Fine particulate matter (PM2.5) poses significant health risks and is a growing focus of air quality regulation in England. With new targets set for 2040, understanding current trends and compliance pathways is critical.
In this article, Will reviews recent data on PM2.5 concentrations, assesses whether England is on track to meet these targets, and explores what developers can do to support air quality improvements through effective planning and mitigation.
Understanding PM2.5
PM2.5 refers to fine particulate matter with a diameter of 2.5 micrometres (µm) or less – approximately 30 times smaller than a human hair. These microscopic particles, which can include construction dust, combustion by-products, organic compounds, and metal fragments, can penetrate deep into the lungs and enter the bloodstream, posing significant health risks such as respiratory and cardiovascular issues.
Key sources include vehicle emissions, industrial activities, combustion processes, and construction operations. Understanding the sources of PM2.5 is essential for developers aiming to meet new planning requirements and mitigate air quality impacts on new and existing receptors.
New guidance
The interim guidance applies to future developments that have the potential to emit or are sensitive to PM2.5. It does not apply to planning decisions for applications submitted before 4 October 2024.
The guidance emphasises the importance of implementing appropriate mitigation measures during the design stage of new developments to minimise both PM2.5 emissions and exposure, rather than solely assessing the likelihood of exceeding the limit value.
Applicants must provide evidence in their planning applications that they have identified key sources of PM2.5 within their schemes and taken reasonable actions to minimise emissions of PM2.5 and its precursors.
Air quality targets
The Air Quality Standards Regulations (2010) set a limit value of 20 µg.m³, expressed as an annual average, for PM2.5.
However, the Environmental Targets (Fine Particulate Matter) (England) Regulations 2023 establish two new targets for PM2.5 to be achieved by 2040:
- A maximum annual mean concentration target of 10 µg.m³
- A population exposure reduction target of 35% compared to 2018
England’s progress to meet the targets
In England, annual average PM2.5 concentrations show an overall decrease as years go by. A likely reason for the reductions in concentration is the decline in PM2.5 emissions from source. The Department for Environment, Food and Rural Affairs (Defra) has published data1 comparing emissions of PM2.5 and their sources from 1990, 2005, 2022 and 2023. Overall, there is a significant reduction in emissions within the UK. Of the five major emission categories presented, only Domestic Combustion saw an increase in emissions between 2005 and 2022. Others, such as Industrial Process and Product Use, Road Transport and Industrial Combustion, have seen a decrease over time. Note that compared to 1990, all categories have seen an overall reduction over the last 30 or so years.
PM2.5 data insights
The rise in Domestic Combustion emissions of PM2.5 is likely attributable to the increase in popularity of home log burners. In the most recent years, Domestic Combustion was the greatest emitter of PM2.5.
Urban background concentrations
Defra also reports on the urban background concentrations of PM2.5. In general, annual average concentrations of PM2.5 at urban background sites have decreased from 12.4 µg.m3 in 2009 to 7.2 µg.m-3 in 2023. This shows a significant reduction in urban background PM2.5 concentrations and is encouraging when considering the new target of 10 µg.m³. That being said, background concentrations are influenced by both local and regional emission sources and will vary across the country.
In 2018 the annual average urban background concentration was 9.9 µg.m-3. Based on this data alone, a reduction of 3.5 µg.m-3 by 2040 is needed to meet a population exposure reduction target of 35%.
Roadside concentrations
Roadside concentrations have followed a very similar pattern to the urban background concentrations. The general trend in the data reported by Defra shows annual mean concentrations of PM2.5 at roadsides have decreased from 12.8 µg.m-3 in 2009 to 7.7 µg.m-3 in 2023. Again, this is encouraging when considering the new target of 10 µg/m³. That being said, roadside concentrations are highly variable and heavily influenced by the size, capacity and use of the adjacent road network.
In 2018, the annual average roadside concentration was 10.6 µg.m-3. Based on this data alone, a reduction of 3.7 µg.m-3 by 2040 is needed to meet the population exposure reduction target of 35%.
