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Air pollution is a rising and pervasive threat to cardiovascular health, but most Canadians don't realize the danger, the Heart and Stroke Foundation of Canada says.

In its annual report on Canadians' health released yesterday, the foundation said short- and long-term exposure to year-round air pollution is contributing to thousands of deaths across the country each year.

There are about 6,000 additional deaths in Canada annually because of short-term exposure to air pollution alone, the report said, and 69 per cent of those deaths result from cardiovascular events such as heart attack or stroke.

"It's an important and emerging risk factor," Beth Abramson a Toronto cardiologist and spokeswoman for the Heart and Stroke Foundation, said at a news conference to release the report, which also graded provinces on air quality.

"We still need to pay attention to the traditional risk factors for heart disease - high blood pressure, smoking, diabetes, being overweight, being out of shape [and] high cholesterol - but this is an additional risk factor that we can actually influence and influence the risk for others as a community," she said.

Length of exposure to airborne pollutants is a critical factor in cardiovascular disease risk: Research suggests that every 10-unit increase in long-term exposure to fine particulate matter (PM2.5) can increase the risk of dying from heart disease and stroke by up to 76 per cent.

Short-term exposure also can be dangerous: One study showed that a day-to-day increase from even relatively low levels of particulate matter can boost risk of a heart attack within 24 hours by 69 per cent.

Yet Environment Canada estimates that almost a third of Canadians are being exposed to higher than the 30 units (expressed as milligrams per cubic metre) of fine particulate matter deemed an acceptable level, and which Canada is hoping to achieve by 2010.

"Local air pollution can be derived from many different sources, including factories, cars, diesel trucks, power plants, wind-blown dust and smoke from wood stoves and backyard burning," Dr. Abramson noted.

And poor air quality isn't a phenomenon restricted to large cities with pollution-spewing vehicles and industrial sites, she said. Residents in rural areas that may seem environmentally more pristine are also bearing the brunt of bad air.

"Air pollution can also be exported across long distances, as much as 800 kilometres for PM2.5."

The Heart and Stroke Foundation is calling on the federal and provincial governments to implement a number of measures, including legislating stricter pollution standards and expanding the daily air quality health index to communities across the country so at-risk Canadians can limit outdoor activities on high pollution days.

Dr. Abramson said some people are more vulnerable to airborne pollutants than others, in particular the elderly and those already at risk for cardiovascular disease, such as diabetics, and she advised that people moderate their outdoor activities when pollution is high.

"Unfortunately, people who are trying to lead a heart-healthy life by being physically active actually are exposing themselves to more risk on bad air days ... if they go outside to exercise."

In a report card on the provinces, the foundation gave British Columbia's interior, Ontario and Quebec a grade of F, based on the highest levels of fine particulate matter in a 24-hour period observed over a year. All significantly exceeded 30 units.

The B.C. interior has high levels of particulate matter because pollution gets trapped between mountain ranges. (B.C.'s lower mainland received a D because of pollution hot spots.) Ontario and Quebec are affected by the Quebec City-Windsor, Ont. traffic corridor, as well as heavy industry and wood-burning in their northern regions.

Alberta earned a D because pollution blows out of the province into neighbouring provinces and the United States from resource-based industrial areas such as the tar sands.

New Brunswick, which has high levels of wood-burning, was awarded a C, while Manitoba and Newfoundland scored a B-plus because winds tend to clear out air pollution except in some hot spots. Figures were not available for Saskatchewan, Nova Scotia or Prince Edward Island.

Stephen Samis, director of health policy for the foundation, said a survey the organization commissioned of more than 1,100 Canadian adults showed that six in 10 believe air quality in their community is generally good to excellent, but just 3 per cent knew air pollution is a year-round problem.

"It's important to realize that air pollution is not just a summer and urban problem, it's a winter and rural problem as well," Mr. Samis said. "In fact, during winter months, wood-burning stoves and fireplaces can be sources of dangerous air pollution, particularly in rural areas."

The survey found wood-burning stoves and fireplaces are responsible for 28 per cent of fine particulate matter pollution in Canada and that 44 per cent of those living in communities of less than 10,000 residents have a wood stove, pellet stove or fireplace; of those, 70 per cent use it daily or almost daily during winter.

Air quality nationwide

Research has shown that poor air quality plays a major role in cardiovascular disease. Here annual provincial air pollution levels were measured and graded for their impact on heart health.

Note: Unmarked provinces had no data available

*amount of particulate matter in the air

(highest 3-year average 98th percentile PM2.5 in ug/m3)

SOURCE: HEART AND STROKE FOUNDATION, ENVIRONMENT CANADA