Air pollution has been a topic of significant interest in the planning system for some time, but the approach to the consideration of particulate matter emissions is evolving.
The Department for the Environment, Food and Rural Affairs (Defra) is proposing a new approach for looking at fine particulate matter (PM2.5) and planning.
Separate but related regimes
The regime for Air Quality Standards already sets ‘limit values’, ‘target values’ and ‘long-term objectives’ for ambient concentrations of key pollutants. Limit values are legally binding parameters that must not be exceeded. The Secretary of State for Environment, Food and Rural Affairs is responsible for meeting the limit values in England.
Local authorities are required to work towards the UK’s Air Quality Strategy (including putting in place an action plan with pollution reduction measures).
The Environment Act 2021 required long-term targets to be established for fine particulate matter (PM2.5) – now set through the Environmental Targets (Fine Particulate Matter) (England) Regulations 2023. PM2.5, small particles of solid matter and liquid droplets in the air, smaller than 2.5 microns in diameter, can be inhaled and enter the bloodstream, causing a range of health issues. These can be naturally occurring, including from pollen and sea spray, but also result from industrial processes, combustion and the wearing of tyres and brakes in road transport. The government reports that while levels of fine particulate matter have been falling since the 1970s, the rate of decrease has slowed in recent years, and of course people living and working in areas with high levels of PM2.5, that isn’t the result of wholesome sea spray, may want to see levels fall further.
The new targets, set by the 2023 Regulations, are at a level scientists anticipate will not have a negative impact on human health during long term exposure, setting targets of:
- a maximum annual mean concentration target of 10µg/m3 to be achieved by 2040; and
- a population exposure reduction target of 35% compared to 2018 to be achieved by 2040.
New Planning Guidance
Defra is developing guidance on how to consider PM2.5 targets in planning decisions. Existing guidance focusses on whether development is likely to increase the risk of exceeding a legal limit or threshold in its location. Defra has issued interim guidance to provide developers and planning authorities with clarity on how to consider the targets, while the full guidance is under development.
The brief Interim Planning Guidance now:
- Requires impact on all ambient air to be understood, not just monitored locations
- Looks at both construction projects which will produce PM2.5, and the extent to which future users of developments will be exposed to PM2.5
- Requires applicants to evidence:
- their consideration of key sources of air pollution within their schemes
- how they have taken appropriate action to minimise emissions of PM2.5 and its precursors ‘as far as is reasonably practicable’.
As a result, developments should mitigate from the design stage to ensure the minimum PM2.5 is emitted, and the minimum reasonably practicable exposure occurs, rather than showing that the development will not lead to an exceedance of a legal limit.
More Challenges
The focus on particulates raises some challenges for planners, who will have a new consideration to balance at site selection and design stage.
- For example, in looking at site proximity to pollution sources and the impact on future users of the site, planners may need to balance the sustainable transport and desirability benefits of well-connected sites on existing busy roads with access to bus routes and other public transport, but which may have potentially higher PM2.5 levels, due to the wearing of tyres and brakes on nearby roads.
- Presumably greenfield sites, away from existing development, are likely to experience lower levels of particulates, although may face other challenges in relation to sustainable transport, access to facilities and local and national policy designations which restrict development.
- What is the likely impact of greater consideration of particulates where an area previously focused on industrial processes gradually transitions to other uses, potentially introducing new residents and workers whilst some particulate producing operations are still taking place?
- Would strict consideration of the guidance make otherwise desirable seaside homes (subject to sea spray) or near agricultural fields or meadows (pollen) less suitable in planning terms?
- Should the PM2.5 exposure of future cyclists be considered when urban sites rely on new residents cycling rather than driving private cars to be acceptable in transport and parking terms?
- What effective mitigation measures are available to make outdoor amenity areas in existing PM2.5 level exceedance areas acceptable?
Looking at reducing PM2.5 exposure and emissions in site layout and development design will be an additional factor to balance in an already complex consideration of competing priorities.
Defra expects to publish a consultation on the new approach and full guidance in 2025. We await the publication of more detailed guidance to assist applicants and decision makers.
