A phase-out of coal power plants in Ontario is proving a boon to Toronto's air quality, while reliance on the fossil fuel in Alberta has been linked to deaths.

Canada's largest city, also known as the Big Smoke, is now subject to less fine particulate matter than the much smaller capital of Alberta, Edmonton, according to a study by the Canadian Association of Physicians for the Environment released Tuesday. Pollutants including nitrates and sulfate coming downwind from coal plants in the western province have led emissions in Edmonton to exceed Toronto's by 25 per cent, the study found.

Particulate matter from coal plants has been identified as a cancer-causing substance, and about 100 deaths a year in Alberta are associated with the emissions. The last of Ontario's coal plants was shuttered last year, while Alberta increased generating capacity from coal in 2014.

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"We don't get to choose the air we breathe," Joe Vipond, who heads the Canadian doctors association's effort to phase out coal plants in Alberta, said in an interview.

While coal plants are the biggest cause of Edmonton's deteriorating air quality, a growing population and more vehicle use are also factors, the report said.

Alberta and Saskatchewan lead the country in the use of coal for electricity, and both provinces have the highest per capita carbon emissions in Canada, at more than 60 tonnes, compared with 12.5 tonnes in Ontario, according to Environment Canada figures. Alberta Premier Jim Prentice has said he'll consider a review of coal plants as part of a revamped climate policy expected in the coming months.

Ontario's coal phase-out and policies to boost the use of renewable energy has resulted in a 19-per-cent reduction in carbon emissions since 2005, according to a report by the Pembina Institute, a Calgary-based environment group.

Canada's most populated province also announced on Monday that it would join a California-Quebec cap-and-trade system to further lower emissions of the greenhouse gas.