Low levels or particulate matter pollution deadlier than previously thought

November 15, 2022

Canadian researchers have found the annual death toll resulting from fine particulate outdoor air pollution, called PM2.5, may be responsible for more premature deaths than previously thought.

Particulate matter contains microscopic solids or liquid droplets 30 times smaller than a human hair. They are so small they can be inhaled and cause serious health problems, like premature death in people with heart or lung disease, heart attacks, asthma and other respiratory and cardiovascular problems.

Long-term exposure to particulate matter was also found to increase the severity of COVID-19 health outcomes, including death, in unvaccinated persons.

The World Health Organization estimated in 2016 that more than 4.2 million people die prematurely each year due to long-term exposure to PM2.5, but McGill researchers found the actual number may be 5.7 million.

McGill researchers combined health and mortality data for seven million Canadians gathered over a 25-year period and information about particulate matter concentrations across the country during that time period.

“We found that outdoor PM2.5 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 environmental epidemiologist and study lead author Scott Weichenthal.

The WHO recently introduced a 5-microgram-per-cubic-meter guideline for annual outdoor fine particulate air pollution, which it said would help decrease the health burden resulting from exposure to air pollution worldwide. The guideline is not legally binding, but sets the maximum level of PM2.5 exposure in a year that the WHO believes is safe for human health.

The U.S. Environmental Protection Agency’s currently has a PM2.5 standard of 12 micrograms per cubic meter, more than double the WHO’s recommendation. The standard is based on the amount of pollutants considered harmful to people and the environment and sets the federal limit for the amount of pollutants allowed by law.

The Trump administration in its final days decided it would not update the National Ambient Air Quality Standard for particulate matter, essentially keeping it in place for five years unless the Biden administration moved to update it.

The Biden administration announced it would reconsider the NAAQS decision and issue a new standard for review by summer 2022. The EPA Clean Air Scientific Advisory Committee issued a report in March, but the EPA still has not issued a new PM2.5 standard.

Low levels or particulate matter pollution deadlier than previously thought