Polluted air damages hearts as well as lungs

By Terri Coles

TORONTO (Reuters) -- While the effects of air pollution on people with respiratory issues are well-known, many people are still unaware of the risks to heart health. A national poll by the Heart and Stroke Foundation in Canada found that only 13 percent of Canadians have made the connection between air pollution and cardiovascular disease.

"There's no doubt that for quite some time, air pollution has been under the radar when it comes to heart disease," said Dr. Beth Abramson, a cardiologist and spokesperson for the Heart and Stroke Foundation.

Air pollution comes from a variety of sources: factories, cars, diesel trucks, power plants, dust, smoke from fireplace and wood stoves. When we think of air pollution, the smog that occurs on humid days in the summer may be the first thing that comes to mind, but a third of the dangerous fine particulate matter pollution in the air comes from wood-burning stoves and fireplaces, Abramson said. That means that air pollution is not just a city problem but something that affects rural areas as well, and that it's a year-round concern.

Just a small increase in particulate matter can be dangerous -- every 10-microgram per cubic meter increase in long-term exposure to particulates can increase the risk of dying of heart disease or a stroke, by as much as 76 percent in some people. In the short-term, a day-to-day increase in particulates as low as 20 micrograms per cubic meter can raise the risk of a heart attack within 24 hours by 69 percent, the Heart and Stroke Foundation said.

The American Heart Association predicts that 60,000 Americans die each year due to the small particulate matter in air pollution. About 6,000 Canadians die annually because of short-term exposure to air pollution, the Heart and Stroke Foundation said, and research indicates that almost 70 percent of those deaths are heart-related. Studies done over the past ten years show a consistent increased risk of cardiovascular events like heart attacks and strokes related to short-term and long-term pollution, the AHA said, especially particulate matter.

The evidence connecting bad air days and an increased risk of heart-related issues, like hospitalization for a heart attack or stroke, is strong, said Abramson.

There are Canadian data showing that more people have heart attacks and more die of heart disease on days where the air quality is poor, and that data would apply to most Western industrialized countries, said Dr. Peter Liu, the scientific director for the Institute of Circulatory and Respiratory Health at the Canadian Institutes of Health Research. A study by the Health Effects Institute, a Massachusetts-based non-profit, found that death rates in the 90 largest cities in the U.S. rose by 0.5 percent with an increase in small particulate matter of only 10-micrograms per cubic meter.

The paradox of this is that most people with lung problems know how to protect themselves on smog days, but those with heart disease aren't aware of the risk, Liu said. "The surprising part is that if you actually look at the statistics, on a bad pollution day you have at least four to five times the chance of getting a heart attack or of having heart failure."

The lack of awareness about the connection between air pollution and heart disease stems from the nature of the disease, Liu said. When you have lung disease, the symptoms for complications are noticeable -- like difficulty breathing. But with heart problems, you don't necessarily notice a change until something catastrophic happens, he said.

"People with lung disease get the warning, so they know they should avoid (bad air)," Liu said. "But heart disease patients might not get that warning. They only know when they develop the complications and by that time, it's too late."

There is growing evidence that air pollution affects long-term heart health as well. "We now have good evidence to suggest that pollution can affect blood vessels, and potentially even the rhythm of the heart," Abramson said. Heart disease and stroke are still the greatest health threat to Canadians, she said, and there is a cumulative cardiovascular risk from long-term exposure to particulates.

Animal studies have shown that there is damage to blood vessels from long-term exposure to air pollution, Liu said -- it accelerates the development of artery plaque and hardening and increases the risk of heart attacks. One study at New York University's medical school found that mice that breathed air as polluted as that in New York City were more likely to develop atherosclerosis, or hardening of the arteries, especially when they also ate a high-fat diet.

Data also suggests that people living along busy highway corridors have higher rates of heart attack and heart disease, Liu said, though that association is difficult to track because the data is episodic. The American Heart Association found that even within the same city, people living along a busy road were more likely to die of heart-related causes.

Heart patients -- and diabetics, who have an associated risk of heart problems -- can avoid complications from small particulate matter on days with poor air quality by taking the same preventative measures that those with lung problems do, Liu said: staying inside, keeping cool and avoiding sudden, severe exertion. It's also important to make sure that your medications are up to date so your health problems are under control, he added.

In the short and long term, people can help themselves and others by trying to reduce air pollution -- walking or taking transit instead of driving on a smog day, for example. The Heart and Stroke Foundation is also running a letter-writing campaign for those who want to contact local politicians about environmental policy related to air pollution. "We need to make small individual steps to reduce pollution for ourselves and others," Abramson said.