Move over, stress and high blood pressure—there’s a new risk factor threatening your heart’s health, and it’s lurking in communities across Canada. For years, physicians and scientists have advised Canadians to stop smoking, become physically active and eat a healthy diet, all to combat risky lifestyle habits that contribute to heart disease. Now, a new menace has joined the ranks, and you breathe it every day.

Research has discovered that outdoor air pollution can raise your risk of heart disease and stroke. In 2008, according to the Heart and Stroke Foundation, short- and long-term exposure to air pollution were estimated to result in 21,000 premature deaths in Canada, as well as 620,000 doctor visits, 92,000 emergency- department visits, 11,000 hospital admissions and an annual economic impact of more than $8 billion.

This upswing in pollution-related heart problems isn’t just a Canadian phenomenon. In 2013, the medical journal The Lancet examined 35 studies from 12 countries, including the United States, China and the United Kingdom. The report confirmed what many scientists have suspected over 15 years of investigation: There’s a definite association between air pollution and heart disease, and increasing numbers of people around the globe are having heart attacks and strokes because of it.

What is polluting the air?
Much of the blame lies with fine particulate matter, a hazardous chemical cocktail of liquid and solid material that’s released into the air by vehicle exhaust, forest fires, wood-burning stoves and industrial emissions. “These gases and particles are invisible to the human eye and contain a mix of hundreds, maybe thousands, of chemicals,” says Michael Brauer, professor at the school of population and public health at the University of British Columbia.

When you take a breath, these tiny particles travel deep inside your lungs. Defence mechanisms in the lungs that usually tackle and eliminate incoming viruses and bacteria view the inhaled particulates as alien invaders and react by dispatching cells to the site to repair the damage. The resulting inflammation—similar to the response our bodies might have to a cut on the skin—doesn’t help. “Our inflammatory response isn’t effective in destroying the particulate matter, so the inflammation continues,” says Brauer. “Eventually, the inflammatory cells spill over into the bloodstream and go to work on the blood vessels in your heart.”

How air pollution affects your heart
This inflammation can cause cardiovascular damage through an increased risk of blood clots, increased blood pressure and atherosclerosis—a buildup of sticky plaque, consisting of fat, cholesterol and calcium, that hardens and narrows the walls of the arteries. Atherosclerosis can severely restrict or block flow through the arteries, creating the perfect conditions for a heart attack or stroke— even death.

Air pollution can also affect heart rate variability through the activation of irritant receptors in the lungs and the autonomic nervous system response. “Plaque is unstable,” says Dr. François Reeves, interventional cardiologist and associate professor of medicine at the University of Montreal and author of Planet Heart: How an Unhealthy Environment Leads to Heart Disease. “A single stressful moment like being angry can raise your blood pressure, increase your heart rate and cause the plaque to rupture. Pow! You have a heart attack.” On a fragile artery, a plaque rupture could be triggered by a variety of environmental stressors (like smog), physiological stressors (such as unstable diabetes or strenuous activity) or psychological stress.

Traditionally, diabetes, an unhealthy diet, physical inactivity, excess weight, high cholesterol, stress, high blood pressure, a family history and smoking are recognized as the main risk factors of cardiovascular disease. While air pollution hasn’t been shown to be any more dangerous than these common factors, Canadians shouldn’t ignore what is becoming a major health concern. The problem with air pollution is that everyone is exposed to it. “You can avoid smoking, alcohol and dietary risk factors, but it’s difficult to avoid air pollution,” says Brauer. “You can lower your exposure, but you can’t avoid it altogether.”

Dr. Stephan van Eeden, internist and respirologist at St. Paul’s Hospital in Vancouver, professor of medicine at the University of British Columbia and spokesperson for the Heart and Stroke Foundation, says that those who are most vulnerable to the damaging effects of air pollution already have the traditional risk factors. “Most hospital admissions associated with air pollution usually involve people who are at risk, such as those with diabetes or high blood pressure, or individuals with a known underlying heart disease. They’re more sensitive,” he says.

Air pollution in Canada
Overall, when compared to the United States, Europe and China, Canada’s air is quite clean, though some areas of our country have more pollution than others. In 2008, the Heart and Stroke Foundation used Environment Canada data to create a report card grading air quality and cardiovascular risk for Canadians.

The highest readings of heart-threatening particulate matter were found in Ontario, Quebec and the Interior of British Columbia. Heavy industry, excessive traffic along the Quebec City–Windsor corridor and wood burning in northern regions earned Ontario and Quebec an F grade, while B.C.’s Interior also received an F, thanks to pollution trapped between its mountain ranges. New Brunswick (C), Manitoba (B+) and Newfoundland and Labrador (B+) received the best grades across the country.

Canadian cities are generally more polluted than rural areas, except in the winter, when wood-burning stoves are used for heat. In warmer seasons, forest fires, climate change (due to excess heat being trapped in our atmosphere), geographical conditions and seasonal changes are also problematic. Adding insult to injury, pollutants from other countries regularly blow into Canada. “In B.C., we get air pollutants from China,” says Dr. van Eeden. “You can’t say because you don’t live in China that you don’t have to worry about air pollution there. It’s a global problem. We need to be very proactive.”

How to lower your risk of cardiovascular disease
Here’s the good news: Breathing polluted air doesn’t have to mean a death sentence; there’s a lot you can do to protect your heart’s health. “The healthier you are, the less likely you’ll be affected by air pollution,” says Brauer. Maintain a healthy diet and weight, avoid smoking, limit your alcohol intake, don’t live near major highways and participate in regular physical activity. When exercising outdoors, run in a park or along a leafy side street instead of a busy road and select a time when air pollution is low.

“Choose early morning, before rush hour, or evening, instead of late afternoon, when we get higher levels of air pollution,” says Brauer. Schedule outdoor activities when air quality is best by checking Environment Canada’s online air quality health index for daily air-pollution levels in your community.

And do your part to clean up our air. Take public transit, use your car only when absolutely necessary, choose a wood-burning stove approved by the Canadian Standards Association and opt for electricity-powered lawn mowers and leaf blowers over gasoline-fuelled lawn equipment. You can also put pressure on your local and federal governments to continue their work on reducing air pollution.

Find out what six lifestyle changes will help prevent heart disease.

This content is vetted by medical experts

This story was originally titled "Something in The Air" in the February 2015 issue.             Subscribe to Canadian Living today and never miss an issue!