15 July 2025
Air pollution across the UK dropped between 2015 and 2024, but dangerous levels are still reached too often, shows new research published today (Tuesday, 15 July) in Environmental Science: Atmospheres.
Scientists from the University of Reading studied pollution at more than 500 monitoring sites around the UK. They looked at three main types of air pollution which harm people's health. Two types of pollution got better over the decade. Nitrogen dioxide (NO2), which is mainly produced by traffic, fell by 35% on average at monitoring sites. Fine particles called PM2.5, which are small enough to get deep into lungs, dropped by 30%.
Despite these improvements, pollution still breaks safety limits too often. The average number of days each year when NO2 exceeded World Health Organization targets fell from 136 to 40 days, while for PM2.5 particles exceedances decreased from 60 to 22 days per year.
In contrast to NO2 and PM2.5, another pollutant, surface ozone (O3) increased by 17% on average over the decade. The number of days when O3, which is formed when sunlight interacts with NO2 and volatile organic compounds (VOCs) produced by traffic and industry, exceeded targets doubled from 7 to 14 per year.
Dr James Weber, lead author at the University of Reading, said: "The UK has made progress on air quality, but there is still a long way to go. Pollution from traffic is getting better, but we need both local action and international cooperation to improve all types of air pollution. The fact that O3 is getting worse while other pollution improves shows we need to think carefully about how we tackle this problem and not focus on pollutants in isolation.”
Different approaches are needed to cut pollution
The research highlight that different pollution types come from different sources. NO2 pollution is mainly driven by local traffic, while PM2.5 particles often blow in from other parts of the UK and continental Europe. Ozone pollution comes from both local and distant sources.
These findings mean different approaches are needed to tackle each type of pollution. Cleaner vehicles can help reduce NO2 from traffic, but cutting PM2.5 pollution needs national and international efforts because it can travel long distances across borders from continental Europe. O3 presents a complex challenge as its formation depends on the balance of certain gases in the atmosphere, their interaction with sunlight and temperature. In particular, as NO2 decreases, O3 will increase in most urban areas unless simultaneous efforts are made to reduce the VOCs which fuel its production, highlighting the need for multi-pollutant policies which span multiple sectors and countries.
Weber, J., & Dacre, H. F. (2025). UK air quality showed clear improvement from 2015 to 2024 but breaching of targets remains very common. Environmental Science: Atmospheres. Royal Society of Chemistry. https://doi.org/10.1039/d5ea00055f
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