Previously Considered Safe – Low Levels of Air Pollution Much Deadlier Than Scientists Thought

According to the study, fine particulate matter is responsible for an additional 1.5 million premature deaths each year.

According to the World Health Organization, over 4.2 million people die prematurely each year due to long-term exposure to fine particulate outdoor air pollution, also known as PM_2.5. However, a recent study involving researchers from McGill University suggests that this number may be underestimated. The study found that mortality risk was increased even at very low levels of PM_2.5, levels that were previously not considered dangerous. These microscopic toxins can cause a variety of cardiovascular and respiratory diseases, as well as cancers.

“We found that outdoor PM_2.5 may be responsible for as many as 1.5 million additional deaths around the globe each year because of effects at very low concentrations that were not previously appreciated,” said Scott Weichenthal, an Associate Professor in the Department of Epidemiology, Biostatistics, and Occupational Health at McGill University and the lead author on the recent paper in Science Advances.

Canadian Data Leads to Advances in Global Understanding of the Effects of Outdoor Pollution

The researchers arrived at this conclusion by combining health and mortality data for seven million Canadians gathered over a twenty-five-year period with information about the levels of outdoor PM2.5 concentrations across the country. Canada is a country with low levels of outdoor PM_2.5, making it the perfect place to study health impacts at low concentrations. Knowledge gained in Canada was then used to update the lower end of the scale that is used to describe how mortality risk changes with outdoor PM_2.5 levels. The result? An improved understanding of how air pollution impacts health on a global scale.

The WHO recently set out ambitious new guidelines for annual average outdoor fine particulate air pollution, cutting its earlier recommendations in half, from concentrations of 10 to concentrations of 5 micrograms (ug) per cubic meter. The current United States Environmental Protection Agency standard of 12 (ug) per cubic meter is now more than double the value recommended by the WHO.

“One takeaway is that the global health benefits of meeting the new WHO guideline are likely much larger than previously assumed,” adds Weichenthal. “The next steps are to stop focussing only on particle mass and start looking more closely at particle composition because some particles are likely more harmful than others. If we can gain a better understanding of this, it may allow us to be much more efficient in designing regulatory interventions to improve population health.”

Reference: “How low can you go? Air pollution affects mortality at very low levels” by Scott Weichenthal, Lauren Pinault, Tanya Christidis, Richard T. Burnett, Jeffrey R. Brook, Yen Chu, Dan L. Crouse, Anders C. Erickson, Perry Hystad, Chi Li, Randall V. Martin, Jun Meng, Amanda J. Pappin, Michael Tjepkema, Aaron van Donkelaar, Crystal L. Weagle and Michael Brauer, 28 September 2022, Science Advances.
DOI: 10.1126/sciadv.abo3381

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