High pollution alert issued in London after PM2.5 levels exceed WHO limits by 8 times

A high pollution alert has been issued in London for Tuesday as dense fog caused particle pollution levels to exceed World Health Organisation (WHO) guidelines, threatening traffic disruptions and transport delays. Dense fog engulfed several parts of London, prompting authorities to issue a high pollution alert. (Reuters)London Mayor Sadiq Khan said he was issuing a high air pollution alert for Tuesday (November 10) and urged everyone in the UK capital to "minimise their exposure" by following health advice. The mayor's office said that smoke from Bonfire Night and Diwali fireworks were also likely contributors to the smog."Please switch off engines when idling and avoid burning garden waste, which contributes to pollution," he said.According to an official statement, high levels of particle pollution are forecast for Tuesday after dense fog and very light winds allowed pollution to build up over the weekend.London pollution levels exceeding WHO limitsAccording to The Guardian, government monitoring sites showed 11 locations, mainly in London and Greater Manchester, reached the highest band on its 10-point index for particulate matter in the last 24 hours till 10 am as calm winds and foggy conditions prevented pollutants from dispersing. At least 27 sites recorded "high" levels across London, Yorkshire and the east of England.Hillingdon in west London recorded the worst pollution reading, with PM2.5 levels reaching 129 micrograms per cubic metre at a 24-hour average, more than eight times the daily guidelines set by the WHO. Several north-western areas like Manchester Piccadilly, Wigan, Blackburn and Rochdale recorded "very high" pollution levels.Forecasters at Imperial College London advised Khan to sound the alert as government monitoring also recorded high pollution in the South East of England and East Midlands, according to Sky News. The London Mayor advised people to contribute to reducing pollution by using public transport more frequently, switching off engines and avoiding unnecessary burning at home.Mete Coban, the deputy mayor for environment and energy, 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."Travel disruptions fearedEarlier, the London Meteorological Office issued a yellow fog warning for parts of England and Wales until 10 am (local time), with visibility reduced to less than 100 metres in some places. The office warned of delays to public transport, with chances of flights being delayed or cancelled.London Met Office chief meteorologist Jason Kelly said persistent high pressure has brought light winds and clear skies, allowing fog to form, while "weak November sunshine has meant it is fairly slow to clear"."We're expecting one more night of dense fog, with a warning in place for some areas. Increasing cloud and wind should then limit further widespread fog from developing," he was quoted as saying by the BBC.Weather played key roleJane Burston, the CEO of the Clean Air Fund, said the pollution levels in London resulted from a combination of existing weather conditions and recent celebrations."It’s a combination of the weather, which has been foggy and not windy at all, and then the fireworks and bonfires and Diwali. What it means is the wind doesn’t blow the pollution away and the fog keeps it trapped down in the same place," she told The Guardian.A Clean Air Greater Manchester spokesperson said weather conditions played an important factor, with "ight winds and fog creating conditions in which pollution from a range of sources can accumulate near ground level."