An air quality assessment considers the pollutants most likely to affect a proposed development, nearby residents, existing land uses and local air quality objectives. In planning terms, the assessment is not simply a generic review of “air pollution”. It is a focused technical report that looks at the relevant pollutant sources, sensitive receptors and likely impacts associated with a specific site.
For many developments, the main pollutants considered are nitrogen dioxide, PM10 and PM2.5. These are commonly linked to road traffic, heating plant, energy centres, construction activity and existing sources close to the site. However, the exact scope depends on the development type, location, local authority requirements and whether the site is introducing new people into an area already affected by poor air quality.
For architects, planning consultants, developers and design teams, understanding which pollutants are relevant can help prevent delays, reduce uncertainty and support a stronger planning submission.
Why Are Pollutants Assessed During Planning?
Pollutants are assessed because new development can both affect local air quality and be affected by existing air quality conditions.
A development may increase traffic, introduce new combustion plant, generate construction dust or change the way people are exposed to pollution. Equally, a proposed residential scheme, school, care facility or mixed-use development may place future occupants close to a busy road, junction, industrial activity or other local source.
Planning authorities use air quality information to decide whether a proposal is acceptable, whether mitigation is needed and whether the development aligns with local and national environmental policy. An air quality assessment can also help demonstrate that the design team has considered air quality early enough to avoid avoidable problems later in the application process.
The assessment usually considers two broad questions:
- Will the development make air quality worse for existing receptors?
- Will future occupants of the development be exposed to unacceptable air quality?
The answer depends on the pollutants involved, the sensitivity of nearby receptors and the scale of the predicted effect.
What Are the Main Pollutants in an Air Quality Assessment?
The pollutants considered in an air quality assessment vary depending on the site, but several pollutants are especially common in planning work.
Nitrogen dioxide
Nitrogen dioxide, often shortened to NO2, is one of the most frequently assessed pollutants for planning applications. It is strongly associated with road traffic emissions, particularly from diesel vehicles, and can be an important consideration near busy roads, junctions, bus routes and town centre locations.
For development sites close to existing roads, an assessment may consider whether future residents, workers or other users could be exposed to elevated NO2 levels. For developments expected to increase traffic, it may also consider whether additional vehicle movements could affect existing homes, schools or other sensitive locations nearby.
NO2 is often central to air quality assessments in urban and roadside environments because it is closely linked with local traffic conditions and Air Quality Management Areas.
PM10
PM10 refers to particulate matter with a diameter of 10 micrometres or smaller. These particles can come from a range of sources, including road traffic, brake and tyre wear, construction activity, demolition works, combustion processes and some industrial activities.
In planning assessments, PM10 may be considered during both the construction and operational phases of a development. During construction, the concern is often dust and particulate emissions from demolition, earthworks, trackout and site machinery. During operation, the concern may relate to traffic, plant or nearby existing sources.
Because PM10 can be relevant to both nuisance dust and health-related exposure, it is often considered alongside dust soiling and PM2.5.
PM2.5
PM2.5 refers to fine particulate matter with a diameter of 2.5 micrometres or smaller. These smaller particles can remain airborne for longer and are an important pollutant in public health and planning discussions.
In many air quality assessments, PM2.5 is considered alongside PM10 and NO2, particularly where road traffic, combustion plant or background air quality levels are relevant. For planning purposes, PM2.5 can be especially important where a development introduces sensitive receptors such as residential occupants, children, older people or people with existing health vulnerabilities.
Assessment requirements may also depend on local authority policy, local air quality conditions and whether the site is in an area where particulate matter is already a concern.
Is Construction Dust Considered a Pollutant?
Construction dust is often considered within an air quality assessment, especially where a development involves demolition, earthworks, construction traffic or works close to homes, schools, offices or public spaces.
Construction dust is not assessed in exactly the same way as long-term traffic-related pollution. Instead, the assessment usually considers the risk of dust soiling, human health effects from particulate matter and the sensitivity of the surrounding area. The level of risk depends on factors such as the scale of works, distance to receptors, site conditions and the types of activity proposed.
Typical construction-phase considerations include:
- demolition dust
- earthworks and soil movement
- construction vehicle trackout
- dust from cutting, crushing or material handling
- particulate emissions from construction machinery
Where construction dust risk is identified, the assessment may recommend practical mitigation measures. These can include dust management procedures, wheel washing, damping down, site hoarding, covering loads and good site management practices.
For many planning applications, this is not about continuous long-term monitoring. It is more often about assessing the likely risk and setting out proportionate controls so construction impacts can be managed responsibly.
Are Odour Impacts Included?
Odour may be considered when a proposed development is close to an existing odour source or when the development itself could introduce an odour-generating activity.
Examples might include sites near wastewater treatment works, commercial kitchens, agricultural uses, waste handling operations, industrial processes or certain manufacturing activities. Odour can be particularly important when new residential development is proposed close to an existing business or facility that already operates lawfully.
In this situation, the planning issue is not only whether odour could affect future occupants. It may also be whether the new development could create future complaints that restrict an existing operation. This is why odour can become an important compatibility issue in mixed-use and edge-of-industrial locations.
Odour is not included in every air quality assessment. It is usually scoped in where there is a clear source, pathway and receptor relationship.
Are Combustion Emissions Considered?
Combustion emissions may be considered where a development includes boilers, combined heat and power units, generators, biomass plant, energy centres or similar equipment.
The relevance depends on the type, size, fuel, operating profile and location of the plant. For example, a small domestic-style heating system may not require detailed consideration in the same way as a larger energy centre serving a major mixed-use scheme.