Covid-19 impacts
Between the years of 2015 and 2019, PM2.5 concentrations remained relatively unchanged. In 2020, a notable reduction in both urban background and roadside concentrations was observed, and concentrations have remained lower than the pre-pandemic levels ever since. A likely explanation for the reduction was the UK government’s response to the Covid-19 pandemic including multiple lockdowns during 2020 through to 2021 which restricted transport and changed the nation’s way of working as lockdown measures were lifted.
Assessing whether the new targets are enough
There is no safe level of exposure to air pollution. A recent study from the University of Technology Sydney has demonstrated a link between low-level PM2.5 pollution and liver damage and fatty liver disease in mice. Mice were exposed to 10 µg of PM2.5 a day consistently for four, eight and twelve weeks. They concluded that prolonged exposure to low-dose traffic-derived PM2.5 promotes pathological changes in the liver. Another recent study (Faherty, T., Raymond, J.E., McFiggans, G. et al, 2025), published in Nature Communications, also suggests that short-term exposure to particulate matter can impact brain function with results showing significant reductions in selective attention and emotion expression discrimination.
As more research into PM2.5 effects is conducted, we are likely to see targets adjusted to further reduce exposure of the population to harmful pollutants. Currently, the Environmental Targets (Fine Particulate Matter) (England) Regulations 2023 new annual mean concentration target for PM2.5 of 10 µg.m3 matches the World Health Organisation’s (WHO) interim target 4. However, the WHO’s guideline level for annual mean PM2.5 is 5 µg.m-3, half that of the new Defra target.
PM2.5 progress and planning application requirements
Over the last 20 years, the UK has seen significant reductions in PM2.5 emissions and concentrations at both urban background and roadside locations. However, according to the Institute of Fiscal Studies, 96% of the population of the UK live in areas above the WHO’s guideline level of 5 µg.m-3. Defra’s new guidance requires applicants to provide evidence in their planning applications that they have identified key sources of PM2.5 within their schemes and have taken reasonable actions to minimise emissions of PM2.5 and its precursors. One common emission source is road transport, and the latest version Defra’s Emissions Factors Toolkit suggests that electric cars are less polluting than their petrol and diesel equivalents, a positive sign for new developments that are seeking to promote electric vehicle usage.
When comparing like for like emission factors for 1,000 Light Duty Vehicles (LDVs), across five different speed scenarios (16 kph, 32 kph, 48 kph, 64 kph and 80 kph), there was an average reduction of 21.8% if 1,000 petrol LDVs were replaced entirely by EV LDVs and an average reduction of 22.9% if 1,000 diesel LDVs were replaced entirely by EV LDVs.
Our air quality expertise
Developers can aid in the reduction of national PM2.5 concentrations, and the exposure to it, by actively working with air quality consultants to appropriately select sites, effectively plan the site layout to minimise exposure for new occupants and existing receptors and implement effective site-specific mitigation measures.
Our air quality consultants have expertise in modelling various sources of PM2.5 to quantify their impacts. We can help you with modelling road traffic emissions from construction and operational phases of your projects including different fleet compositions. We also have expertise in modelling point source emissions from data centres, energy from waste facilities, short-term operating reserves, back-up generators and boilers (as well as other sources).
About the author
Will Hunt
Will Hunt is a principal air quality consultant, part of our team in Brighton, England.
Will has worked on several projects including assessing construction and operational effects of proposed developments, air quality neutral assessments for developments in London, modelling traffic emissions for site suitability and impacts on existing receptors. He has modelled point source emissions for short-term operating reserve facilities, energy from waste facilities, special waste incinerator plant, paint spraying facilities, odour abatement stacks and back-up generators for data centres, assessing both the impacts on human and ecological receptors. Will has also prepared many dust management plans for road schemes, permitted developments and residential schemes as well as monitoring method statements for dust during demolition and construction.
Will has a BSc (Hons) in Earth and Ocean Science.