Paris, Madrid, Athens and Mexico City are quitting diesel

Citing millions of deaths linked to air pollution worldwide every year, four major cities – Paris, Madrid, Mexico City and Athens, Greece – made an agreement on Friday to remove diesel vehicles from their streets by 2025.

The cities’ mayors made the announcement during the sixth C40 Mayors Summit in Mexico City – an annual meeting with leaders from as many as 90 of the world’s major cities. The four mayors on Friday vowed to create incentives for alternatives to diesel, an about-face from years of government encouragement in Europe for automakers to advance diesel technology, which can be more efficient than gasoline.

“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,” Mayor Anne Hidalgo of Paris said in a statement.

Europe has long grappled with striking an environmentally friendly balance with automakers. Diesel engines account for half of new car sales there, according to Bloomberg, and have led the world in advances to the fuel-efficient alternative to gas.

But some 3.7 million deaths are linked to outdoor air pollution every year, in addition to 4.3 million from indoor air pollution, according to the World Health Organization, making it the world’s single largest environmental health risk.

And while the vast majority of them occur in low- and middle-income countries, the WHO estimates that 92 percent of the population lives somewhere that does not meet its standards for healthy air. People who live in cities with high levels of outdoor air pollution have higher rates of heart disease, respiratory problems and lung cancers.

Diesel — the predominant fuel used to ship goods all over the world — presents a difficult trade-off because it can get more mileage and emit less carbon dioxide than gas, but the pollution it produces when it is burned creates more nitrogen oxide.

Such emissions are usually in the form of particulates or black soot and can pollute crops, animals, water resources and human lungs.

While the WHO continuously releases information about its impact on global health, it also gets easier every year to see firsthand how potent diesel pollution has become. In Paris it has been blamed for obscuring views of the Eiffel Tower. Air quality is also deteriorating famous world monuments in Rome.

“Big problems like air pollution require bold action, and we call on car and bus manufacturers to join us,” Hidalgo said in a statement on Tuesday.

But with pressure to reduce carbon emissions, automakers in Europe who have heavily invested in diesel have fired back against the prospect.

“The industry cannot reach the carbon-dioxide emission targets without diesel technology,” Carlos Ghosn, chief executive officer of Renault and president of the European Automobile Manufacturers’ Association, said at a news conference in June.