Where combustion plant is relevant, the assessment may consider emissions such as nitrogen oxides and particulate matter. It may also review flue height, dispersion, nearby building effects and the proximity of sensitive receptors.
This is particularly important in dense urban areas where buildings can affect how emissions disperse, or where the site is already close to air quality objective levels.
Are Industrial Pollutants Considered?
Industrial pollutants may be considered when a development is close to existing industrial activity or where the proposed use could introduce emissions.
The specific pollutants depend on the source. For example, one site might need to consider dust from a quarry or minerals operation, while another might need to consider emissions from a manufacturing process, energy facility or commercial operation.
For most standard residential or commercial planning applications, the main pollutants remain NO2, PM10 and PM2.5. However, where the local context is more complex, the assessment may need to consider additional pollutants or sources.
This is why scoping is important. A good assessment should not include irrelevant pollutants for the sake of appearing comprehensive. It should focus on the pollutants that genuinely matter for the site and planning decision.
Does Every Assessment Consider the Same Pollutants?
No. Every air quality assessment should be proportionate to the development and its setting.
A small development on a quiet site may only need a brief review, especially if it is not expected to increase traffic materially and is not located near a source of poor air quality. A larger residential scheme near a congested road, an Air Quality Management Area or a sensitive existing use may need a more detailed assessment.
The pollutants considered are influenced by several factors, including the type of development, the planning authority’s requirements, traffic generation, local background concentrations, nearby industrial or commercial sources, construction activity and whether sensitive receptors are present.
This is why early advice can be useful. It helps the project team understand whether a full air quality assessment is required, what pollutants should be included and whether any design changes or mitigation measures may be needed before submission.
How Do Pollutant Findings Affect Planning Decisions?
Pollutant findings help planning officers and environmental health teams understand whether a development is acceptable in air quality terms.
If the assessment shows that pollutant levels are acceptable and the development is unlikely to create a significant effect, the report can support the application by addressing air quality concerns clearly. If potential issues are identified, the assessment may recommend mitigation.
Mitigation could include design changes, mechanical ventilation strategies, relocating sensitive uses away from pollution sources, reducing emissions from plant, improving construction dust controls or supporting low-emission travel measures.
In some cases, air quality findings can affect the layout and design of a scheme. For example, bedrooms, balconies or fresh air intakes may need careful positioning if a site is close to a busy road. In other cases, the main requirement may be a construction dust management approach or further technical justification.
The key point is that pollutant findings are not just technical details. They can influence design, planning conditions, consultation responses and the confidence of the local planning authority.
How Can Developers Prepare for an Air Quality Assessment?
Developers and design teams can make the process smoother by considering air quality early. This is particularly important where the site is close to traffic, in or near an Air Quality Management Area, involves sensitive uses or may generate additional vehicle movements.
Useful early information includes the site address, proposed use, number of dwellings or floorspace, expected vehicle trips, construction details, nearby roads, proposed plant and any local authority comments. If pre-application advice has already mentioned air quality, that should also be reviewed carefully.
Early assessment can help identify whether the key concern is exposure, emissions, construction dust, odour, operational plant or a combination of these. It can also help avoid late design changes once the planning application is already under review.
For related support, Hawkins Environmental’s services page outlines the environmental planning assessments available for development projects. If you need site-specific advice, the contact page is the most direct next step.
Frequently Asked Questions
What pollutants are usually included in an air quality assessment?
The most commonly assessed pollutants are nitrogen dioxide, PM10 and PM2.5. Construction dust may also be assessed where demolition, earthworks or construction activity could affect nearby receptors. Other pollutants, odour or industrial sources may be included if they are relevant to the specific site.
Is air quality monitoring always required?
No. For many planning applications, an air quality assessment is based on desk-based review, modelling, local authority data and professional judgement. Monitoring may be required in some circumstances, but it is not automatically needed for every project.
Why is nitrogen dioxide important in planning?
Nitrogen dioxide is closely linked with road traffic emissions and is often a key concern near busy roads, junctions and Air Quality Management Areas. It can influence whether a site is suitable for sensitive uses such as housing, schools or care facilities.
Can construction dust affect a planning application?
Yes. Construction dust can be a planning concern where works are close to existing homes, workplaces, schools or public areas. The issue is often managed through a dust risk assessment and practical mitigation measures rather than becoming a reason to refuse development.
When should air quality be considered in the design process?
Air quality should be considered as early as possible, especially for sites near busy roads, industrial sources or areas with known air quality issues. Early consideration can help shape layout, ventilation, mitigation and planning strategy before the application is submitted.
Summary
An air quality assessment considers the pollutants that are relevant to a specific development and its surroundings. In many planning cases, this means nitrogen dioxide, PM10 and PM2.5, with construction dust also considered where works could affect nearby receptors. In more complex settings, odour, combustion emissions or industrial sources may also need to be reviewed.
The purpose is not to assess every possible pollutant. It is to identify the pollutants that matter, understand their likely effect and provide clear evidence for the planning authority. A proportionate, well-scoped assessment can help avoid delays, inform design decisions and support a more robust planning application.
For further background on UK air pollutants and policy context, Defra’s UK Air information provides a useful overview.
If your development may require an air quality assessment, Hawkins Environmental can provide practical, planning-focused advice based on the site, proposal and local authority requirements.
Phone: 01256 522332
Email: enquiry@hawkinsenvironmental.co.uk
Find out more: https://hawkinsenvironmental.co.uk/
