An air quality assessment for a development project examines whether a proposed development could significantly affect local air quality, or whether existing pollution could affect people who will use or occupy the development.
For developers, architects and planning consultants, this often forms part of the supporting environmental information submitted with a planning application. The exact approach varies according to the location, scale and nature of the project. Some developments can be assessed relatively simply, while others require detailed computer modelling of pollutant concentrations.
Importantly, an air quality assessment does not automatically mean installing monitoring equipment at the site. For many development projects, existing information combined with established modelling techniques provides the evidence required to assess potential effects.
UK planning guidance emphasises that the level of assessment should be proportionate to the nature and scale of the development, its location and the potential air quality effects.
When does a development need an air quality assessment?
Not every planning application requires a detailed air quality study.
The first stage is normally to establish whether air quality could be a material consideration for the proposed development. This depends both on what the development will introduce and on the environmental conditions surrounding the site.
An assessment may be appropriate where a proposal could generate a significant change in road traffic, introduce new emissions, place new sensitive uses in an area of poorer air quality, or involve construction works where dust could require consideration.
Location is particularly important. A proposed development close to busy roads or within or near an Air Quality Management Area may require greater scrutiny than an equivalent scheme in an area where pollutant concentrations are comfortably below relevant objectives.
The appropriate scope should therefore be established for the individual development rather than applying the same methodology to every project.
Guidance from the Institute of Air Quality Management (IAQM) and Environmental Protection UK provides a framework for considering air quality within the planning and development control process. The guidance is intended to help ensure that the assessment undertaken is appropriate to the potential impacts of the development.
What information is collected before the assessment begins?
An effective assessment starts with understanding the proposed development and its surroundings.
The consultant will normally review the site location, development proposals and planning context before deciding what level of assessment is necessary. Information may include the proposed number and type of residential or commercial units, site access arrangements, expected traffic movements and the location of nearby roads and sensitive receptors.
Existing environmental information is also important.
This can include:
- local authority air quality information, nearby monitoring results, Air Quality Management Areas and relevant background pollutant concentrations
- development plans, traffic information, proposed site layouts and the position of existing and proposed sensitive receptors
The purpose is to create an appropriate baseline against which the potential effects of the development can be assessed.
A good site layout can also matter. The distance between buildings and significant roads, the positioning of residential accommodation and the location of ventilation points may influence how potential exposure is considered.
How is the scope of the assessment decided?
Once the initial information has been reviewed, the environmental consultant determines the most proportionate assessment method.
For a relatively small proposal in an area with good existing air quality, detailed dispersion modelling may not always be justified. A screening or qualitative assessment may provide sufficient evidence.
More complex developments may require detailed quantitative modelling.
The decision will depend on factors such as existing pollutant concentrations, anticipated changes in traffic, the sensitivity of surrounding land uses and whether the development introduces new receptors into a potentially constrained location.
National planning guidance specifically states that assessments should be proportionate to the proposed development and potential impact. It also recommends discussing the scope of supporting information between the applicant and local planning authority before it is commissioned where appropriate.
This early scoping process can prevent unnecessary work while ensuring that material air quality issues are addressed properly.
How is air quality modelling used in a planning assessment?
Where a detailed assessment is necessary, dispersion modelling can be used to estimate pollutant concentrations at specific locations.
Rather than simply measuring conditions at one moment in time, modelling can examine different scenarios. Typically, this allows the consultant to consider existing or future conditions without the development and compare them with conditions once the proposed development is in place.
For road traffic assessments, the model may incorporate information such as traffic flows, vehicle composition, road characteristics, meteorological conditions, background pollution and the position of nearby buildings or receptors where relevant.
Potential receptors could include existing homes close to roads affected by development traffic or proposed residential accommodation within the development itself.
The modelling then estimates pollutant concentrations at these representative locations.
The important question is not merely whether there is a numerical change. The consultant must interpret the results in the context of relevant air quality objectives, existing conditions and accepted assessment guidance.
Does an air quality assessment always require on-site monitoring?
No. This is an important distinction for development projects.
Air quality assessments are sometimes assumed to involve installing monitoring equipment and collecting measurements from the development site. In planning work, however, on-site monitoring is often unnecessary.
A large amount of information may already be available from local authority monitoring networks, national datasets and other reliable sources. When suitable information is available, it can be used alongside modelling to establish representative baseline conditions.
Where project-specific monitoring genuinely is necessary, it needs to be planned appropriately. Hawkins Environmental’s experience is that meaningful on-site air quality monitoring generally requires a substantially longer period than a few weeks, commonly at least three to six months.
For this reason, identifying whether monitoring is actually required at an early stage can have significant implications for a development programme.
Developers should therefore avoid assuming that an air quality assessment and an air quality monitoring exercise are the same thing. They serve different purposes, and the appropriate approach depends on the evidence needed for the planning application.
What about dust during construction?
For developments involving demolition, earthworks or substantial construction activity, the assessment may also consider the risk of dust and particulate effects during the construction phase.
