life will be changed from coal, oil, and natural gas to that of sun, wind, and water. Not only will you reduce your carbon footprint by doing so, but renewable energy is usually cheaper! Save the environment and your wallet by looking for clean energy companies near you today!

Write to your city government to ask about air quality data and clean air actions

Air quality data is usually handled by a department of your city’s, state’s or country’s environmental agency. You can find our about the local air quality levels of your neighborhood by going to your regional or federal government website. Ideally, you will get information on how the measurements are gathered, current policies on curbing air pollution, trends in air quality, and much more. However, air quality data is traditionally gathered only at a few limited locations . This means that the location of the next monitoring station with available data is most likely far away from the places that matter most to you.  

By writing to your local environmental agency, you may be able to receive modelled data applicable directly to the locations of your interest – for instance, where you live, where you work or where your children go to school. If they are not able to provide this information, you can also write to the politicians representing your neighborhood or in your city council. Every inquiry is important and will register as rising citizen interest in the topic of air quality. If more citizens show an active interest in data about air quality and clean air actions, city officials are more likely to take action by increasing the number of measurement locations and by proposing legislation to curb emissions.

There are also various initiatives targeting air pollution that require the assistance of citizens . You can find these on portals like the Urban Innovative Actions (Europe), or you can write to your government office for clean air actions that you can take part in.

Become an air quality sensor host

By volunteering to install an air quality sensor on your own premises , you help provide comprehensive air quality information for governments and fellow citizens in making decisions on improving the air we breathe. There are no costs incurred for becoming a sensor host aside from the sensors’ very low power consumption. The gathered air quality data will be publicly available on our citizen portal . Join us in helping clear the air today!

  • Indoor Coronavirus prevention
  • Urban Air Quality
  • Industrial Immissions
  • Air Quality Sensors
  • Wildfire Detection
  • Clean Air Actions
  • Air Quality Academy
  • Press & Media
  • Privacy Policy
  • Investor Relations

UN Sustainable Development Goals Poster

U.S. flag

An official website of the United States government

Here’s how you know

Official websites use .gov A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS A lock ( Lock A locked padlock ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

JavaScript appears to be disabled on this computer. Please click here to see any active alerts .

Salt Lake City, Utah Adapts to Improve Air Quality Through Smart Growth

Green Bike

In 2014, Salt Lake City was designated a Climate Action Champion Community for their leadership in reducing emissions and increasing climate resilience and adaptation to air quality concerns from climate change. The Sustainable Salt Lake Plan 2015 articulates the city’s broad and ambitious agenda to protect its resources, enhance its assets, and establish a path towards greater community resiliency. The plan set goals to improve air quality, protect community health, and reduce particulate matter (PM) and ozone pollution (which are both projected to be exacerbated by climate change). The city adopted specific transportation measures to decrease miles traveled, reduce vehicle idling, and promote alternatives. These clean air strategies reduce current air pollution (mitigation) that is expected to be exacerbated by climate change (adaptation).

While continuing to address air quality issues, Salt Lake City is now formulating a vulnerability assessment and adaptation plan. The Salt Lake City Climate Response Plan is expected to include: a climate vulnerability assessment, a greenhouse gas mitigation plan, and an adaptation plan. This comprehensive approach to climate adaptation builds off of previous adaptation efforts to better help the city anticipate, plan and prepare to take action to protect residents from future public health and air quality concerns.

  • Sustainable Salt Lake Plan 2015 (PDF) (30 pp, 23 MB, About PDF ) 

Similar Cases and More Information

To read more about Salt Lake City's efforts to reduce transportation related air emissions, see the EPA's Sustainable Transportation for a Sustainable Future Page. Salt Lake City implemented air quality actions which also provided mutual benefits as climate mitigation activities. For an example of other strategy that can provide co-benefits, see how Chicago used Green Infrastructure to Reduce Extreme Heat. If you would like to know more information about how climate change will affect Air Quality and Human Health view the ARC Homepage.

  • U.S. EPA - Transportation, Air Pollution, and Climate Change
  • See how Chicago used Green Infrastructure to Reduce Extreme Heat
  • See how Central New Mexico is working to improve air quality by accounting for future climate change in the city’s transportation plans and ongoing projects

Submit a Case Study

  • Air & Climate
  • Climate Adaptation
  • Sustainable Salt Lake Plan 2015 (PDF) (30 pp, 23 MB)
  • Climate Action Champions
  • Sustainable Transportation Case Study: Salt Lake City, Utah (PDF) (2 pp, 46 K)
  • Climate Change Adaptation Resource Center (ARC-X) Home
  • Your Climate Adaptation Search
  • Implications of Climate Change
  • Adaptation Planning
  • Adaptation Strategies
  • Case Studies
  • Federal Funding & Technical Assistance
  • Underlying Science
  • EPA Contacts & State Websites
  • Skip to main content
  • Keyboard shortcuts for audio player

EPA rule that limits pollution is being challenged in the Supreme Court

Carrie Johnson 2016 square

Carrie Johnson

A key environmental effort to improve air quality and protect people from downwind pollution faces a legal challenge at the U.S. Supreme Court from several states and energy companies .

