We knew that London’s air was dirty , but not this dirty. England’s capital belches so much filth into its air that it managed to breach its 2017 pollution limit in just five days . That’s not the whole city–if you go for a bracing stroll up on Hampstead Heath then you’ll still be able to get a lungful of fresh-ish air–but London’s pollution hotspots are already hitting their limits.

The culprit is nitrogen dioxide. The toxic gas is permitted to exceed 200 micrograms per cubic meter just 18 times in a year. In Brixton Road, Lambeth, it already passed that limit. Other pollution danger zones, like Putney High Street, and the iconic Oxford Street, are expected to hit their limits soon.

[Photo: sborisov/iStock]

Cleaning up London’s air, which kills around 10,000 people a year, is a priority for mayor Sadiq Khan. The best way to stop nitrogen dioxide pollution, which is caused by diesel engine emissions, is to get rid of as many cars as possible. One way to do that is to switch as many city services as possible to electric, which moves the pollution away from cities. London has already invested in electric delivery vehicles to curb emissions, and recently Khan announced that he is spending $1 billion on cycling over the next five years, double that of previous mayor Boris Johnson.

By 2050, more than 70% of the world’s population will live in cities or urban areas, up from 54% today. Clean air will be an essential resource. Private vehicles and big trucks have no place in our cities. The answer is to remove them as much as possible and to replace them with excellent public transit and cycling. That seems like a big job, because it is, but plenty of cities are already managing it, and once you crack the political barriers to banning cars, investing in transit can’t be more expensive than dealing with the people made sick, or killed, by the polluted air.