WHO Slashes Safe Air Pollution Levels As New Evidence Highlights Health Risks


Ben Taub

Freelance Writer

clockSep 23 2021, 17:12 UTC
Air pollution

Air pollution is more of a health risk than previously thought, according to the WHO. Image: Mikhail Starodubov/

For the first time since 2005, the World Health Organization (WHO) has updated its global air quality guidelines, recommending that concentrations of fine particulate matter be at least halved. Explaining this drastic reduction in safe contamination levels, the WHO insists that “there is now a much stronger body of evidence to show how air pollution affects different aspects of health at even lower concentrations than previously understood.”

“The guidelines recommend new air quality levels to protect the health of populations, by reducing levels of key air pollutants, some of which also contribute to climate change,” said the organization in a statement accompanying its new report.


In recent years, health officials have become increasingly alarmed by the threat posed by tiny particles called PM2.5, which have a diameter of 2.5 microns or less. Typically produced as a result of burning fuel, these microscopic particles are small enough to pass from the lungs into the bloodstream, potentially damaging other organs and jeopardizing cardiovascular and respiratory function.

When the WHO last updated its air pollution guidelines 16 years ago, it recommended that annual PM2.5 levels be kept to below ten micrograms per cubic meter of air. In light of new evidence, however, it now urges all member nations to limit PM2.5 to just five micrograms per cubic meter of air over the course of a year.

This adjustment comes after a “systematic review of accumulated evidence”, which indicated that exposure to air pollution is now “one of the biggest environmental threats to human health” and causes around 7 million premature deaths worldwide every year.


“In children, this could include reduced lung growth and function, respiratory infections and aggravated asthma,” explains the WHO. “In adults, ischaemic heart disease and stroke are the most common causes of premature death attributable to outdoor air pollution, and evidence is also emerging of other effects such as diabetes and neurodegenerative conditions.”

In addition to curbing PM2.5, nations are also urged to limit five other major pollutants, including ozone, nitrogen dioxide, sulphur dioxide, and carbon monoxide. Particles measuring less than ten microns in diameter – known as PM10 – are also on the list of offending items that must be reduced.

 Not to be confused with the ozone layer, ozone at ground level is a major constituent of smog and forms when sunlight interacts with other pollutants in the air. Capable of triggering an array of respiratory problems, ozone levels tend to fluctuate with the seasons, although in 2005 the WHO recommended that maximum concentrations be kept below 100 micrograms per cubic meter of air over an eight-hour period. In its latest update, this figure has been revised to just 60 micrograms per cubic meter of air.


“Air pollution is a threat to health in all countries, but it hits people in low- and middle-income countries the hardest,” said WHO Director-General, Dr Tedros Adhanom Ghebreyesus. “WHO’s new Air Quality Guidelines are an evidence-based and practical tool for improving the quality of the air on which all life depends. I urge all countries and all those fighting to protect our environment to put them to use to reduce suffering and save lives.”

To achieve these targets, the organization recommends that governments take a multi-faceted approach that includes investing in green energy solutions and public transport, improving waste management, and providing access to cleaner fuels for heating and cooking at home.


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