The way air quality is judged in UK planning is changing in emphasis. For years an air quality assessment (AQA) largely asked one question: does the scheme keep pollutant concentrations below the legal objectives? Increasingly, the profession and the regulator are asking a second, harder question: does it minimise people's exposure to pollution and the health harm that follows? This is the population-exposure shift, and it is quietly reshaping what a good AQA looks like in 2026.
This article explains what is driving the change, how it differs from a pure compliance test, and what it means for applicants preparing schemes now.
The old model: compliance with the objectives
UK air quality objectives set legal benchmarks — most familiarly the annual mean of 40 µg/m³ for nitrogen dioxide (NO₂), plus objectives for particulate matter (PM10 and PM2.5). A conventional AQA models concentrations at relevant receptors and checks them against those figures. If predicted levels sit below the objective, the scheme "passes". Our primer on NO₂, PM10, PM2.5 and NOx sets out what each pollutant is and why planners care.
Compliance still matters — you cannot introduce large numbers of new residents into air that breaches the objectives without a very good reason. But treating the objective as a finish line has a flaw: it implies that any level below 40 µg/m³ is equally acceptable. The health evidence says otherwise.
The new emphasis: exposure and health
There is no safe threshold for fine particulate matter. Health effects continue well below the legal objectives, which is why the World Health Organization guideline levels are far tighter than UK objectives. Reflecting that, Defra's interim PM2.5 guidance explicitly advises against a sole focus on compliance, placing greater weight on minimising pollution and reducing population exposure. The Institute of Air Quality Management (IAQM) has likewise signalled that its planning guidance is being updated to align with current health evidence and to give greater emphasis to health effects.
In practice this means an AQA is increasingly expected to show not just that a site is legally acceptable, but that the design has actively done what it reasonably can to cut exposure — for the new occupants and for neighbours.
PM2.5 and the Environment Act targets
The exposure shift is anchored in law through the Environment Act 2021 PM2.5 targets: a concentration target and a population-exposure-reduction target that pushes annual average exposure downwards over time. We cover these in detail in PM2.5 and the Environment Act targets. The population-exposure-reduction target is the clearest signal yet that policy is measuring success by how much everyone's exposure falls, not merely by whether hotspots stay under a line.
What this means for your application
If you are bringing a scheme forward in 2026, expect an AQA to do more than tick the objective box:
- Exposure-led layout. Habitable rooms, balconies and play space located away from the most polluted frontages; ventilation intakes sited on cleaner elevations. Small design choices that reduce what residents actually breathe.
- Demonstrable mitigation. Measures that cut emissions and exposure — from removing gas boilers (increasingly the default under the incoming energy standards) to electric vehicle charging, travel plans and green infrastructure.
- Air quality neutral, and beyond. In London, schemes must still show they are air quality neutral under London Plan Policy SI 1, as we explain in air quality neutral explained — but the exposure agenda pushes towards air quality positive where possible.
- Robust monitoring data. Assessments continue to rely on Defra background maps and local monitoring, adjusted using the National Bias Adjustment Factor — a reminder that the inputs matter as much as the method.
Does this mean every scheme needs a full AQA?
No. The screening logic still applies: small developments with limited traffic generation, away from Air Quality Management Areas and busy roads, may only need a short air quality statement rather than detailed dispersion modelling. What the exposure shift changes is the quality of thinking expected where an assessment is required — and the expectation that mitigation is genuine, not nominal. If your site sits within an Air Quality Management Area or beside a busy route, an exposure-led AQA is now the sensible default.
How Fortress Associates can help
Fortress Associates produces automated air quality assessments for UK planning applications, using live official datasets — Defra background maps, AQMA boundaries, monitoring data and DfT traffic counts — at the point of report creation. The report is free and ready in minutes, assessing NO₂, PM2.5, PM10 and NOx and following EPUK/IAQM planning criteria, Defra LAQM.TG(22), the NPPF and (for London sites) London Plan Policy SI 1. To get an assessment that reflects the current health-focused approach, contact us or see our full range of services.
Sources & further reading
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