A recent study involving McGill researchers
now suggests that the annual global death toll from outdoor PM2.5 may be
significantly higher than previously thought. That’s because the researchers
found that mortality risk was increased even at very low levels of outdoor
PM2.5, ones which had not previously been recognized as being potentially
deadly. These microscopic toxins cause a range of cardiovascular and
respiratory diseases and cancers.
The World Health Organization’s most recent
estimates (2016) are that over 4.2 million people die prematurely each year due
to long-term exposure to fine particulate outdoor air pollution (often referred
to as PM2.5,).
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 metre. The current United States
Environmental Protection Agency standard of 12 (ug) per cubic metre is now more
than double the value recommended by the WHO.
“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, 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 advances global understanding of
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 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 result? An improved understanding of how air pollution
impacts health on a global scale.
“One take away 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:
Scott Weichenthal et al, How low can you go? Air pollution affects
mortality at very low levels,Science Advances, DOI10.1126/sciadv.abo3381