evidence: Illegal levels of air toxins found in many boroughs - Levels of the toxin nitrogen dioxide (NO2) in the air at five or more locations in 14 London boroughs were found to exceed the UK legal limit of 40 µg/m3 during tests - In total, sites in 31 boroughs had levels of the pollutant that exceeded the recommended limit set by the World Health Organisation - The single highest concentration of NO2 was found at Harlesden High Street - The mayor of London believes the study results make the case for the controversial expansion of the Ultra Low Emission Zone [...] - The WHO's recommended limit of nitrogen dioxide (10 µg/m3) was exceeded at all 1, 823 locations tested across 31 boroughs - A UK legal limit (40 µg/m3) was exceeded in five or more locations in 14 boroughs: Brent, The City of London, Croydon, Ealing, Greenwich, Hammersmith & Fulham, Hackney, Havering, Kensington & Chelsea, Lambeth, Merton, Richmond, Southwark and Wandsworth - In total, illegal levels of NO2 were found at one of more sites in 26 boroughs - The locations with the highest concentration of nitrogen dioxide were Harlesden High Street, Romford Town Centre and Wembley High Road [...] And while WHO limits are lower than the UK’s legal limits, it’s important to remember health experts say there is no proven safe level of pollution.