What it means is the wind doesn't blow the pollution away and the fog keeps it trapped down in the same place.
Air pollution reached the highest band on the UK government's ten-point index across urban parts of England on Monday, according to The Guardian, as still and foggy conditions kept emissions trapped near ground level after a weekend of fireworks and bonfires. Government monitoring showed eleven sites, mainly in London and Greater Manchester, at "very high" levels for particulate matter in the twenty-four hours to 10am, with a further twenty-seven sites recording "high" levels across the capital, the north-west, the Midlands, Yorkshire and the east of England.
The worst reading was in Hillingdon, west London, where fine particles known as PM2.5 peaked at a twenty-four-hour average of 129 micrograms per cubic metre, more than eight times the World Health Organization's daily guideline. In the north-west, Manchester Piccadilly, Wigan, Blackburn, Preston and Rochdale all reached the "very high" band. Particulate matter consists of tiny solid particles and liquid droplets suspended in the air, and exposure is linked to heart and lung disease and cancer.
Jane Burston, chief executive of the Clean Air Fund, told the paper that monitoring networks could not determine the precise origin of the pollution, but that it was highly likely to stem from autumn celebrations. She cited a combination of foggy, windless weather with fireworks, 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 said, warning that people with asthma or lung conditions would have been especially at risk, and that concentrations in some of the worst affected areas were five to ten times above normal annual levels.
Larissa Lockwood, director of campaigns at Global Action Plan, said the levels were "not surprising at a time of year when people are lighting log burners, having bonfires and lighting fireworks", adding that normal pollution from transport and industry could not disperse because it was trapped by the fog. She identified domestic burning and transport as the biggest sources of particulate pollution and called for a public health campaign, "burn alerts" and the phasing out of non-essential burning in towns and cities.
The mayor of London's office said a high air pollution alert had been issued for Tuesday 10 November on the advice of forecasters at Imperial College London, noting that monitoring data showed pollution rising sharply across London from Friday to Sunday and remaining elevated into Monday morning. A Clean Air Greater Manchester spokesperson said higher particulate levels occur each year around Bonfire Night, with light winds and fog this year creating conditions in which pollution from a range of sources can accumulate near ground level. The government has been contacted for comment.
What the episode shows is that episodic spikes sit on top of a persistent baseline: as Burston argued, safer year-round air quality would make nights like Bonfire Night less likely to tip cities into extreme readings. The report does not quantify the share of the pollution attributable to fireworks, bonfires or Diwali, nor does it set out what enforcement or health measures, if any, will follow beyond the London alert and published Defra advice.