  • Pre-Markets
  • U.S. Markets
  • Cryptocurrency
  • Futures & Commodities
  • Funds & ETFs
  • Health & Science
  • Real Estate
  • Transportation
  • Industrials

Small Business

Personal Finance

  • Financial Advisors
  • Options Action
  • Buffett Archive
  • Trader Talk
  • Cybersecurity
  • Social Media
  • CNBC Disruptor 50
  • White House
  • Equity and Opportunity
  • Business Day Shows
  • Entertainment Shows
  • Full Episodes
  • Latest Video
  • CEO Interviews
  • CNBC Documentaries
  • CNBC Podcasts
  • Digital Originals
  • Live TV Schedule
  • Trust Portfolio
  • Trade Alerts
  • Meeting Videos
  • Homestretch
  • Jim's Columns
  • Stock Screener
  • Market Forecast
  • Options Investing
  • Chart Investing

Credit Cards

Credit Monitoring

Help for Low Credit Scores

All Credit Cards

Find the Credit Card for You

Best Credit Cards

Best Rewards Credit Cards

Best Travel Credit Cards

Best 0% APR Credit Cards

Best Balance Transfer Credit Cards

Best Cash Back Credit Cards

Best Credit Card Welcome Bonuses

Best Credit Cards to Build Credit

Find the Best Personal Loan for You

Best Personal Loans

Best Debt Consolidation Loans

Best Loans to Refinance Credit Card Debt

Best Loans with Fast Funding

Best Small Personal Loans

Best Large Personal Loans

Best Personal Loans to Apply Online

Best Student Loan Refinance

All Banking

Find the Savings Account for You

Best High Yield Savings Accounts

Best Big Bank Savings Accounts

Best Big Bank Checking Accounts

Best No Fee Checking Accounts

No Overdraft Fee Checking Accounts

Best Checking Account Bonuses

Best Money Market Accounts

Best Credit Unions

All Mortgages

Best Mortgages

Best Mortgages for Small Down Payment

Best Mortgages for No Down Payment

Best Mortgages with No Origination Fee

Best Mortgages for Average Credit Score

Adjustable Rate Mortgages

Affording a Mortgage

All Insurance

Best Life Insurance

Best Homeowners Insurance

Best Renters Insurance

Best Car Insurance

Travel Insurance

All Credit Monitoring

Best Credit Monitoring Services

Best Identity Theft Protection

How to Boost Your Credit Score

Credit Repair Services

All Personal Finance

Best Budgeting Apps

Best Expense Tracker Apps

Best Money Transfer Apps

Best Resale Apps and Sites

Buy Now Pay Later (BNPL) Apps

Best Debt Relief

All Small Business

Best Small Business Savings Accounts

Best Small Business Checking Accounts

Best Credit Cards for Small Business

Best Small Business Loans

Best Tax Software for Small Business

Filing For Free

Best Tax Software

Best Tax Software for Small Businesses

Tax Refunds

Tax Brackets

Tax By State

Tax Payment Plans

All Help for Low Credit Scores

Best Credit Cards for Bad Credit

Best Personal Loans for Bad Credit

Best Debt Consolidation Loans for Bad Credit

Personal Loans if You Don't Have Credit

Best Credit Cards for Building Credit

Personal Loans for 580 Credit Score or Lower

Personal Loans for 670 Credit Score or Lower

Best Mortgages for Bad Credit

Best Hardship Loans

All Investing

Best IRA Accounts

Best Roth IRA Accounts

Best Investing Apps

Best Free Stock Trading Platforms

Best Robo-Advisors

Index Funds

Mutual Funds

People are moving out of cities with poor air quality — but many end up facing other climate risks

thumbnail

  • About 1.2 million more homeowners and renters moved out of than moved into U.S. cities with high risk of poor air quality between 2021 and 2022, according to a new analysis by Redfin.
  • While residents are moving to areas that are affordable and have low air quality risks, such places are exposed to different hazards.

While both renters and homeowners are beginning to take climate hazards into consideration, affordability continues to drive moving trends .

Between 2021 and 2022, about 1.2 million more homeowners and renters moved out of than moved into U.S. cities with high risk of poor air quality, according to a new analysis by Redfin, a real estate firm. Metros with low risks of poor air quality saw one million more newcomers in the same timeframe.

"At an individual level, we know that people respond to climate risks and it impacts the decision of exactly what home to buy," said Daryl Fairweather, chief economist of Redfin.

