Air Quality Targets in the Environment Act
This page summarises and provides links to publications relevant to the consultation on the PM2.5 targets being developed under the Environment Act 2021.
The Environment Act 2021 establishes a legally binding duty on government to bring forward at least two new air quality targets in secondary legislation by 31 October 2022. This duty sits within the environmental targets framework outlined in the Environment Act (Part 1).
The proposed air quality targets are:
- Annual Mean Concentration Target ('concentration target') - a maximum concentration of 10µg/m3 to be met across England by 2040
- Population Exposure Reduction Target ('exposure target') - a 35% reduction in population exposure by 2040 (compared to a base year of 2018).
We are seeking views on these targets as part of the Consultation on Environmental Targets. To respond to this consultation, please visit:
To support the development of the targets a comprehensive evidence programme was carried out, with external analysis and expert advice sought to inform the development of the target metrics, values and assessment approach. This work is detailed in the Defra evidence summary and the Defra evidence report. An impact assessment evaluating the benefits and economic costs of the targets is also provided. All of these documents are published alongside the consultation and can be accessed via the link above.
The external analysis and advice which feed into the evidence report are referenced as annexes to the report. These can be accessed via the links below:
Any views expressed within these documents are those of the authors, not Defra.
Air Quality Expert Group advice
Throughout the target development process, Defra have engaged closely with the Air Quality Expert Group (AQEG). Summaries of the advice they have provided are given below with links to the publications.
This note summarises discussions and advice following a workshop in November 2021 where the results of the modelling were presented to AQEG for scrutiny, views and comment. The note acknowledges the challenges associated with modelling PM2.5 and made some recommendations that were subsequently addressed and reflected in the modelling undertaken.
This note from May 2021 presents a summary of the uncertainties associated with monitoring PM2.5, and provides advice and recommendations particularly with regards to monitoring PM2.5 at the lower levels required to assess compliance of the new targets.
On 19 November 2020 AQEG launched a call for evidence on the modelling of future PM2.5 concentrations in order to inform their advice to Defra. This call sought evidence from the results of modelling as to the future concentration and composition in England, the main drivers of future changes, key modelling uncertainties and information relating to how population exposure might change.
From the responses received AQEG invited some respondents to present to them at an online workshop. AQEG produced a summary of what was learned from the call for evidence and made a number of recommendations to Defra. This information is informing the modelling approach being taken and provides context to the work, for example highlighting the technical complexities and uncertainties involved in air quality modelling.
- AQEG – Modelling of future PM2.5 in support of the Defra air quality target setting process
- Defra – Call for Evidence on future PM2.5 concentrations: Summary of responses and government response
A technical workshop was held with AQEG participation (but also wide expertise from across the air quality expert community) in September 2020. This workshop sought views on the metrics for PM2.5 targets and considered aspects such as the formulation, application and communication of metrics in order to develop effective targets. Notes prepared by the four participant groups on topics relating to metrics are provided.
In May 2020, early in the target development process, Defra asked AQEG for their initial views on a number of technical aspects relating to the proposed targets, and how they wished to be engaged in the target setting process. Following an online meeting with Defra, AQEG provided a summary note providing some preliminary advice.
Please note that this advice was provided at an early stage of the development process and some points may have been superseded or greater detail/qualification added at a later date. This initial advice helped to inform Defra’s early decision-making on areas such as metrics, measuring progress and modelling.
Committee on the Medical Effects of Air Pollutants
Defra have also requested advice from the Department of Health and Social Care’s expert advisory Committee on the Medical Effects of Air Pollutants (COMEAP) regarding the health evidence relevant to developing targets for PM2.5. The papers referenced below can be accessed via the COMEAP publications webpage.
This update to COMEAP’s advice was provided to Defra in light of the publication, in September 2021, of revised World Health Organization (WHO) Air Quality Guidelines. The guideline for annual mean concentrations of PM2.5 was updated to 5 µg/m3 (from 10 µg/m3). COMEAP’s update discusses the scientific evidence used in the derivation of the guideline.
Statement on quantifying mortality associated with long-term exposure to PM2.5 (2022)
This statement updates COMEAP’s recommendations for quantifying mortality associated with long-term exposure to PM2.5, based on COMEAP’s consideration of new scientific evidence. The recommended coefficient (concentration-response function, CRF) of relative risk (RR) = 1.08 per 10 µg/m3 PM2.5 is higher than the previous (2018) recommendation of RR = 1.06. per 10 µg/m3. The updated recommendation has been used in cost-benefit analyses of interventions to reduce PM2.5 concentrations, undertaken to inform the development of PM2.5 targets.
Statement on update of recommendations for quantifying hospital admissions associated with short-term exposures to air pollutants (2022)
This advice provides updated recommendations for quantifying respiratory and cardiovascular hospital admissions associated with exposure to particulate matter and NO2. It also reconfirms COMEAP’s previous recommendations for quantifying hospital admissions associated with exposure to ozone. The updated recommendations are intended to inform cost-benefit analyses of interventions to improve air quality.
Advice on health evidence relevant to setting PM2.5 targets (2021)
This note provides advice and recommendations based on the latest health evidence to inform our target setting. COMEAP were asked to provide advice addressing questions regarding the health evidence relevant to consideration of the development of targets for particulate air pollution. The questions concerned issues such as whether the proposed two-target approach, with both targets focused on reducing long-term exposure to PM2.5 was appropriate. The new evidence of effects at low concentrations, and the lack of evidence for a threshold for effects, is discussed. Questions regarding at-risk groups, and questions relevant to the metrics used to define targets, were also considered.
Early in the target development process Defra held a workshop with COMEAP to provide the committee with information on the target setting process and to obtain initial views on Defra’s proposed work programme, what aspects of the work programme the committee could provide advice on, and how they wished to be engaged in the target setting process. Following this online meeting with Defra, COMEAP provided a summary note providing some preliminary advice. Please note that this advice was provided at an early stage of the development process and some points may have been superseded or greater detail/discussion included in the more recent advice note(s).
Scenario Modelling Tool – Extending NAEI projection baseline to 2050 (Ricardo EE
This short report details how the National Atmospheric Emissions Inventory (NAEI) 2018 baseline emissions projections were extended from 2030 out to 2050 in the Scenario Modelling Tool (SMT). This work was undertaken by the current NAEI team at Ricardo EE.