High air pollution alert issued by London mayor

The London mayor has triggered a high air pollution alert for the capital with residents urged to take steps to protect their health and reduce emissions.

People should avoid actions that contribute to pollution, including leaving vehicle engines idling and burning garden waste, City Hall said.

Forecasters at Imperial College London advised the mayor to issue the alert, citing the likelihood of increased levels of ground-level ozone and the potential for higher levels of particulate matter due to dry conditions.

It comes as an amber warning for extreme heat has also been issued by the Met Office, with temperatures forecast to reach as high as 39C on Wednesday.

This is the second high air pollution alert issued in London this year.

Additional details have been shared with London's GPs and emergency departments to help support vulnerable patients.

High air pollution alerts are displayed across the capital, including on bus stop countdown signs and the London Underground. Alerts are also sent to schools and London boroughs when moderate, high or very high pollution levels are forecast.

The deputy mayor for environment and energy, Mete Coban, said: "Toxic air is responsible for thousands of premature deaths in London each year, which is why the mayor has done everything in his power to tackle it, which includes launching the world's largest clean air zone.

"It is really important we all do our bit to protect those who are most vulnerable."

According to City Hall, ground-level ozone is not emitted directly but forms through chemical reactions in the atmosphere involving pollutants such as nitrogen oxides and volatile organic compounds in strong sunshine.

Particulate matter concentrations can also be affected by weather conditions and pollution sources outside London, including from continental Europe.

The air pollution alert system was established by the mayor in 2016. Forecasts are produced by Imperial College London and checked against other public forecasts to predict when pollution levels are expected to reach moderate, high or very high levels.

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