The mayors of Paris, Mexico City, Madrid, and Athens have pledged to ban diesel vehicles from their cities by 2025 in an effort to improve air quality. The announcement was made in Mexico at the C40 Mayors Summit, a gathering of cities committed to addressing climate change.

These four cities also pledged to incentivize alternative vehicles and promote walking and cycling infrastructure. The World Health Organization reported that worldwide, three million deaths each year are linked to exposure to outdoor air pollution, with the vast majority of these deaths occurring in cities.

“Mayors have already stood up to say that the climate change is one of the greatest challenges we face,” said Anne Hidalgo, mayor of Paris and new chair of the C40 Cities Climate Leadership Group, in a release. “Today, we also stand up to say we no longer tolerate air pollution and the health problems and deaths it causes — particularly for our most vulnerable citizens. Big problems like air pollution require bold action, and we call on car and bus manufacturers to join us.”

Citizens across the world have joined a petition demanding that vehicle manufacturers lead an air quality transformation, according to C40. They are urging the companies to stop producing diesel vehicles by 2025 and to support a rapid transition to electric, hydrogen, and hybrid vehicles.

There are 86 affiliated cities in the C40 network, including 12 from the U.S. These 12 cities have already taken nearly 2,400 individual actions to respond to climate change in the past decade, according to a C40 report.

The C40 Mayors Summit isn't the only place where officials from around the world have have pledged to reduce vehicle emissions. On Nov. 16 at the Marrakech Climate Change Conference (COP22) in Morocco, eight countries signed an agreement to increase the share of electric vehicles in their government fleets and called for other governments to join them. These countries are: Canada, China, France, Japan, Norway, Sweden, the United Kingdom, and the United States.