Assess air quality impacts
Techniques that analysts, consultants and academics can use to assess the effect of air pollution on human health and the environment.
Documents
Details
Email igcb@defra.gov.uk for:
- feedback on this guidance page and how you have used it for your appraisal
- help with deciding which approach to use in your appraisal
- help using the damage costs toolkit or a request for the toolkit in an accessible format
Understanding the impacts of air pollution
This guidance details the process for assessing the impact on air quality of a policy. You should consider the impact of air pollution in policy making and appraisal where there is potential for air quality impacts, including where polices indirectly result in changes in emissions.
The quality of the air can have an impact on:
- human health and wellbeing
- productivity
- the environment
In 2019, the mortality burden of the air pollution mixture (based on both particulate matter (PM2.5) and nitrogen dioxide (NO2)) in the UK, was equivalent to 29,000 to 43,000 deaths at typical ages. (Source: Chemical hazards and poisons report: issue 28).
In 2019, air pollution was estimated to have an economic cost of £27 billion per year in core healthcare costs and productivity losses with the estimates increasing to as much as £50 billion when wider impacts, such as dementia, are accounted for. (Source: rcp summary for policymakers a breath of fresh air responding to the health challenges of modern air pollution).
Ground-level ozone contributes to environmental harm. In a typical year, ozone reduces crop yields of wheat, potatoes and oilseed rape by approximately 5%. (Source: International Cooperative Programme on Effects of Air Pollution on Natural Vegetation and Crops 2014 to 2017).
National air quality objectives and limits
Concentrations of a range of pollutants in ambient air are regulated by the Air Quality Standards Regulations (AQSR) (2010). The AQSR (2010) set ‘limit values’, ‘target values’, ‘long-term objectives’ and ‘critical levels’ for ambient concentrations of pollutants. For more information go to Air pollution in the UK 2024: compliance assessment summary.
In addition, concentrations of fine particulate matter are regulated by more recent legislation which came into force in January 2023: the Environmental Targets (Fine Particulate Matter) (England) Regulations 2023 (UK Government, 2023).
Consider whether your policies are likely to result in a breach of any regulations. If they are, take mitigating action to prevent a breach and also assess the impact of the breach using this guidance.
Consider appropriate abatement measures and understand the potential costs involved, including whether there are local issues to take into account. If you need help quantifying abatement measures, email Defra igcb@defra.gov.uk.
Further information:
- for guidance about general appraisal methodology, go to the HM Treasury Green Book
- for information about the application of this guidance for transport policies, go to DfT’s Transport Appraisal Guidance (TAG), specifically the TAG data book Table A3.2 (TAG data book - GOV.UK) and Section 3 of the TAG unit A3 environmental impact appraisal (Tag unit A3 environmental impact appraisal)
- for data on the ‘activity costs’, go to DESNZ’s Green Book supplementary guidance: valuation of energy use and greenhouse gas emissions for appraisal. Specifically Table 14 and Table 15 of the data tables (data-tables-1-19.xlsx)
- for a detailed report on the damage costs update, go to the 2025 damage cost report
Updates to this page
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Updated the html attachments, damage costs toolkit and added a flowchart.
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Corrected the figure for the high value for PM2.5 for rail transport inner London on table 10 of "Air quality appraisal: damage cost guidance". This value is £1,109,872.
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On the damage cost guidance - changed the mortality burden of air pollution mixture from '28,000 to 36,000' to '29,000 to 43,000'.
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Updates made to the information and data on 'Air quality appraisal: damage cost guidance' and 'Air quality appraisal: impact pathways approach' and uploaded an updated version of 'Air quality appraisal: damage costs toolkit'. The format of some of the tables have also been changed to make them easier to read.
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Air quality damage cost appraisal toolkit updated.
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Updated '2019' to '2020' in these instances: Annex A: updated 2020 damage costs. Introduction: 2020 damage costs. 1.1 Title Table 1: 2020 damage cost values …appraisal period starts in 2020 …should first be uplifted to 2020. Changed '2021' to '2022' in Section 3.1 after "tonnes per year".
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Values in Table 8 'contribution of different impact pathways to overall national damage costs' in impact pathway guidance publication updated.
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New air quality appraisal toolkit. Updated damage cost guidance with new values in these tables and steps, now showing 2020 to 2029 instead of 2019 to 2028: Table 1: 2020 damage cost values Table 3: level of change in NOx emissions Table 4: change in emissions (t) with appropriate damage cost (£) Table 5: change in emissions, appropriate damage cost and rebased damage cost Table 6: annual uplift factors being applied to the rebased damage costs Table 7: calculating the total annual benefit of the change in emissions Step 6: discount benefits across the period of the policy appraisal to calculate total present value Table 8: total benefits of the change in emissions Step 7: sensitivity analysis Table 9: total discounted benefits - high sensitivity Table 10: updated full set of damage costs
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First published.