Air pollution behind additional 1.5 million premature deaths annually

Toronto: Fine pollution particles (PM2.5) may be responsible for 1.5 million additional premature deaths around the globe each year, according to a study which found that low levels of air pollution are dangerous than previously thought.

The World Health Organization's most recent estimates are that over 4.2 million people die prematurely each year due to long-term exposure to fine particulate outdoor air pollution referred to as PM2.5.

The latest study, published in the journal Science Advances, suggests that the annual global death toll from outdoor PM2.5 may be significantly higher than previously thought.

That is because the researchers found that mortality risk was increased even at very low levels of outdoor PM2.5, which had not previously been recognised as being potentially deadly.

These microscopic toxins cause a range of cardiovascular and respiratory diseases and cancers.

"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 Scott Weichenthal, Associate Professor at McGill University in Canada and the lead author on the paper.

The researchers combined 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 PM2.5, 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 PM2.5 levels.

The study found 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 5 microgrammes (ug) per cubic metre.

"One take away is that the global health benefits of meeting the new WHO guideline are likely much larger than previously assumed," said 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," he added.

A better understanding may allow us to be much more efficient in designing regulatory interventions to improve population health, the researchers added.