Most parents assume the air quality in their child's school is safe. According to the latest available DEFRA annual average data, it almost certainly is not, at least not by the standard that matters most.
We analysed PM2.5 air quality in schools across England and Wales using the latest available DEFRA annual average data, mapping figures across all 174 local authorities.
Of the 174 local authorities 160 were found to exceed the WHO air quality guidelines for PM2.5, which is 5 micrograms per cubic metre. Of the 14 that met them, 13 were in rural Wales and one in England. Everywhere else, children are breathing air that the world's leading health authority says carries long-term risks.
You can look up the air quality at your child's school right now at: airqualitymonitors.net/pages/school-air-quality-calculator
What the Standards Actually Say
To understand the scale of the problem with air quality in schools, it helps to look at how different countries and institutions have set their limits for PM2.5, fine particulate matter small enough to pass through the lungs and into the bloodstream.
WHO: 5 µg/m³
The World Health Organisation sets its guidelines based purely on health evidence. Its annual guideline for PM2.5 air quality is 5 µg/m³. Long-term exposure above this level is associated with reduced lung development in children, increased rates of asthma and respiratory infection, cardiovascular disease and premature death. Children are particularly vulnerable because their lungs are still developing and they breathe proportionally more air than adults.
United States: 9 µg/m³
In February 2024, the US Environmental Protection Agency strengthened its annual PM2.5 standard from 12 µg/m³ to 9 µg/m³. Notably, the current US administration has since moved to vacate this revised standard, which would revert the limit to 12 µg/m³. Even at 12 µg/m³, the US standard is tighter than the UK's current legal limit.
European Union: 10 µg/m³ from 2030
In late 2024, the EU formally adopted a revised Ambient Air Quality Directive, cutting its annual PM2.5 limit from 25 µg/m³ to 10 µg/m³, to be enforced by 2030. This is the most significant tightening of EU air quality law in over 15 years.
United Kingdom: 20 µg/m³ now, 10 µg/m³ proposed for 2040
The United Kingdom's current legal annual limit for PM2.5 is 20 µg/m³, four times the WHO guideline. The UK government has proposed tightening this to 10 µg/m³, but not until 2040, a full decade after the EU's equivalent target. The reason is not scientific. A tighter legal limit would require the government to take substantive, costly action on traffic, industry and domestic burning much sooner. A 2040 deadline defers that obligation by a generation.
Where is the problem worst?
London dominates the rankings for poor air quality in schools. The worst local authority is the City of London, with an average PM2.5 across its schools of 10.95 µg/m³, more than double the WHO guideline, and the only LA in England and Wales whose average breaches the incoming EU 2030/UK 2040 standard of 10 µg/m³.
At individual school level, dozens of schools in inner London also breach the 10 µg/m³ limit. The worst is City of London School for Girls at 11.27 µg/m³, followed by St Paul's Cathedral School and the Fashion Retail Academy, both also at 11.27 µg/m³. Schools in Tower Hamlets, Westminster, Islington, Camden, Hackney, Southwark, Kensington and Chelsea, Lambeth and Hammersmith and Fulham all include individual schools recording above 10 µg/m³.
The top 33 worst local authorities for school air quality are all London boroughs. The first non-London local authority is Thurrock in Essex at 34th, averaging 8.08 µg/m³.
Outside London the picture is still serious, even if no individual school breaches the EU 2030 limit. The worst non-London school in England is Leighswood School in Walsall at 9.51 µg/m³, just below the incoming EU threshold but almost double the WHO guideline. Audenshaw School in Tameside records 9.31 µg/m³, Broad Heath Community Primary in Coventry 9.32 µg/m³, and Eden Boys' School in Birmingham 9.24 µg/m³. All four would breach the US EPA's current standard of 9 µg/m³ and all exceed WHO guidelines by a significant margin.
Outside the South East, the problem is worst in the West Midlands. Sandwell and Walsall both average 8.03 µg/m³ across all their schools, Birmingham 7.91 µg/m³. Manchester sits at 7.70 µg/m³, Leicester at 7.85 µg/m³.
Even relatively rural areas are not exempt. Hampshire, with 579 schools, averages 6.23 µg/m³, 25% above the WHO guideline. North Yorkshire, with 370 schools, averages 5.38 µg/m³. Bath and North East Somerset averages 6.01 µg/m³.
The 14 local authorities that meet WHO guidelines
The only local authorities where children attend schools within WHO air quality guidelines are almost entirely in rural Wales. Pembrokeshire has the cleanest school air in England and Wales at 3.91 µg/m³. Ceredigion, Isle of Anglesey and Gwynedd all average below 4.5 µg/m³. Powys, Cumberland, Carmarthenshire, Conwy, Westmorland and Furness, Swansea, Neath Port Talbot, Denbighshire, Bridgend and Northumberland complete the list.
Northumberland is the only English local authority where the average PM2.5 across its schools falls within WHO guidelines, at 4.93 µg/m³. Every other local authority in England, all 151 of them, has average school air quality above what the WHO considers safe.
Why the government is slow to act
The gap between what the science says and what the law requires is not an oversight. It is a choice.
Tightening the UK annual PM2.5 limit to 10 µg/m³ would bring 160 out of 174 local authorities within compliance at the average school level. But it would also create a legal obligation to act: reducing traffic emissions, regulate domestic wood burning, control industrial pollution and invest in clean air infrastructure. A 2040 deadline defers that obligation by a generation.
The EU faced the same political challenge and chose to act by 2030. The US EPA, even with its standard now under political pressure, moved to 9 µg/m³.
In thirty years, I believe we will look back on this period the way we now look back on second-hand smoking, with disbelief that we allowed it to continue for so long while the evidence of harm was already clear. We never thought about the consequences of second-hand smoke thirty years ago. We are making the same mistake air pollution today.
What parents and schools can do now
The defra air quality data for every school in England and Wales is publicly available. Parents can search for their child's school by name at airqualitymonitors.net/pages/school-air-quality-calculator and see the PM2.5 figure immediately, based on official DEFRA 2024 annual average data.
For schools that want to understand what is happening inside the classroom, where outdoor pollution enters through windows and can accumulate, continuous indoor air quality monitoring is available without the need for WiFi, mains power or IT infrastructure. Real-time data on CO2, PM2.5, temperature and humidity gives school leadership and facilities teams the information they need to take action, whether that means improving ventilation, reducing traffic at the school gate or making the case to their local authority for cleaner air around the school site.
The law has not caught up with the science. The data has.
About the author
Edward Wright has been thinking about urban air quality since long before it became a policy issue. Cycling through London daily for years, he became acutely aware of the diesel fumes from buses and the invisible particulate matter thrown up by traffic. He studied Chemistry at A Level, planted trees in every city he has lived in, and spent years working in financial technology at Credit Suisse and Citigroup before founding AirQualityMonitors.net and becoming an official partner of Clear The Air environmental monitoring sensors.
'Thirty years ago we never really thought about the consequences of second-hand smoke,' he says. 'In thirty years I think we will be outraged that most of the population of the planet lived next to roads where combustion engines ran day and night. And it is not just exhaust fumes. PM2.5 from brake pads and discs has actually increased as EVs become more common, because they are so heavy. The problem is broader than most people realise.