Researchers at Redfin analyzed domestic migration data from the U.S. Census Bureau and air quality risk scores from First Street Foundation, a nonprofit climate research organization based in New York.

More from Personal Finance: How more supply is helping rent prices cool More than 18 million rental units at risk from climate hazards Renters are most exposed to climate hazards in these two states

First Street Foundation labels a metro as "high risk" when at least 10% of properties fall into the major, severe or extreme categories. A "low risk" metro is where less than 10% of properties fall into those categories.

The rating system is based on the number of poor air quality days expected within the next 30 years and it includes two common pollutants: particulate matter, which often comes from wildfire smoke, and ozone, which is when pollutants react with heat or light.

Air quality and affordability are pushing residents out of 13 metros areas, many on the West Coast. Most of the inbound moves are heading into Sunbelt states such as Arizona, Florida, Nevada, North Carolina, South Carolina, Texas and Tennessee. Yet, movers will confront different climate hazards in those areas, said Fairweather.

Much of the Sunbelt "has [a] low air-quality risk but it has high heat risk, high flood risk, high wind risk from things like hurricanes," she said.

'We're already starting to see some shifts'

People are responding to the danger of climate-related risks, Jeremy Porter, head of climate implications research for First Street Foundation, previously told CNBC. 

"We're already starting to see some shifts in population where people, as they can, they're moving away from risk and the people that can't afford to move away from risk are stuck in those risky areas," said Porter.

When looking at moving trends within counties and cities between 2000 and 2020 paired with flood risks, researchers at First Street Foundation noticed clear signals of people moving away from areas exposed to flooding.

The hidden reason some U.S. homes are losing value

In total, there are more than 2.9 million census blocks or neighborhoods in the U.S. that have levels of flood risk that are above the "tipping point," or when flood risks begin to outweigh the area's benefits, such as job markets or proximity to the coast.

Nearly 818,000 neighborhoods in the U.S. experienced a population decline of more than nine million people between 2000 and 2020, First Street Foundation found. Additionally, more than 3.2 million, or 35.5%, of those residents said they left specifically because of the flood risk.

'I personally was impacted by air quality'

More than 85% of homes in 13 major cities are highly exposed to poor air quality. Nine are in California and the rest are spread out in Washington, Oregon and Idaho, Redfin found.

"I personally was impacted by air quality," Fairweather said. She and her family used to live in Seattle before the Covid-19 pandemic.

But in September 2020, a major smoke event in the city due to wildfires motivated her to relocate her family to Wisconsin. While the smoke lasted two weeks in Seattle, Fairweather and her family decided not to move back.

"Climate change is definitely a factor and it was like the straw that broke the camel's back," she said. But as with many people, it wasn't the only reason they decided to relocate.

On top of the poor air quality, many residents are leaving these areas because they're being priced out. Home prices in riskier metros are 65% higher than prices in low-risk metros, according to Redfin.

Affordability remains a priority for movers

About 83% of would-be homebuyers considered at least one climate risk when shopping for a home, Zillow Group, a real estate site, found in September.

Yet, some places continue to grow in population despite the underlying hazards. "Risky growth areas" are places with high levels of flood risk but continue to see population growth. Such places saw a population increase of about 17.6 million, or 30% of the country's population, according to First Street research.

As housing costs linger at record highs, factors such as affordability and employment opportunities remain as top priorities for buyers and renters alike, said Fairweather.

"It's going to become more and more important every year. I think people will increasingly seek out information about climate risks when buying a home," she said.

If not already, insurance costs will likely be a way many people first reckon with climate risk, said Fairweather.

Insurance bills could go up if a resident is based in a place that is exposed to increasingly common risks, and in some markets, insurers are pulling back on coverage .

"That is already happening in California, Texas and Florida. It could impact even more places," she said.

Did you move recently because of a recurring climate hazard or weather risk? Email me at [email protected] . Don't miss these stories from CNBC PRO:

  • Three stocks that could replace Tesla in the 'Magnificent 7'
  • Morgan Stanley hikes Nvidia price target ahead of earnings: 'AI demand continues to surge'
  • Vanguard launches two new ETFs to hit this sweet spot of tax-free fixed income
  • Berkshire Hathaway topped $600,000 a share last week, aiming at $1 trillion market value

comscore

5 ways to improve your Utah home's winter air quality

By utahradon.org | posted - feb. 20, 2024 at 7:00 p.m., (istock/getty images).

Estimated read time: 4-5 minutes

Utah's winter outdoor air quality is often worse than major metropolitan cities like Los Angeles and New York City, and poor air quality can reduce Utahn's life expectancy by up to 3.6 years, according to a study that included researchers from BYU, University of Utah, Utah State University, Yale and the University of Colorado. Experts attribute 2,500 and 8,000 premature deaths in Utah to air quality issues.

