London Air Quality
Greater London, United Kingdom · 9.5M population
Moderate
2024 avg
52
Annual AQI
2024 average
9.8 μg/m³
PM2.5
2.0× WHO limit
38 μg/m³
NO2
Annual avg (traffic)
5 μg/m³
WHO Limit
PM2.5 guideline
Monthly AQI Pattern
Monthly average AQI — worst in winter (wood burning + inversions)
London's Air Pollution Sources
Wood-Burning: The New Biggest Source
In a counterintuitive development, wood-burning stoves and open fires are now London's largest source of PM2.5 — overtaking traffic. Despite being used in only ~8% of homes, wood burners produce 31% of London's PM2.5 on winter evenings. London's Clean Air Act prohibits burning solid fuels in smoke control areas — but enforcement is limited and “Ecodesign” certified stoves are still permitted.
ULEZ: Tackling Vehicle NO2
The Ultra Low Emission Zone (ULEZ) charges non-compliant vehicles £12.50/day to enter Greater London. Since citywide expansion in August 2023, roadside NO2 dropped ~36% in the first year. The proportion of non-compliant vehicles fell from ~39% to ~20%. ULEZ has been most effective at reducing NO2 — less so for PM2.5, which is now dominated by wood burning rather than exhaust.
Saharan Dust Intrusions
London experiences 2–5 Saharan dust events per year, typically in spring and early summer when southerly winds carry Saharan dust across France and into the UK. These events push PM10 above EU daily limits and are exempt from the UK AQS standards. AQI can spike above 100 for a day or two, even when local sources are low.
The Great Smog Legacy
The Great Smog of December 1952 killed 12,000+ Londoners in five days, caused by coal smoke trapped in cold air over the city. It triggered the Clean Air Act 1956 — the world's first major air pollution legislation. Today's London is unrecognizably cleaner: PM2.5 is down from an estimated ~200 μg/m³ in the 1950s to under 10 μg/m³ today, though it still exceeds WHO limits of 5 μg/m³.
Frequently Asked Questions
What is the biggest source of air pollution in London?
Wood-burning stoves are now London's largest single source of PM2.5, accounting for ~31% of PM2.5 in winter. Road traffic remains the dominant source of nitrogen dioxide (NO2). The ULEZ has significantly reduced vehicle NOx, but wood burning (exempt from ULEZ) has grown in popularity, making it the hard-to-solve PM2.5 problem.
Has the ULEZ improved London's air quality?
Yes — notably for NO2. Roadside NO2 dropped ~36% in the ULEZ expansion area after citywide rollout in August 2023. Non-compliant vehicles fell from ~39% to ~20% of those driving in the zone. PM2.5 improvement is more limited because wood burning (the dominant PM2.5 source) is not affected by ULEZ.
When is London air quality worst?
December and January are typically worst — cold, calm high-pressure systems create inversions that trap wood-burning PM2.5 and vehicle emissions. Bonfire Night (November 5th) produces a single-night spike in PM2.5 across Greater London that is among the worst air quality events of the year.
Is London air quality worse than New York or Paris?
London's air quality is roughly comparable to New York (both ~AQI 52–58 annually) and slightly better than Paris (~55). All three exceed WHO PM2.5 guidelines of 5 μg/m³. Compared to most major cities in South and Southeast Asia, all three Western capitals have dramatically better air quality.