When Sadiq Kahn was elected mayor of London in 2016, more than 2 million people in the capital were living in areas with illegal levels of air pollution. Three years later, that number fell to 119,000, all thanks to a number of ambitious policies enacted by the mayor, aiming to improve air quality in the city.

According to a recent report, since Sadiq Khan became mayor of London, air pollution has plunged in the city, with a 94 percent reduction in the number of people living in areas with illegal levels of nitrogen dioxide (NO2) — a pollutant that’s particularly dangerous to human health. The number of schools in such areas has fallen by 97 percent, from 455 in 2016 to 14 in 2019.

The new report, which does not include the further falls in air pollution as a result of the COVID-19 lockdown in March, shows that NO2 levels in central London fell by 44 percent between early 2017 and early 2020.

The dramatic improvements in air quality are primarily attributed to ambitious regulation to curb traffic in the city, including charges that have deterred diesel-powered vehicles from entering the city center and have encouraged the use of cleaner vehicles. Putting low-emission buses on the dirtiest routes, ending licensing of new diesel taxis, and creating more bike-friendly spaces have also contributed to the positive change in air quality.

“The changes in NO2 in central London and along main bus routes were some of the fastest that we’ve ever measured” in 30 years of monitoring, said Dr. Gary Fuller, an air pollution expert at Imperial College London. “These successes show that our city’s air pollution is not an intractable problem.”