Air quality also puts a strain on the broader economy. An article published in MDPI reported the economic cost of air pollution can total upwards of $3 billion annually.

While Utah's outdoor air quality receives a lot of attention, health experts say it's just as important to pay attention to indoor air quality. According to the American Lung Association, Indoor air can be up to five times more polluted than outdoor air and many Americans spend 90% of their time indoors.

–American Lung Association

This winter, Utahns are advised to improve the air quality inside their homes by:

Replacing the furnace air filter

Air filters can last up to 6–12 months, but some need replacing sooner. HVAC professionals suggest Utahns check their air filters monthly and replace them as soon as they look dirty or full. Depending on how many people are in a home and how large the home is, replacing the filter more or less frequently may be necessary to maintain good air quality.

It's important to remember not all air filters are created equal. Air filters are ranked on a Minimum Efficiency Reporting Value (MERV) scale from 1–12, with 12 filtering the most particulates.

A lower MERV filter might be a good fit if base particulates like pollen or dust mites are the only concern. However, if the home is exposed to tobacco smoke, is in an area with high outdoor pollution (like the Salt Lake Valley in the winter), or is at risk for mold spores, a filter on the higher end of the scale may be advisable. Normal furnace filters don't impact gaseous pollutants in homes.

Testing for radon

Radon is the leading cause of lung cancer among non-smokers, and Utah has four times more radon than the national average. In fact, 1 in 3 homes in Utah has dangerous radon levels (compared to 1 in 15 homes nationally). Because Utah homes are shut during the winter months and because snow and cold temperatures reduce the amount of radon that can escape outdoors, the concentration of radon inside a home can increase significantly during cold months.

This is an important issue for homes with families in particular. According to Nick Torres, an advocacy director of the American Lung Association , households with children should be extra wary as kids are more susceptible to radon.

The only way to detect radon is to test for it. Currently, all Utahns can get a free radon test at UtahRadon.org , and normally, tests can be purchased from the State.

Even if a home has been tested before, the Environmental Protection Agency (EPA) recommends testing every two years for radon.

Running an air purifier

Plenty of things can impact the air quality inside a home, including pollution, dust, dander, and other "particulate matter," which refers to the solid and liquid particles in the air we breathe in that are far too small for the eye to see. Air purifiers help reduce the particulate matter load, thus reducing the likelihood of developing lung diseases, and some can also curb the spread of airborne viruses and bacteria.

A good quality air purifier can help keep all these irritants at bay. Purifiers have a limited range, so homeowners may need more than one in a home. Purifiers do not help with gas-based contaminants like radon and carbon monoxide.

Checking carbon monoxide detectors

Just like radon, carbon monoxide can't be detected with human senses, so it's crucial to have carbon monoxide detectors inside all homes. Like smoke detectors, these should be checked and cleaned regularly, and batteries should be replaced annually.

Carbon monoxide poisoning may start with flu-like symptoms and can eventually cause brain damage, so it's important to maintain CO detectors to prevent exposure from being misdiagnosed as a seasonal illness. The EPA recommends placing one detector on every floor. These detectors generally cannot detect other harmful indoor gasses, like radon.

Increasing ventilation to avoid mold

Mold grows in humid, damp environments, and if mold grows in a home, it can cause many health issues. Many Utahns ignore the potential of mold growth because we live in such a dry environment, but it's still a major concern in Utah .

Mold can start growing in a home in as little as 24 hours. To avoid mold growth, increase ventilation in bathrooms and laundry rooms using small fans. If moisture increases noticeably inside a home, use a dehumidifier to trap the humidity and return areas of a home to a healthy moisture level.

All of these measures can be understood as short-term solutions with long-term impacts. Testing for Radon is a short-term activity with potentially long-term implications — that's the arc of outdoor and indoor air quality in Utah. The longer-term health impacts are best mitigated by regular, proactive actions by individual Utahns.

Related topics

More stories you may be interested in.

how to improve air quality in city

How will the IRS spend its extra money? Rep. Blake Moore asks during House committee hearing

how to improve air quality in city

University of Utah highlights positive impacts of equity, diversity and inclusion programs

how to improve air quality in city

Utah business leaders, homelessness officials urge lawmakers to approve $193M budget request

Most viewed.

