The rapid breaching of the limits is a dramatic illustration of the illegal air pollution affecting most urban areas in the UK, which will see the government being sued in the high court for a third time early in 2018. High NO2 levels are estimated to cause about 23,500 early deaths a year.
London sites regularly break the annual limit in January
The law requires that hourly levels of toxic NO2 must not exceed 200 micrograms per cubic metre (µg/m3) more than 18 times in a whole year. But the most polluted places have vastly exceeded this: in 2016 Putney High Street broke the hourly limit over 1,200 times. The live charts use data from the London Air Quality Network, run by Kings College London, to show daily updates on how many hourly breaches have occurred.
The live map below shows the number of hourly pollution level breaches at all the monitoring sites in London. There is also an legal limit for the average NO2 level across the whole year: in 2016 this was broken at 59 of the 97 sites.
Nitrogen dioxide limits are broken across the city