Pollution haze over South East London, through a window in a viewing area of the 95-storey skyscraper The Shard, the tallest building in Britain, in London, Thursday, Jan. 19, 2017. The London mayor’s office says the city is experiencing a period of air pollution with pollution readings moderate to high across the city. (AP Photo/Matt Dunham)

A toxic air alert has been issued for London over the next three days, as Mayor Sadiq Khan warned of a “public health emergency”.

Official advice issued by the Department for the Environment says: “Adults and children with lung problems, and adults with heart problems, who experience symptoms, should consider reducing strenuous physical activity, particularly outdoors.”

Air pollution is set to hit a “high peak” in central parts of the capital including Westminster and the Square Mile, after rising to “moderate” in a total of 17 boroughs on Wednesday.


The London Air Quality Network, run by King’s College London, said there would be moderate-to-high air pollution Thursday.

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Under a system introduced by the mayor last year, air quality alerts are displayed at bus stops and subway station entrances during times of elevated pollution. Road signs instruct drivers to switch their engines off when stopped to reduce emissions.

Mayor Sadiq Khan has vowed to improve London’s worsening air quality. Some of the pollution comes from diesel vehicles, although Thursday’s alert is partly due to industrial emissions from continental Europe.