  • Pet Gila monster bites Colorado man, who dies in what experts call a 'rare event'
  • 2 adults are charged with murder in the deadly shooting at Kansas City's Super Bowl celebration
  • Warning, advisories issued as another atmospheric river arrives in Utah
  • Former Davis High secretary pleads guilty to using school funds for herself
  • Patrick Kinahan: All-Star game continues to stain NBA
  • Supreme Court rejects appeal from 3 GOP House members over $500 mask fines
  • Police: 9-year-old Tooele child arrested after shooting, killing family member
  • Boy dies after gasoline poured on fire explodes in Davis County
  • Church of Jesus Christ announces name change for Provo temple
  • Franke, Hildebrandt to spend years, maybe decades in prison for 'concentration camp-like' abuse

STAY IN THE KNOW

how to improve air quality in city

KSL Weather Forecast

how to improve air quality in city

  • Architecture + Design
  • Real Estate
  • AD it Yourself
  • Condé Nast Store
  • The Magazine

Explore Architectural Digest across the globe

Select international site

  • España
  • México
  • Middle East

AD Logo

How to Perform an Air Quality Test at Home

By Amanda Lutz Updated February 15, 2024

Understanding Indoor Air Quality

  • Signs of Bad Air
  • How to Test

Best Air Quality Monitors

  • How to Improve

Our Recommendation

Indoor air quality (IAQ) is incredibly important, especially at home, where many people spend 62% of their waking time . Breathing airborne toxins such as mold spores, allergens, and combustion byproducts that linger indoors can compromise your health. Homeowners can manage potential hazards and stay healthy by regularly conducting IAQ tests and taking action accordingly. Read on for more information on what causes poor air quality, how to test air quality, and how to improve air quality.

IAQ is an objective measure of the quality and purity of the air within an indoor structure such as your home or one of its rooms. The IAQ of your office may differ from that of a bathroom with no windows, for example.

IAQ is measured against an IAQ index , which considers the types of hazards present in the air and the efficacy of current mitigation strategies. Higher scores translate to higher concentrations of hazards and fewer mitigating features in the air, and the opposite is true of low scores.

Some of the pollutants or hazards that could affect your home’s IAQ include the following:

  • Carbon monoxide, tobacco smoke, incense particulate, and other combustion byproducts
  • Lead or asbestos, which are more common in older homes
  • Mold and mildew
  • Ozone and volatile organic compounds (VOCs)

Environmental factors can change the degree to which those contaminants affect air quality. Regularly leaving the windows open to get fresh air and having an air filtration system can help. Conversely, stagnant airflow and poor ventilation can make contaminants more severe.

Signs of Poor Indoor Air Quality

The presence of contaminants and hazards may be a sign that your home has poor air quality. There are other indicators too, so look out for these common signs of regular exposure to air quality issues:

Health Problems

Poor IAQ is dangerous because it can have negative health effects on individuals. Call a professional to check out your home’s air quality if anyone in your household regularly experiences the following symptoms:

  • Allergic reactions
  • Eye irritation
  • Frequent coughing
  • Irritation in throat or lungs
  • Shortness of breath

Respiratory symptoms, or increased respiratory irritations, can be products of smoke, mold, pet dander, pollen, and chemicals such as formaldehyde.

Humidity itself isn’t a sign of poor air quality, but it could be a contributing factor. Humid air encourages the growth of mold, mildew, and rot. Heavy, humid air can also trap contaminants.

Odors such as food smells, pet smells, and moldiness are likely signs that contaminants are lingering in the air. If the smells are continuous, your home probably lacks adequate ventilation.

Visible Contamination

Be on the lookout for these visible signs of indoor air contamination:

  • Move a picture frame or hanging television to look for discolored walls, especially if someone in the household smokes.
  • Excessive dust that builds up on shelves, screens, and other static surfaces
  • Air filters in your home’s HVAC that get dirty quickly or need replacement more than once a season
  • Visible mildew or mold growth in your bathroom, laundry, or along window frames

How to Test Air Quality

Conduct an IAQ test immediately if you suspect that your home has poor air quality. It’s good practice to test your IAQ at least once a year even if you don’t think the air quality is poor.

There’s no single air quality test that detects all possible contaminants. Take a multilayered approach toward testing that includes continuous air quality monitors, always-on carbon monoxide detectors, routine mold tests, and radon tests. 

You can follow the steps below to ensure you’re protected.

1. Install Carbon Monoxide Detectors

Every home should have carbon monoxide detectors, especially if a gas heating system or gas stove is present. Install these detectors in your garage, in every major hallway, and in rooms that have gas appliances, such as your kitchen or laundry room.

Carbon monoxide detectors, which can be combined with smoke detectors, will alert you if levels become unsafe. They won’t sound for moderate or low levels of carbon monoxide.

2. Install Air Quality Monitors

Air quality monitors continuously test the air for potential contaminants and hazards, whether they’re solid particulates or colorless, odorless gases. Monitors work in one of two ways:

  • They detect the presence of toxins through electrochemical sensors
  • They monitor and estimate the amount of harmful particulates in the air through laser detection

Smart monitors check the air quality on the hour or once a day before sending the results to any connected devices. You can purchase a single portable sensor or can place units in multiple locations.

