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Press Conference

Disclosures: Ljungman reports no relevant financial disclosures.
September 22, 2021
3 min read

WHO issues new air quality recommendations for six major pollutants


Press Conference

Disclosures: Ljungman reports no relevant financial disclosures.
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WHO has issued new global air quality guidelines, updating its previous recommendations that were made 16 years ago.

The new guidelines aim to protect people from air pollutants, including those that contribute to climate change, according to a steering group led by WHO’s European Centre for Environment and Health.

Depiction of source quote presented in the article

“Nothing is more essential for life than air,” WHO Director General Tedros Adhanom Ghebreyesus, PhD, MSc, said during a press briefing. “The simple act of breathing contributes to 7 million deaths a year.”

Exposure to air pollution is linked to an increased risk for respiratory diseases like pneumonia, asthma, chronic obstructive pulmonary disease and severe COVID-19. It is also a major cause of noncommunicable diseases such as ischemic heart disease, stroke and cancer, Tedros said.

The updated levels on six “classical pollutants” are intended as interim targets to guide all people, including policymakers, organizations and individuals, Maria Neira, MD, MPH, director of the department of Environment, Climate Change and Health at WHO, said.

Tedros urged all countries to put the guidelines into use.

Updated levels

The pollutants include PM., PM, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. The recommendations did not include suggestions for simultaneous exposure to multiple pollutants.

WHO decreased the maximum levels of acceptable exposure to all pollutants except sulfur dioxide compared with the 2005 guidelines. Specifically, WHO recommended average exposure levels of:

  • 5 µg/m³ PM. annually compared with 10 µg/m³ in 2005;
  • 15 µg/m³ PM. over 24 hours compared with 25 µg/m³ in 2005;
  • 15 µg/m³ PM annually compared with 20 µg/m³ in 2005;
  • 45 µg/m³ PM over 24 hours compared with 50 µg/m³ in 2005;
  • 60 µg/m³ ozone during “peak season”;
  • 100 µg/m³ ozone over 8 hours;
  • 10 µg/m³ nitrogen dioxide annually compared with 40 µg/m³ in 2005;
  • 25 µg/m³ nitrogen dioxide over 24 hours;
  • 40 µg/m³ sulfur dioxide over 24 hours compared with 20 µg/m³ in 2005; and
  • 4 mg/m³ carbon monoxide over 24 hours.

The new recommended exposure level to sulfur dioxide is higher than the recommended exposure level in 2005.

“This value is believed to cut health effects to the same extent as the guidelines for other pollutants, so we believe that it is fair to have it in the form that it is now,” Michal Krzyanowski, MD, co-chair of the Guideline Development Group, told Healio Primary Care during the briefing.

Although the guidelines are “not legally binding,” they are intended as pollution level caps for all countries, according to WHO.

Intersection between air quality, health and policy

Hans Henri P. Kluge, MD, WHO regional director for Europe, said during the briefing that

“Clean air is a political choice and a societal response,” he added.

Tedros said that vulnerable populations in low- and middle-income countries are particularly affected by “poor air quality due to urbanization and rapid economic development and air pollution in the home caused by cooking, heating and lighting.”

If air quality levels are kept below WHO’s new standard for PM. alone, globally, about 80% of deaths linked to particulate matter exposure could be avoided, according to the guidelines.

Petter Ljungman, MD, an associate professor of epidemiology at the Institute of Environmental Medicine at Karolinska Institutet and senior consultant of cardiology at Danderyd Hospital in Sweden, and colleagues recently published findings in The BMJ that showed long-term air pollution exposure at levels below U.S., European Union and previous WHO guidelines was significantly associated with mortality from natural causes, CVD and respiratory disease.

Petter Ljungman

“These are significant changes for the better,” Ljungman said in response to the new WHO air quality guidelines.

He said that reductions in nitrogen dioxide levels specifically “are helpful for policy planning,” since nitrogen dioxide is a “good capture of local emissions.”

Ljungman expected that WHO’s new guidelines will put some pressure on the Environmental Protection Agency to develop and implement new U.S. air quality guidelines. However, “the U.S. is a huge country and there are vast disparities when it comes to air pollution exposure, and it is going to be challenging,” he said.

The new guidelines are particularly relevant to primary care physicians.

“It is really important to create an awareness of this issue amongst primary physicians to make sense of this and promote this for the general audience as well as for their patients to actually come to terms with changes that need to be done to secure health,” Ljungman said. “As doctors, we work with patients and we do a lot of secondary prevention, but at the end of the day, we are interested in having good health to start off with. We are interested in prevention, and pollution is a scenario where we can do a lot to provide prevention and protection from becoming sick.”


WHO global air quality guidelines: particulate matter (‎PM2.5 and PM10)‎, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. Published Sept. 22, 2021. Accessed Sept. 22, 2021.

Strak M, et al. The BMJ. 2021;doi:10.1136/bmj.n1904.