London issues high pollution alert as fog and fireworks trap bad air

A high air pollution alert is in place across London after a weekend of dense fog and fireworks trapped dangerous emissions close to the ground, even though actual pollution levels were lower than expected. Forecasters at Imperial College London advised the mayor, Lord Khan, to trigger the alert for Tuesday after moderate pollution was forecast over the weekend of 7 to 8 November. Direct alerts went out to schools, councils and care homes from 5 to 8 November. The mayor's office shared extra details with London doctors and emergency departments to help vulnerable patients. According to The Guardian, government monitoring showed 11 sites across England reached the highest band on its index for particulate matter, with Hillingdon in west London seeing fine particles peak at more than eight times the World Health Organization's daily guideline. City Hall displays high pollution warnings at public spots across the capital, including bus stop countdown signs and the Underground. Londoners have been advised to walk, cycle and use public transport more frequently, drive less and avoid unnecessary burning at home. This is the fourth alert issued in London this year, following the last one in June during a heatwave. Met Office chief meteorologist Jason Kelly noted that persistent high pressure brought light winds and clear skies, allowing fog to form, while weak November sunshine meant it cleared slowly.

Context

Air pollution alerts are typically issued by city authorities when still weather conditions trap harmful particles near the surface. This happens more often during colder months when low wind speeds combine with domestic heating and seasonal events.