We recommend purchasing air quality monitors that track multiple different potential factors, including the following:

  • Carbon monoxide
  • Formaldehyde
  • Particulate matter from air pollution

3. Test for Mold

You can purchase different kinds of at-home mold tests at local stores or online. Swab tests can detect the general presence of mold on certain surfaces, while strip tests, which users send to labs, yield more specific results.

Professionals typically operate air pump mold tests, which provide even more detailed findings. We recommend starting with a simple swab or strip test first, and then progressing to more advanced testing once you’re certain that mold is present.

Mold can be found on window frames and surfaces that are close to moisture and high humidity. If mold gets into your HVAC, you’ll need to clean your AC unit to avoid its spread.

4. Test for Radon

Radon is a dangerous carcinogen, and it’s considered unsafe if it shows at least 4 picocuries per liter inside your home. The Environmental Protection Agency (EPA) recommends commissioning a radon test before you buy a home, before you sell a home, or if you don’t have proof of a passing test. Radon is typically associated with older homes, houses in the Southwest, and homes with basements.

There are two categories of radon testing devices: active devices that require power, such as radon monitors; and passive devices that don’t need power, such as alpha track detectors. Conduct a test immediately if you’re not sure whether your home has recently passed a radon test.

Air quality monitors range from simple and inexpensive indoor air pollution testers to pricier smart devices that continuously detect a full range of hazards.

Identify which toxins are likeliest to pose a hazard to your household before buying a monitor or test. Humid regions may also lead to humidity concerns in indoor environments, and homes with pets are likelier to have dander. You can use the EPA’s AirNow map to determine the air quality in your local community.

Once you know which air quality factors are potential threats and have set a budget, you can start to shop for air quality monitors that best suit you.

For General Air Quality Monitoring: Temtop M10 Air Quality Monitor

This air quality monitor covers most homeowners’ concerns at a reasonable price. The Temtop M10 monitors the following:

  • Air quality based on AQI
  • Formaldehyde levels
  • Particulate matter down to 2.5 microns in size

The interface displays which of the four factors are in the healthy range and which are not. Certain Temtop models allow for Wi-Fi connectivity for better tracking of trends over time.

For Carbon Dioxide Monitoring: SAF Aranet4 Home

This wireless IAQ monitor is more expensive than other models, but it does what many other monitors cannot: it detects the level of CO2 in the air. The monitor uses nondispersive infrared sensors to measure CO2, humidity levels, temperature, and atmospheric pressure. The SAF Aranet4 Home monitors trends over time and can send results directly to your mobile device.

The EPA doesn’t recommend specific air quality monitors to consumers, but it does provide testing resources and guides to low-cost air quality monitors . If certain air quality monitors are not within your budget, we recommend prioritizing carbon monoxide detectors, smoke detectors, and routine mold tests.

How to Improve Indoor Air Quality

Tests and monitoring equipment measure your home’s current air quality, but they don’t remedy dangers on their own. It’s important to take the following steps to actually reduce or eliminate potential hazards:

1. Take Note of Air Quality Monitor Readouts

Check the results of your IAQ monitor frequently. Monitors can alert you to issues such as high humidity. Act quickly to increase airflow and reduce toxins if and when you encounter such alerts.

2. Clean the Surfaces Around Your Home

Clean all surfaces that may host contaminants. These include the following:

  • Air ducts, which air duct cleaning services can address with pressure vacuums
  • Bathroom surfaces that may collect mold
  • Floors, which you should vacuum at least twice a week
  • Pet beds or furniture that holds onto dander and fur
  • Shelves and baseboards that collect dust and dander
  • Your stove and range hood, which may hang onto food contaminants

Hire professional mold remediation services if you encounter recurring mold in your home.

3. Increase Indoor Ventilation

Poor air circulation can worsen your home’s air quality. Turn on your home’s ceiling fans or open the windows when the air feels stagnant. Be sure to also check your HVAC filters once a month, or sooner if they regularly overfill. If filters are especially dirty, your heating and air conditioning system isn’t circulating and filtering the air effectively.

Your home’s IAQ is a vital component of preventing health issues for your household. Be on the lookout for any signs of potentially poor air quality. Install an air quality monitor in your home, add the appropriate number of carbon monoxide detectors for your home’s layout, and conduct radon and mold tests regularly.

Once you have a baseline understanding of your home’s air quality, take steps to improve it. Clean surfaces that host contaminants, take steps to improve ventilation, and alert professionals about unsafe living conditions.

How to Perform an Air Quality Test at Home FAQ

How can i test the quality of my air at home.

You can test the quality of air in your home by using air quality monitors or tests for specific hazards such as radon and mold. We recommend using multiple different sensors and air samples for comprehensive testing.

Are home air quality tests worth it?

Home air quality tests are worth it for the peace of mind they provide. You can address dangers that can lead to chronic health conditions by regularly testing your home’s air supply.

What are the symptoms of poor air quality in a house?

