The mayors of 35 cities across the world have pledged to deliver clean air for the more than 140-million people that live in their cities, through the signing of the C40 Clean Air Cities Declaration.

The pledge, unveiled on Friday at the C40 World Mayors Summit in Copenhagen, commits cities to set ambitious pollution reduction targets and implement substantive clean air policies by 2025.

By publicly reporting on their progress, the cities plan to generate a “race to the top” in cleaning the air in the world’s big cities.

The cities that signed the C40 declaration are Amman, in Jordan; Austin, in the US; Bengaluru, in India; Barcelona, in Spain; Berlin, in Germany; Buenos Aires, in Argentina; Copenhagen, in Denmark; Delhi, in India; Dubai, in the United Arab Emirates; Durban, in South Africa; Guadalajara, in Mexico; Heidelberg, in Germany; Houston, in the US; Jakarta, in Indonesia; Los Angeles, in the US; Lima, in Peru; Lisbon, in Spain; London, in the UK; Madrid, in Spain; Medellin, in Colombia; Mexico City, in Mexico; Milan, in Italy; Oslo, in Norway; Paris, in France; Portland, in the US; Quezon City, in the Philippines; Quito, in Ecuador; Rotterdam, in the Netherlands; Seoul, in South Korea; Stockholm, in Sweden; Sydney, in Australia; Tel Aviv-Yafo, in Israel; Tokyo, in Japan; Warsaw, in Poland; and Washington DC, in the US.

According to the World Health Organisation (WHO), nine in ten citizens around the world breathe dirty air, while about seven-million people die prematurely each year owing to air pollution.

Air pollution is creating a global public health crisis – one that is rooted in social injustice. Typically, it is the poorest and most vulnerable communities that are most affected by dirty, polluted air.

Through the C40 Clean Air Cities Declaration, mayors commit to using their power and influence to reduce air pollution and work towards meeting the WHO’s Air Quality Guidelines.

This means that cities will continually reduce their local emissions and advocate for reductions in regional emissions, resulting in continuous declines in air pollution levels that move towards meeting the WHO guidelines.

Signatories of the declaration pledge to set ambitious pollution reduction targets within two years that meet or exceed national commitments, putting them on a path towards meeting WHO guidelines; implement substantive clean air policies by 2025 that address the unique causes of pollution in their cities and publicly report progress on achieving these goals.

If the 35 signatories reduce yearly average particle matter 2.5 levels to WHO guidelines (10 ug/m³) it could avoid 40 000 deaths a year. 

Mayors have an array of tools at their disposal for improving air quality, including expanding low- or zero-carbon public transport; creating zero-emissions zones; requiring and promoting cleaner fuels for heating and cooking; enhancing incentives and infrastructure to support walking and cycling, and establishing city-wide air quality monitoring.

However, they also recognise that cities often do not have the ability to address all causes of pollution and are calling on countries, businesses and all those who care about climate change and public health to match this commitment.

The declaration includes this message for all responsible actors: “We will use all the powers at our disposal as mayors to tackle air pollution and call on others responsible for the sources of air pollution that poison the air in our cities to match this commitment.”