HEI-funded research played important role in European Union’s adoption of new air quality standards to improve public health

The Health Effects Institute (HEI) acknowledges the formal adoption of the European Union’s (EU) revised Ambient Air Quality Directive (AAQD). The revised AAQD sets new air quality standards for EU countries to achieve by 2030 for major pollutants to align more closely with the latest World Health Organization (WHO) guidelines. In particular, the new annual limit values of 10 µg/m³ for fine particulate matter (PM_2.5) and 20 µg/m³ for nitrogen dioxide (NO₂) will provide important benefits to public health. The legislation also includes strengthened monitoring and measuring provisions for air pollution, and rules for access to justice and compensation for people whose health has been impacted by air pollution. The outcome of this week’s vote is the result of a multiyear process to revise the AAQD, which has remained unchanged since 2008. EU member states will have two years to transpose the EU text into their national laws.

Air pollution is the top environmental risk to health in Europe. Everyone is vulnerable to its impacts, with some at greater risk than others. Levels of vulnerability are often outside of individual control, and can evolve with age, health condition, and socioeconomic status, as well as where people live, study, or work.

Although much progress has been made and ambient air pollution continues to decline in high-income regions, epidemiological studies have found health effects at levels below current standards. HEI recently completed a comprehensive research initiative to investigate the health effects of long-term exposure to low levels of air pollution in Europe, Canada, and the United States. Particular strengths of the studies included the unprecedentedly large populations (7–69 million people), state-of-the-art exposure assessment methods, and thorough statistical analyses that applied novel methods.

All three of HEI’s low-level exposure studies documented positive associations between mortality and exposure to PM_2.5 below the current EU limit values and the US National Ambient Air Quality Standards (NAAQS). Furthermore, the studies documented linear (US), or supra-linear (Canada and Europe) exposure-response functions between PM_2.5 and mortality, with no evidence for a threshold. A supra-linear function indicates a larger relative effect per additional unit of exposure at low pollutant concentrations than at high concentrations. Together, the research, which was subjected to rigorous HEI peer review, provided important new evidence of the adverse health effects of long-term exposures to low levels of air pollution at and below current standards, suggesting that further reductions could yield larger benefits than previously anticipated. Based on these and other studies, WHO released new Air Quality Guidelines in September 2021. It recommended that annual mean concentrations of PM_2.5 and NO₂ should not exceed 5 and 10 μg/m³, noting that adverse health effects were documented to occur above these values.

These findings on low-level exposure, particularly those from the HEI-funded ELAPSE (Effects of Low-Level Air Pollution: A Study in Europe) study of 28 million participants, played an important role in informing the new EU air quality standards. Of note, findings from the ELAPSE study were used by the European Commission to estimate the influence of the choice of the exposure–response function on mortality in the accompanying impact assessment. The use of ELAPSE resulted in higher attributable mortality estimates, indicating that the current health burden of air pollution may be underestimated in Europe.

The full reports of all three studies, including a wide range of sensitivity analyses conducted by each team and the Commentaries of the HEI Review Panel, can be found at the Health Effects Institute website. HEI has also recently published a journal paper synthesizing the results, the strengths and limitations of the research, and remaining research needs. References are available below.

Contact: Hanna Boogaard, jboogaard@healtheffects.org
 
HEI’s Low-Level Exposure Studies
1.    EUROPE: Mortality and Morbidity Effects of Long-Term Exposure to Low-Level PM_2.5, BC, NO₂, and O₃: An Analysis of European Cohorts in the ELAPSE Project
2.    US: Assessing Adverse Health Effects of Long-Term Exposure to Low Levels of Ambient Air Pollution: Implementation of Causal Inference Methods
3.    CANADA: Mortality–Air Pollution Associations in Low-Exposure Environments (MAPLE): Phase 2

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References

Boogaard H, Crouse DL, Tanner E, Mantus E, van Erp AM, Vedal S, Samet J. Assessing Adverse Health Effects of Long-Term Exposure to Low Levels of Ambient Air Pollution: The HEI Experience and What's Next? Environ Sci Technol. 2024;58:12767-12783.

Brauer M, Brook JR, Christidis T, Chu Y, Crouse DL, Erickson A, et al. 2019. Mortality–Air Pollution Associations in Low-Exposure Environments (MAPLE): Phase 1. Research Report 203. Boston, MA: Health Effects Institute.

Brauer M, Brook JR, Christidis T, Chu Y, Crouse DL, Erickson A, et al. 2022. Mortality–Air Pollution Associations in Low Exposure Environments (MAPLE): Phase 2. Research Report 212. Boston, MA: Health Effects Institute.

Brunekreef B, Strak M, Chen J, Andersen ZJ, Atkinson R, Bauwelinck M, et al. 2021. Mortality and Morbidity Effects of Long-Term Exposure to Low-Level PM_2.5, BC, NO₂, and O₃: An Analysis of European Cohorts in the ELAPSE Project. Research Report 208. Boston, MA: Health Effects Institute.

Dominici F, Schwartz J, Di Q, Braun D, Choirat C. Zanobetti A. 2019. Assessing Adverse Health Effects of Long-Term Exposure to Low Levels of Ambient Air Pollution: Phase 1. Research Report 200. Boston, MA: Health Effects Institute.

Dominici F, Zanobetti A, Schwartz J, Braun D, Sabath B, Wu X. 2022. Assessing Adverse Health Effects of Long-Term Exposure to Low Levels of Ambient Air Pollution: Implementation of Causal Inference Methods. Research Report 211. Boston, MA: Health Effects Institute.

European Commission (EC). Proposal for a Directive of the European Parliament of the Council on Ambient Air Quality and Cleaner Air for Europe. COM/2022/542 final.

European Commission (EC) Staff Working Document. Impact Assessment Report. Accompanying the Document Proposal for a Directive of the European Parliament and of the Council on Ambient Air Quality and Cleaner Air for Europe (recast). SWD/2022/545 final.

Hoffmann B, Brunekreef B, Andersen ZJ, Forastiere F, Boogaard H. Benefits of future clean air policies in Europe. Proposed analyses of the mortality impacts of PM_2.5 and NO₂. Environ Epidemiol 2022;6:e221.

World Health Organization. WHO global air quality guidelines: Particulate matter (PM_2.5 and PM₁₀), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. Geneva: World Health Organization. 2021.