Air pollution is a global public health issue. According to the WHO, approximately 7 million premature deaths each year are attributed to the effects of air pollution, with more than 4 million linked to outdoor air pollution. A comprehensive review of the literature from the past 15 years led the World Health Organization (WHO) to publish new guidelines for ambient air quality that are significantly lower and more stringent than those published in 2005. A press conference is being streamed live on WHO’s social media channels: Facebook; Twitter; YouTube; Instagram.

WHO Literature Review: Key Takeaways

• Air pollution causes respiratory and cardiovascular effects that can lead to premature death. It also contributes to the development of diseases such as diabetes and neurodegenerative diseases, and it affects children’s health from a very young age. In 2013, outdoor air pollution was classified as a carcinogen by the International Agency for Research on Cancer (IARC).

• Health effects occur at any level of pollution, as shown by the ELAPSE report for Europe.

• Certain air pollutants—particularly black carbon (a component of particulate matter) and tropospheric ozone—contribute to climate change. Consequently, the gradual reduction in the use of fossil fuels and biomass would lower greenhouse gas emissions as well as concentrations of pollutants that impact health. The WHO therefore urges the promotion of a sustainable economic recovery following the gradual lifting of restrictions related to the COVID-19 pandemic, ensuring both improved air quality and climate change mitigation.

Stricter reference thresholds to reduce the health impacts of ambient air pollution

The new WHO guidelines propose reference thresholds¹ and interim targets² for particulate matter (PM2.5 and PM10), nitrogen dioxide (NO₂), ozone (O₃), sulfur dioxide (SO₂), and carbon monoxide (CO). They also provide qualitative information on best practices³ for managing certain types of particulate matter for which there is insufficient quantitative data to establish reference thresholds.

WHO reference thresholds recommended in 2021 compared to those in the 2005 air quality guidelines

Sources:
WHO 2006, Air Quality Guidelines: Global Update 2005;
WHO 2021, Air Quality Guidelines: Global Update 2021.

Notes:
μg = microgram
^a 99^th percentile (3 to 4 days of exceedance per year).
^b Average of the maximum 8-hour daily O3 concentration over the six consecutive months with the highest average O3 concentration.

Note: Annual exposure and exposure during a seasonal peak are long-term exposures, while exposure over 24 hours and 8 hours are short-term exposures.

Three questions for Sébastien Denys, Director of Occupational and Environmental Health at Santé publique France

What is the impact of ambient air pollution on public health?

The impact on public health is significant both internationally and nationally. I would like to point out that the WHO estimates that approximately 7 million premature deaths each year are due to the effects of air pollution, of which more than 4 million are linked to ambient air. In France, Santé publique France recently reported that exposure to ambient air pollution from fine particulate matter (PM2.5) results, on average, in a loss of nearly 8 months of life expectancy for people aged 30 and older, and that nearly 40,000 deaths each year in France can be attributed to this exposure. These findings highlight the major public health challenge surrounding this issue and underscore the need for sustained efforts to reduce pollution from all sources.

Learn more:

• Weekly Epidemiological Bulletin "Impact of Ambient Air Pollution on Mortality in Metropolitan France: Reduction Linked to the Spring 2020 Lockdown and Long-Term Impact for the Period 2016–2019"

• Summary report "Impact of ambient air pollution on mortality in metropolitan France. Reduction linked to the spring 2020 lockdown and new data on the total burden for the period 2016–2019"

• Infographic "Ambient air pollution: a current public health issue and lessons from the spring 2020 lockdown related to COVID-19"

What is the purpose of the WHO’s proposed ambient air quality guidelines in terms of public health?

Although the WHO’s air quality guidelines are not legally binding, they are defined—and the WHO emphasizes this point—as target values for reducing the health burden associated with ambient air pollution. The goal is to achieve these new, lower—and therefore more stringent—thresholds, which will lead to stronger policies to reduce air pollutant levels and help decrease morbidity and mortality attributable to pollution exposure worldwide, thereby better protecting everyone’s health. Thus, the publication of these new thresholds should prompt authorities to revise regulatory standards. I emphasize that exceeding these new air quality thresholds is associated with significant health risks.

How does Santé publique France use the WHO’s proposed ambient air quality guidelines?

For the past 25 years, Santé publique France has coordinated an Air and Health Monitoring Program (PSAS) (see the thematic dossier) and has initiated a collaboration with the WHO within this framework. In this context, we have developed the Quantitative Health Impact Assessment (EQIS) method to assess the impact of air pollution on the health of the French population. WHO thresholds are used in these assessments as target values to be achieved. These methods allow us to estimate the expected health benefits of actions aimed at reducing pollution levels to the thresholds set by WHO guidelines. Our goal, as established in our mission, is to support local, national, and European public policies for air quality management.