Air pollution is a silent killer. Here's how cities are tackling it

Air pollution kills 13 people every minute worldwide and evidence continues to reveal new connections between polluted air and adverse health effects. As urbanization increases and air quality deteriorates, addressing emissions to protect public health is critical.

Cities worldwide are increasingly taking action to counter air pollution. 50 cities participating in C40's Cities Clean Air Accelerator and 35 cities from C40’s Green and Healthy Streets Accelerator are committed to launching innovative strategies and bold initiatives to clean their air and protect the wellbeing of residents.

The last five years have seen growth in new initiatives to reduce air pollution, from vehicle-access restrictions to electrification of public bus fleets and mitigation of on-site emissions from buildings.

Cities in the C40 Network are tackling their air pollution, ranging from waste-reduction initiatives to bolstering green public transport.

Transportation is a significant contributor to urban air pollution, prompting many mayors to implement stricter measures, such as restricting polluting vehicles from entering certain areas or entire cities. These actions, integral to broader initiatives aimed at achieving climate objectives and enhancing urban mobility, are transforming cities into healthier, more liveable communities.

London recently expanded its Ultra Low Emission Zone (ULEZ) to cover the Greater London area, creating the largest global clean air zone. Since ULEZ, nitrogen dioxide (NO2) levels have declined by almost 50% in central London, as compared to a scenario without the ULEZ. More than 95% of vehicles seen driving in London are now compliant with the ULEZ emissions standards, up from just 39% in 2017.

This has been supported through a £270m scrappage scheme by the Mayor of London, enabling over 60,000 Londoners, businesses and charities to replace or retrofit their older, polluting vehicles and switch to cleaner, greener modes of transport.

Policies in London, such as the central ULEZ, have contributed to reductions in the number of hospital admissions for asthma attributable to air pollution of 30% in 2017 to 2019, compared to the period between 2014 to 2016.

Madrid, Milan and Seoul, meanwhile, are expanding low-emission zones and imposing stricter limits on polluting vehicles. Warsaw will introduce the Strefy Czystego Transportu (SCT) in July 2024, limiting high-polluting vehicles in 7% of the city. Bogotá’s Urban Zones for Better Air (ZUMA), developed with local communities, targets pollution from transportation and industry to enhance air quality and public health whilst revitalizing public spaces.

Cities are also electrifying public transport to cut emissions and meet air quality targets. In three years, European and Latin American cities in the C40 Green and Healthy Streets Accelerator almost doubled electric bus numbers. London has 1,300 zero-emission buses, Seoul operates over 1,000 electric buses and 27 hydrogen fuel cell buses.

Santiago has 2,000 electric buses, 31% of its fleet, while Delhi operates 1,300 electric buses. Despite progress, cities encounter challenges in fully electrifying their vehicle fleets, including financing, building charging infrastructure and grid capacity constraints.

Cities are addressing emissions not only from transportation but also from buildings and energy production. They’re implementing initiatives to enhance building efficiency, enforce performance standards and shift away from fossil fuels for heating and cooking. Furthermore, they’re extending access to clean energy sources and providing essential services to informal settlements, such as household electrification.

A ban on using non-class coal and wood boilers in Warsaw began in January 2023. Since October 2023 this includes burning coal in households. In addition, Warsaw has provided subsidies and grants to replace domestic solid fuel heating systems for cleaner renewable heating alternatives since 2018.

Waste management, an important intervention in many cities in the global south, is a focus for signatories of the C40 Cities Clean Air Accelerator, especially in Africa. Sub-Saharan Africa collects 43% of urban waste (9% rural), with nearly 70% disposed of in open dumps. Interventions include composting, recycling and optimizing waste collection.

Dakar, for example, rehabilitates former waste burning sites, creating jobs for young people and curbing air pollution from open burning. Addis Ababa is expanding waste management with composting and recycling initiatives, emphasizing their vital role in curbing air pollution and promoting inclusive economic growth. Accra involves local communities in developing community waste separation programmes and Tshwane runs awareness campaigns on the health hazards of tire burning.

Central to these efforts is the expansion of air quality data, giving city officials insights into pollution levels and sources, and empowering residents with health-relevant information. Using innovative technologies, cities are expanding air monitoring capabilities, deploying lower-cost sensors to widen spatial coverage and identity pollution hotspots.

Signatory cities of the Clean Air Accelerator use low-cost sensors, with 35 of 50 cities using them in their air quality networks. Breathe London's network expanded from 136 to over 400 monitoring sites. Jakarta added 14 lower-cost monitors to its reference stations, offering extensive citywide air quality data. Quezon City positioned 21 new air monitors near sensitive locations, with plans for further expansion.

In September 2022, Warsaw launched a network expansion of 100 air quality monitors to their existing eight reference stations, with a further 57 sensors in 17 municipalities neighbouring Warsaw. Nairobi also expanded its network, deploying 17 air quality monitors that report real-time data to the public.

Despite efforts, raising awareness about air pollution sources and risks remains challenging. Surveys in cities worldwide show differing resident understanding of pollution sources and impacts, emphasizing the need for education. In Bogotá, although 92% think about air quality daily, many are unaware of primary pollution sources. This underscores the importance of initiatives to expand public awareness and support informed decision-making. London created innovative visual campaigns to expand public awareness and reduce emissions.

Global cities are at the forefront of the battle against air pollution, implementing bold initiatives to protect citizen’s health. Using regulation and innovative technology, urban centres deploy diverse strategies to achieve clean air.

Our Common Air, a new Commission working to catalyze global action on air pollution, has highlighted the need to engage subnational climate and health leaders. As momentum grows, it is vital that cities, national governments, advocates and the private sector work together to expand these initiatives, ensuring clean air becomes a reality.