Both indoor and outdoor air pollution can lead to potentially fatal heart effects, according to a new study, which gleaned data from study subjects wearing air pollution monitoring vests.

In a study of 65 people, researchers from the University of Michigan found that a 10 microgram per cubic metre increase in exposure to pollution, such secondhand smoke, car exhaust or indoor heating systems:

• narrowed arm blood vessel diameter by 18 per cent after two days of exposure
• led to nearly a two-point jump in blood pressure on the day after exposure

Constricted blood vessels and high blood pressure are risk factors for heart attack and stroke.

"At the community level, a 10 microgram per cubic metre increase in pollution leads to a one per cent increased chance of dying the next day," lead study author Dr. Robert Brook, an associate professor of medicine at the University of Michigan Ann Arbor, said in a statement. "Within a city of one to five million, that increase would lead to about one death per day."

Brooks presented his findings this week at the American Heart Association's Scientific Sessions 2008 conference in New Orleans.

Air pollution has been linked to more than 9,000 premature deaths each year in Canada and more than 800,000 deaths worldwide.

Therefore, Brooks and his team set out to determine if day-to-day exposure to air pollutants could immediately increase heart attack and stroke risk.

For his study, Brooks included both men and women who ranged in age from 19 to 80. They were from diverse ethnic backgrounds, were non-smokers and lived in three different Detroit neighbourhoods.

Over three years, subjects wore the vests for five days in winter and five days in summer, and study investigators measured blood pressure and blood vessel function at the end of each day.

The vests themselves measured personal exposure to pollution, while the researchers also measured the amount of ambient pollution the subjects were exposed to according to data from regional community monitoring stations.

They found that it was the combined exposure to personal and community pollutants that led to the effects on both blood pressure and blood-vessel function, Brooks said.

People, particularly those who have other risk factors for heart attack and stroke, should minimize their exposure to air pollutants by installing indoor air filters and avoiding walking in high-traffic areas, experts suggest.

"When you exercise outdoors try to stay away from major roadways and don't exercise if there is a smog alert," Prof. Bruce Urch, an air pollution expert at the University of Toronto, told CTV News.

The key is to also avoid exposure to secondhand smoke, a major source of air pollution.

The study found that even though subjects were non-smokers who lived in non-smoking homes, about 30 per cent of them were still exposed to secondhand smoke.

With a report from CTV's medical specialist Avis Favaro and senior producer Elizabeth St. Philip