This is generally assessed differently from long-term operational air quality.
Factors such as the scale of the works, the nature of the activities, the distance to nearby sensitive receptors and the effectiveness of proposed mitigation measures can all influence the level of risk.
IAQM guidance provides an established approach to assessing dust associated with demolition and construction, with the emphasis placed on determining the level of risk and identifying appropriate mitigation.
Measures could include appropriate site management, controlling dust-generating activities, managing vehicle movements and maintaining suitable procedures during particularly dusty work.
The aim is to identify proportionate controls based on the actual risk presented by the project.
How are the results interpreted?
Running a computer model is only one part of the assessment.
The results must be reviewed by an experienced consultant who can explain what the predicted concentrations and changes mean in planning terms.
This may involve considering whether relevant air quality objectives are likely to be met at sensitive receptors and assessing the significance of changes associated with the proposed development.
An assessment may find that the development is unlikely to create a significant air quality effect. In other cases, it might identify parts of the scheme where design changes or mitigation should be considered.
The resulting report should clearly explain the methodology, assumptions, data sources, results and conclusions so that planners and environmental health officers can understand how the findings were reached.
The objective is not simply to produce a collection of modelling outputs. It is to provide evidence that allows the environmental effects of a development to be considered properly within the planning process.
Can the assessment influence the development design?
Yes, and this is one reason why considering air quality early can be beneficial.
If potential issues are identified while a scheme is still being designed, the project team may have more opportunities to respond.
For example, the layout could potentially be adjusted so that sensitive parts of a development are positioned away from the most significant pollution sources. Changes to access arrangements or other aspects of the proposal may also be considered where appropriate.
For larger projects, air quality should ideally be viewed as part of the wider design and planning process rather than as an isolated report commissioned shortly before submission.
Developers requiring several forms of technical environmental evidence can review Hawkins Environmental’s environmental services to understand how assessments can support the wider planning process.
What happens after the air quality assessment is completed?
Once the assessment has been completed, the findings are normally presented in an air quality report suitable for submission with the planning application.
The report should provide enough information for the relevant planning and environmental health teams to understand the project, assessment methodology, baseline conditions, predicted effects and any proposed mitigation.
Depending on the project, the consultant may also need to respond to technical queries raised during determination.
Early communication can be valuable here. If the scope and assumptions are appropriate from the beginning, it reduces the risk that significant additional work will be requested once an application is already being considered.
This does not guarantee that there will be no questions or objections. Planning decisions involve many considerations, and individual authorities may require project-specific information. It does, however, help provide a clear technical basis for consideration of air quality.
When should air quality consultants become involved?
For potentially sensitive projects, earlier is generally better.
Waiting until the planning application is almost ready to submit can leave limited opportunity to respond if a potential constraint is identified. It can be particularly problematic if project-specific monitoring proves necessary because meaningful data cannot normally be collected retrospectively at short notice.
Bringing an environmental consultant into the project during feasibility or design development allows time to identify likely requirements, agree the appropriate scope and highlight issues that could influence the design.
For straightforward developments, early advice may also establish that only a proportionate assessment is needed, avoiding unnecessary work.
Frequently Asked Questions
How long does an air quality assessment take?
Timescales depend on the complexity of the development, availability of traffic and environmental data, whether detailed dispersion modelling is required and whether additional information must be obtained. Developers should seek advice early where air quality may be a planning consideration.
Can an air quality assessment be completed without monitoring?
Yes. Many planning-related air quality assessments can use existing monitoring information, background datasets and dispersion modelling without requiring new on-site monitoring. The appropriate methodology depends on the site and development.
Who reviews an air quality assessment submitted with planning?
The local planning authority will consider the information submitted with the application and may seek technical input from relevant environmental health officers or other consultees. A clear methodology and transparent reporting make it easier for reviewers to understand the basis for the assessment.
A proportionate approach to air quality and development
An air quality assessment is not a standardised test carried out in exactly the same way for every development. It is a proportionate technical assessment designed around the project, its location and the environmental issues that could materially affect the planning decision.
The process normally begins with screening and baseline review, followed by detailed modelling where justified. The findings are then interpreted against relevant guidance and objectives, with mitigation or design recommendations provided where necessary.
Crucially, detailed assessment should not be confused with routine on-site air quality monitoring. For most projects handled by Hawkins Environmental, monitoring is not required, and appropriate modelling and existing evidence can instead be used to support the planning process.
For authoritative industry guidance on planning-related assessments, developers and project teams can also refer to the urlIAQM guidance libraryhttps://iaqm.co.uk/guidance/.
If you are planning a development and need to establish whether an air quality assessment is required, Hawkins Environmental can provide proportionate advice and assessment support for planning applications. You can also contact Hawkins Environmental to discuss the proposed development and likely assessment requirements.
Phone: 01256 522332
Email: enquiry@hawkinsenvironmental.co.uk
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