More than two million Londoners are living in areas with illegal levels of air pollution, figures published by the city’s mayor Sadiq Khan show.
Updates from the London Atmospheric Emissions Inventory which analyses air quality in the capital, show that more than 400,000 children among those living in parts of the city which exceed the legal limits for pollution.
Mr Khan said the analysis showed there were no significant improvements in pollution between 2013 and 2016, when his predecessor Boris Johnson was in office.
In 2016, more than 400 schools were still in areas with toxic air.
While the number of primary schools in parts of the city where pollutant nitrogen dioxide exceeded legal limits was down slightly in 2016 compared to 2013, the number of secondary schools in polluted areas was up.
But there have since been significant improvements in measured pollution levels, he said.
Air pollution is down, with a 57% reduction in the number of hours recorded in which the city bust the legal limit for nitrogen dioxide so far this year compared to the same period last year.
In the first three months of 2016, 43 monitoring sites in London recorded hours exceeding their legal limit of nitrogen dioxide – with 13 going over the annual maximum of 18 hours above the cut-off.
But so far in 2019, just 10 monitoring sites have recorded breaches of the hourly limit, and none have hit the annual maximum threshold.
The figures come ahead of the introduction of the ultra low emission zone (ULEZ) which will charge the most polluting cars, motorcycles and vans £12.50 a day to drive in the city centre, and £100 for lorries, buses and coaches.
Officials said hourly breaches of nitrogen dioxide limits were almost exclusively due to traffic, and the improvements are likely to be down to cleaning up Transport for London buses and drivers already complying with the ULEZ.
Mr Khan said: “From the very outset I have been crystal clear that I would do everything in my power to tackle London’s toxic air crisis.
“So far in my mayoralty, this includes cleaning up our bus and taxi fleet and establishing the largest air quality monitoring network of any major city.
“The introduction of the world’s first 24-hour seven-day-a-week ultra low emission zone next week marks a watershed moment in our fight to clean up our filthy air.”
He added: “The data I’ve published today gives an even clearer picture of the urgent need to take action.”
Polling by YouGov ahead of the introduction of the ULEZ suggests 80% of Londoners and 90% of drivers know something about the scheme – although only one in five motorists are expected to drive into the central zone.