The symptoms of poor air quality in a house include respiratory infections, shortness of breath, headaches, and difficulty sleeping. Airborne toxins can exacerbate existing medical conditions.

How do I check my house for toxins?

Check your house for toxins by installing carbon monoxide detectors and a continuous air quality monitor. You can also test for lead, mold, and radon levels with specific at-home test kits.

What are the most common indoor air pollutants?

The most common indoor air pollutants are indoor particulates, combustion byproducts such as smoke, and volatile organic compounds. Homes can also host dangerous levels of lead and radon.

More on Home Improvement

Technician service removing air filter of the air conditioner for cleaning and maintenance.

How to Maintain Your Air Conditioner

If your HVAC system or air conditioner unit blows warm air, makes unusual sounds, or leaks, it may mean it’s time for a tune-up. Below,…

Sink basin with cleaning supplies on the counter and a woman cleaning the kitchen.

Cleaning Products Every Home Needs: A Room-by-Room Checklist

Keeping your living space neat and hygienic makes it more comfortable and relaxing, whether you’re deep-cleaning after moving into a new home or completing some…

HVAC maintenance worker cleaning air ducts for mold in family home.

How Much Does Mold Remediation Cost? (2024)

On average, mold remediation costs between $1,128 and $3,450 with an average cost of $2,230, but the cost substantially increases if the problem is widespread….

TIled floor with open floor HVAC vent cover removed

How Much Does Air Duct Cleaning Cost? (2024)

Air duct cleaning costs a national average of $725 but can range from $450 to $1,000. Routine air duct cleaning is vital for your central…

IMAGES

  1. 5 Easy ways to improve air quality in your city

    how to improve air quality in city

  2. How Trees Improve Air Quality

    how to improve air quality in city

  3. Insulwise Improves the Indoor Air Quality (IAQ) of Pittsburgh Area Homes

    how to improve air quality in city

  4. Greener Vision Improving Air Quality in Towns and Cities

    how to improve air quality in city

  5. Air Quality Guide- JHE Environmental

    how to improve air quality in city

  6. How You Can Improve Air Quality With 5 Simple Tips

    how to improve air quality in city

COMMENTS

  1. How to improve air quality in a city: from measurement to action

    Fortunately, local decision makers can rely on tighter regulations, cutting-edge technological sensors which facilitate measurement and inspiring best practices all around the globe. H2 How to tackle a global environmental and health issue and improve air quality in cities? H3 Regulation increases as scientific knowledge develops

  2. Clear the Air: 11 Solutions to Air Pollution in Cities

    Clear the Air: 11 Solutions to Air Pollution in Cities By Annie Granger Categories: Environment & Nature August 11, 2023, 3:21 PM Foto: CC0 Public Domain / Unsplash - photoholgic From small lifestyle changes to large-scale policy interventions, discover 11 actionable solutions to air pollution that can make a huge difference.

  3. Six impactful actions cities can take to improve their air quality

    Related Knowledge Bold action to improve air pollution can deliver swift and locally-felt rewards. These are the most impactful actions that city governments can take. We explain how to implement these measures in the related articles. Adopt WHO standards as your city's air quality target, monitor air quality and identify pollution priorities

  4. 5 ways cities are cleaning the air we breathe

    1. Boosting air quality monitoring Cities are following an evidence-based approach to implementing transformational changes. To do so, they are expanding their air quality monitoring networks to collect, analyse and communicate data about the air we breathe and the health impacts of air pollution.

  5. Actions You Can Take to Reduce Air Pollution

    Actions You Can Take to Reduce Air Pollution Follow these Tips Every Day to Reduce Pollution: Conserve energy - at home, at work, everywhere. Look for the ENERGY STAR label when buying home or office equipment. Carpool, use public transportation, bike, or walk whenever possible.

  6. How to improve air quality in a city: from measurement to

    Article How to improve air quality in a city: from measurement to action. Improving ambient air quality is core to the mission of local decision makers: it is both a public health and environmental issue. The challenge is quite a tall order: outdoor ...

  7. These five cities are taking aim at air pollution

    1. Paris, France Photo: AirParif The French capital has barred the most polluting vehicles from entering the city centre, banished cars from the Seine River quayside and reclaimed road space for trees and pedestrians.

  8. Learn how air quality improved in these cities

    ShareAmerica - May 2, 2022 Local governments in many cities are tackling long-standing air quality issues, and many of them see positive results. Here's how four large urban areas — Chicago, Los Angeles, Pittsburgh and New York — have made strides in helping their residents breathe easier. Chicago

  9. How we can improve air quality

    Minimize your exposure Monitor your air - Check local air pollution levels each day and be aware of guidance from city or national authorities, to determine whether to limit outdoor activity or avoid hotspots where air pollution levels may be elevated.

