Four major cities are taking up the fight on air pollution by clamping down on diesel engines. The ban should come into full effect by the middle of the next decade.

Diesel engines will be banned from Paris, Mexico City, Madrid, and Athens sometime in the next ten years to promote cleaner transport such as alternative vehicle use or old-fashioned walking and cycling. The announcement was made at the C40 conference in Mexico.

Diesels were originally promoted by governments as test runs showed they released lower levels of CO2 and other harmful emissions. But, this type of engine has (rightfully) come under a lot of flak recently, particularly in urban areas, after it became apparent that manufacturers faked the results (you can read about it here). They have been linked to nitrogen oxides (NOx) and particulate matter (PM) emissions, which can build up in huge quantities in cities.

Fine PM, such as PM2.5, can pass into the bloodstream and contribute to heart or lung conditions (both acute and chronic), even death. At ground levels, NOx emissions can lead to ozone build-ups, causing breathing difficulties even for those without a history of respiratory problems. The WHO estimates that around three million people each year die due to exposure to outdoor air pollution.

In some cases, such as London, citizen groups have taken matters into their own hands. Environmental groups have championed their case and appealed to courts for clean air standards and regulations. Mayor Sadiq Khan has proposed an expansion of the planned Ultra-Low Emissions Zone, and campaigners are pushing for him to phase out all diesels from London by 2025.

“In the UK, London’s mayor is considering bolder action than his predecessor, proposing an expansion to the planned Ultra-Low Emission Zone. This is welcome but we want him to go further and faster,” said ClientEarth lawyer Alan Andrews.
“And it’s not just London that has this problem, we need a national network of clean air zones so that the problem is not simply pushed elsewhere.”

Keen on preventing such troubles at-home, mayors from four other cities with long-standing air pollution problems have pledged to use their executive power to limit the use of diesel engines. The four mayors declared that they would ban all diesel vehicles by 2025 and “commit to doing everything in their power to incentivize the use of electric, hydrogen and hybrid vehicles”.

“It is no secret that in Mexico City, we grapple with the twin problems of air pollution and traffic,” said the city’s mayor, Miguel Ángel Mancera.

“By expanding alternative transportation options like our Bus Rapid Transport and subway systems, while also investing in cycling infrastructure, we are working to ease congestion in our roadways and our lungs.”

Paris has already laid down some groundwork on the issue. Cars registered before 1997 are already banned from entering the city. The Champs-Élysées is closed to traffic once every month, and a 3-km long stretch on the Seine — once a two-lane motorway — has been recently pedestrianized. The city’s mayor, Anne Hidalgo, said that they will continue to “progressively ban the most polluting vehicles from the roads” of Paris.

“Our ambition is clear and we have started to roll it out: we want to ban diesel from our city, following the model of Tokyo, which has already done the same.”

Manuel Carmena, Madrid’s mayor, has spoken in support of cleaning city air saying it’s intimately tied with our efforts of tackling climate change. All in all, these four mayors seem to be set on cleaning the air, and they have their sights set on diesels.

Which is a big deal, because if major cities go down this road, they will set a powerful precedent for others to follow suit. Carmakers, too, are likely to understand this and push for the development of hybrid and electric cars even more than before. Hopefully, this time somebody will double-check their results before the WHO has to issue another grisly statistic.

Enjoyed this article? Join 40,000+ subscribers to the ZME Science newsletter. Subscribe now!