London's AQI is below 100, but PM2.5 levels are 5 times WHO guideline: What's behind the air pollution alert?

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London issues warning as fog and fireworks raise pollution

London issued a high air pollution alert for Tuesday after fog and fireworks were linked to poor air quality. BBC News reported that Mayor Sadiq Khan warned hospitals and schools about expected pollution, while the Evening Standard said the alert followed advice from Imperial College London forecasters. Hindustan Times and India Times reported that PM2.5 levels were eight times the WHO limit; other reports focused on fog and fireworks without giving that figure. Xinhua reported that fireworks and bonfires contributed to pollution in Britain.