  10. How Can We Improve Air Quality In Cities?

    First, cities must follow the data. That is now easier than ever with the increasing availability of lower-cost air quality sensors, which can gather data more effectively and cost-efficiently ...

  11. Using green infrastructure to improve urban air quality (GI4AQ)

    While reducing pollutant emissions is always the most direct way to improve urban air quality, authorities world-wide have, with few exceptions, struggled to provide adequate air quality improvements through emission control strategies alone.

  12. Five cities tackling air pollution

    Earlier this year, it launched Breathe Warsaw, a partnership with Clean Air Fund and Bloomberg Philanthropies to improve air quality. Warsaw now has 165 air sensors across the city, the largest network in Europe, and Breathe Warsaw will use them to develop an air quality database, allowing officials to better understand pollution sources.

  13. 3 ways smart cities can improve air quality

    1. Increase data resolution. To improve air quality, cities must first achieve greater data resolution. Historically, air quality for an entire city has been measured at one or two geographic points for regulation compliance. However, concentrations of pollutants can change significantly over just a few city blocks, so measurements must be ...

  14. How Cities Can Effectively Improve Air Quality

    Giving Compass' Take: Grant Samms shares three recommendations on how smart cities can move forward on improving air quality in urban centers. How can donors participate in improving air quality? What role can you play? Read about air quality emissions regulations. What is Giving Compass?

  15. 10 Technologies to Improve Air Quality

    These are some of the technologies improving air quality in cities to make them better places to live and work. 1. Electric Vehicles. Many people sell their cars when they move to a populated downtown area, but everyone will still require some kind of vehicle for transportation.

  16. How can we improve air quality in cities?

    How can we improve air quality in cities? Gero Rueter hmf 01/23/2017 Air pollution poses a serious health risk in many European cities. But specific solutions are within reach. Image:...

  17. 4 ways cities are using low-cost sensors to improve air quality

    C40 Cities' new air quality monitoring report highlights 11 cities that have deployed these sensors: Addis Ababa, Dar es Salaam, Denver, Lima, Lisbon, London, Los Angeles, Mumbai, Paris, Portland, and Quezon City. Here are four ways cities are using low-cost air quality sensors to achieve a range of goals. 1.

  18. How Smart Cities Can Improve Air Quality

    Technology continues to advance and smart cities can implement technologies to capture high-quality data about air pollution levels. Before a city can take steps to mitigate these issues, it first needs to gather data from strategically chosen locations. Generally, air quality sensors have become smaller, affordable and more automated than before.

  19. Tackling poor air quality: Lessons from three cities

    In the early 1990s, Mexico City was known as the world's most polluted city and while there are still challenges, air quality has vastly improved. Daily concentration of SO2 - a contributor to PM2.5 concentrations - declined from 300 µg/m3 in the 1990s to less than 100 µg/m3 in 2018. PM2.5 levels currently are well below the WHO interim ...

  20. How Can Urban Policies Improve Air Quality and Help Mitigate Global

    The results systematize several policy approaches used around the world and suggest the need for more in-depth cross-city studies with the potential to highlight best practices both locally and globally. Finally, it calls for the inclusion of a more human rights-based approach as a mean of guaranteeing of clean air for all and reducing factors ...

  21. 10 things you can do to improve air quality in your city

    10 things you can do to improve air quality in your city Air pollution is an environmental issue that affects everyone. Here's how you can do your part in clearing the air. Use public transportation

  22. Salt Lake City, Utah Adapts to Improve Air Quality Through Smart Growth

    The plan set goals to improve air quality, protect community health, and reduce particulate matter (PM) and ozone pollution (which are both projected to be exacerbated by climate change). The city adopted specific transportation measures to decrease miles traveled, reduce vehicle idling, and promote alternatives.

  23. How these five global cities have improved their air quality

    2. Montréal, Canada (-54%) Montréal's emissions fell by 54% between 2008 and 2013. The city boasts many parks and waterways. Several projects were launched to preserve and expand the tree cover of the city to improve air quality and urban biodiversity.

  24. EPA rule that limits pollution is being challenged in the Supreme Court

    A key environmental effort to improve air quality and protect people from downwind pollution faces a legal challenge at the U.S. Supreme Court from several states and energy companies .

  25. Where people are moving to escape poor air quality

    About 1.2 million more homeowners and renters moved out of than moved into U.S. cities with high risk of poor air quality between 2021 and 2022, according to a new analysis by Redfin. While ...

  26. 5 ways to improve your Utah home's winter air quality

    Utah's winter outdoor air quality is often worse than major metropolitan cities like Los Angeles and New York City, and poor air quality can reduce Utahn's life expectancy by up to 3.6 years ...

  27. How To Perform An Air Quality Test At Home

    1. Install Carbon Monoxide Detectors. Every home should have carbon monoxide detectors, especially if a gas heating system or gas stove is present. Install these detectors in your garage, in every ...