Researchers at the University of British Columbia have discovered that even low levels of air pollution — below national air quality guidelines — are associated with an increased risk of death in Canada.

According to a study published this week in a Health Effects Institute report, there is no safe level of air pollution when it comes to Canadians' health outcomes.

"Somewhere around 10,000 people are dying prematurely from air pollution every year in Canada," said Michael Brauer, the study's lead author and a professor at the university's School of Population and Public Health. "It's bigger than the impacts of motor vehicle collisions. It's bigger than the impact from alcohol abuse."

Brauer says researchers found at least a five per cent increase in the risk of death when comparing high- and low-pollution areas in Canada.

Even though Canada is one of the few countries that meets World Health Organization air quality guidelines, he says the results are concerning because most Canadians live in more polluted areas, such as large urban centres.

Brauer refers to air pollution as a "silent killer" — even though its effects aren't obvious, when combined with other factors and health risks, they have a big impact.

"Air pollution affects many of the main causes of death already," he said. "If somebody dies of a heart attack we actually never know exactly what the cause of that heart attack is, or even of the heart disease that developed that led them to be susceptible to that heart attack."

Life expectancy lowered by half a year

The study analyzed weather data and pollution-monitoring stations across the country to get an estimate of air pollution for every square kilometre in Canada going back to 1981.

With census results from Statistics Canada, the researchers were able to determine the level of air pollution Canadians were exposed to over time. They then looked at death records and ruled out other factors that affect the risk of dying to establish the correlation between pollution and increased death risk.

The researchers say air pollution is the fourth highest risk factor for death globally and by far the leading environmental risk factor for disease. (File Photo)

Brauer says, on average, Canadians' life expectancy is about half a year lower because of air pollution.

"It's kind of like if you removed air pollution, it's like snapping your finger and giving everybody with a magic wand an extra half year of your life," he said. "But obviously for some people it may be more and some people may be less."

He explains that many larger sources of pollution in Canada have been reduced over the last 40 or 50 years, but cities can still improve air quality by becoming "low-emission zones." Cities could achieve this in several ways, including charging vehicles a tax for driving into city centres, using congestion charges, or even prohibiting more polluting vehicles from entering cities in the first place.