Assessing air quality impacts as part of your planning application

Air quality impacts from or associated with proposed developments have the potential to damage important features of protected sites.

This advice sets out when we expect you to consider potential effects on protected sites as part of your planning application, and what supporting information is required.

Protected sites include:

• Special Areas of Conservation (SAC)
• Special Protection Areas (SPA)
• Ramsar Sites
• Sites of Special Scientific Interest (SSSI)
• National Nature Reserves (NNR)
• Marine Conservation Zones (MCZ)
  
  

When to consider potential air quality impacts on protected sites 

Agricultural developments

Air quality impacts from increases in traffic movements

If your proposed development increases traffic movements, and; 

• There are protected sites within 200m of the edge of a road, from which your proposed development will generate additional traffic, and;

• The increase in annual average daily traffic (AADT) flow from the development (either alone or in-combination with other plans or projects) is greater than 1000 light duty vehicles or 200 heavy duty vehicles. 

Then there is potential for unacceptable air quality impacts upon protected sites, and you will need to prepare an Air Quality Assessment of the potential impacts in support of your planning application. 

Air quality impacts from dust emitting activities

If your proposed development involves a dust generating construction activity, and there are protected sites within: 

• 50m of the application site boundary, or;

• 50m of the route(s) used by construction vehicles on the public highway, within a 500m radius of the application site entrance(s), and/ or; 

If your proposed development proposes a mineral extraction activity, and there are protected sites within: 

• 250m of the application site for soft rock mineral sites (e.g., sand and gravel), and; 

• 400m of the application site boundary for hard rock mineral sites (e.g., granite).

Then there is potential for unacceptable air quality impacts upon protected sites and you will need to prepare an Air Quality Assessment of the potential impacts in support of your planning application. 

Air quality impacts from installations

If your proposed development involves an installation and falls within the relevant screening distances, aerial emissions have the potential to impact protected sites. In such cases your planning application should be supported by an Air Quality Assessment. If you do not carry out an Air Quality Assessment, we may object to your planning application.

You can establish the location of protected sites, in relation to your proposed development site on the Data Map Wales website.

Standard screening distances

Check if there are any of the following within 10 km of your application site:

• SACs
• SPAs
• Ramsar sites

Check if there are any of the following within 2 km of your application site:

• SSSIs
• MCZs
• NNRs

Exceptions and adjustments

Apply the following where relevant:

• Use a 15 km screening distance for all designated sites where your proposed development involves:

• Natural gas-fired combustion plant >500 MW (th)
• Sulphurous fuel combustion plant >50 MW (th)

• Use a 0.5 km screening distance for all designated sites where the MW (th) from the proposed development is 0.5 to <1 when using non-sulphurous fuel, and a 1 km screening distance when sulphurous fuel is used.
  
  
• No screening of designated sites is required where the MW (th) from your proposed development is <0.5, unless the development is located within the boundary of a designated site.
  
  
• Where it is known that a Medium Combustion Plant (MCP) permit will be required, you should apply the relevant screening distances set out in NRW's MCP guidance. Where it is not clear whether an MCP permit will be required, you should adopt the standard screening distances above.

Please note, where NRW’s MCP guidance does not include screening distances for NNRs, the screening distances for SSSIs should be used instead.

What to include in your Air Quality Assessment

After you have identified any protected sites, you will need to prepare an Air Quality Assessment of the potential impacts in support of your planning application to account for increases in traffic movements and any installation activities.

Your assessment should identify the site relevant critical levels (CLe) and site relevant critical loads (CLo), to the qualifying features of protected sites within the screening distances set out in the table above.

You can find information on CLe and CLo on the Air Pollution Information System (APIS) website.

Should no information be available on APIS for the identified protected site, then you should use the CLe and CLo thresholds outlined in Air emissions risk assessment for your environmental permit on GOV.UK, specifically the section titled ‘Screening for protected conservation areas’.

To establish whether your proposed development may have a significant impact on a protected site you must consider its process contribution (PC). No further assessment of air quality impacts is required if: 

When the PC from your proposed development is >1% of the CLe and/ or Clo of the protected site, the next stage of your assessment should calculate the predicted environmental concentration (PEC). PEC is the PC from your proposed development plus the existing background level of a pollutant currently at the protected site.

You should refer to Air emissions risk assessment for your environmental permit for guidance on assessing PEC, and the next steps to undertake for any PECs not screened out as insignificant.

Following calculation of the PEC, if you have determined that your proposed development has potential to cause a ‘Likely Significant Effect’ (LSE) on a protected site, then further assessment is required.

Where PECs exceed the relevant assessment criteria and the PC is not insignificant, you will need to undertake further assessment of potential impacts and/ or propose mitigation measures, to ensure there will be no adverse effects.

Any dust emitting activities should also be accounted for by producing a Dust Impact Risk Assessment and Dust Management Plan or Construction Environmental Management Plan (CEMP), containing appropriate dust suppression and mitigation measures.

These documents should assess the risk of significant effect on sensitive species and habitat features. This assessment may be a standalone document or incorporated as a section or chapter in an overarching Air Quality Assessment.

Further advice

If you require further advice about air quality impacts when preparing your planning application, visit Our service to developers which sets out how you can obtain advice from us before submitting your planning application to your Local Authority. 

Contact us to check if you need other licences, consents, approvals or permissions. There may be a charge for this service.