Photo: file photo
The Bennett Bridge choked with smoke from a wildfire in August 2019
Exposure to dirty air in Canada leads to nearly 8,000 deaths a year, a new study suggests.
The study, published today in a Health Effects Institute (HEI) report, looked at mortality in 7.1 million Canadians over the past 25 years.
Long-term exposure to particulate matter (PM2.5) has been found to be most harmful when combined with other pollutants such as ozone. As of 2016, this resulted in 7,848 deaths per year, although this is likely an underestimate compared to what Canada is experiencing now.
But even low concentrations of PM2.5 – a pollutant spewed into the air by forest fires, wood-burning stoves and fossil fuel emissions from cars and trucks – have been found to contribute to an increased risk of death in people who already suffer from heart disease. -vascular and heart diseases, diabetes, pneumonia or respiratory disease such as COPD.
“There really is no safe level of air pollution,” said lead study author Michael Brauer, a professor in the School of Population and Public Health at the University of British Columbia.
Brauer and his colleagues combined satellite data, local air samples and atmospheric modeling to measure PM2.5 concentrations in Canada from 1981 to 2016.
After analyzing the data, the researchers found that cities had particulate matter concentrations between nearly three and eight times higher than rural areas. By 1990, the highest concentrations of PM2.5 were found in major cities, including Vancouver, Toronto, Hamilton and Quebec City.
And while these pollutant levels decline in subsequent years, even low levels increase the risk of premature death.
“We chose the low-hanging fruit”
Brower’s data softens the results of a study released last year in which Health Canada estimated that all forms of air pollution contribute to the early deaths of 15,300 Canadians each year.
In this study, interior British Columbia suffers from some of the worst air pollution impacts in the country.
Between 2013 and 2018, the 10 census tracts in the country with the highest PM2.5 exposure were in interior British Columbia, according to Health Canada’s 2021 analysis of the impact of air pollution on human health .
Of those, half the census tracts — including the Central Kootenay, where Nelson is located — were among the top 10 parts of the country with the highest per capita premature death rates.
Brower said climate change, from rising urban temperatures to devastating wildfires, threatens much of the progress made in recent decades.
“We picked the low-hanging fruit,” he said. “With a warmer climate, things are unlikely to improve without more aggressive action… And the faster we decarbonize. the faster we will eliminate these health impacts.”
The growing impact of bad wildfire seasons has some medical professionals rethinking how they diagnose health crises. After a record-breaking heat wave and brutal fire season, one British Columbia doctor even diagnosed a patient as suffering from “climate change.”
“A lot of people in the Kootenays thought it would be a good place to hide while the rest of the world fell apart. But of course it’s hitting us here, just like it’s hitting a lot of places, and we’re really seeing the impact,” said Dr. Kyle Merritt, head of Kootenay Lake Hospital in Nelson.
The global death toll from air pollution is likely much higher
Every year worldwide, the World Health Organization (WHO) estimates that outdoor air pollution causes about 4.2 million deaths. Brauer’s research would increase that estimate by another 1.5 million.
Yet few jurisdictions have air quality standards that reflect the risk Brower found in his study. Canada’s 2012 Ambient Air Quality Standards set a path to reduce air pollutants through a phased approach until 2025. Current standards recommend PM2.5 concentrations below 8.8 micrograms per square meter.
In the US, the national standards are 12 micrograms per square meter.
Meanwhile, recently updated WHO standards lower that threshold to 5 micrograms per square meter.
But none of those pollution limits meet the 2.5 micrograms per square meter limit above which Brauer says increases the risk of mortality.
This should be a signal to regulators both in Canada and around the world that air quality standards need to be strengthened, Brower said.
“Globally, that means we have to keep going,” he said. “It’s going to be there – even relatively clean countries, Western Europe, North America … it still has a significant impact.”
Photo: Contributed
PM2.5 concentrations fell throughout the study period, but even low levels of exposure significantly affected the risk of premature death. Brauer et al. (2022)
The UBC-led study is the latest in a series of HEI-backed studies looking at how even low levels of outdoor air pollution affect human health.
The first, a 2021 study looking at the effects of particulate matter, black carbon, nitrogen dioxide and ozone in 11 European countries, found “significant” links between those exposed to low levels of pollution and early mortality in people with cardiovascular disease. and respiratory diseases and lung cancer.
The second report, released earlier this year and focused on the United States, tracked low levels of air pollution exposure among 68.5 million older Americans. Once again, history repeated itself: even low levels of exposure to particulate matter increased the risk of death.
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