Polluted air does more than hurt your lungs, it can affect your heart, according to research.
Heart conditions are responsible for a huge portion of the millions of deaths caused by air pollution worldwide every year, according to a recent study.
A paper published in the European Heart Journal estimated that air pollution was responsible for an additional 8.8 million deaths in 2015, and between 40 and 80 per cent of those are from cardiovascular diseases like heart attack and stroke.
In Canada, about 14,400 deaths per year are attributable to air pollution, Health Canada estimated in a 2017 paper. Another Canadian study that same year had a lower estimate: 7,700.
“It has long been recognized that while there is a mountain of morbidity due to lung disease from air pollution, the majority of deaths from air pollution are from cardiovascular disease,” said Dr. Christopher Carlsten, a professor of medicine and director of the air pollution exposure lab at the University of British Columbia.
The bad air, which contains harmful gases and particles, moves from your lungs into your cardiovascular system in three main ways, he said.
When pollution enters your lungs, it can cause inflammation. That inflammation can then spread through the thin tissue of the lungs into the bloodstream, where it circulates and can cause cardiac and vascular problems like heart attacks or stroke, he said.
There’s also increasing evidence that the tiny particles in pollution themselves can enter the bloodstream directly and cause damage, he said.
“The usual common pathway to a heart attack is something irritates the lining of the arteries and then causes deposition of fatty plaques, also known as atherosclerosis,” said Dr. Sonia Anand, a professor of medicine at McMaster University who holds a Heart & Stroke Foundation chair in population health. Pollution can be that irritant.
Air pollution also interacts with the nervous system, Carlsten said. As the nervous system controls the heart, this might lead to heart rhythm disturbances, according to a position statement from Heart & Stroke.
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It’s tricky to say exactly how much air pollution increases your risk of cardiovascular conditions, said Michael Brauer, a professor at UBC’s School of Population and Public Health who studies the global impacts of air pollution.
“There’s no air pollution disease,” he said. “There’s no tests you can do. It never shows up on anybody’s death certificate.”
“These health problems that are affected by air pollution are health problems that also have other things contributing to them.”
Your risk of coronary heart disease — a condition where narrowed arteries can lead to heart attack — is affected by your diet, your physical activity, whether you smoke — and likely also by air pollution, he said. “At the end of the day, we can never say whether it was your diet or air pollution that was the straw that broke the camel’s back.”
“That’s not even the right way to think about it. All of them are contributing. If you remove one, the other ones are still there.”
Infants, the elderly, and people with existing heart conditions are most likely to be negatively affected by air pollution, Carlsten said.
Unfortunately, he said, studies have shown that the risk of cardiovascular conditions increases significantly at even fairly low levels of pollution exposure. “It doesn’t take nearly as much pollution as we had previously thought to cause adverse effects.”
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So what can you do about it?
Anand said the research is still too new for doctors to regularly ask you about your pollution exposure the same way they ask if you’re a smoker. “Quite honestly, it’s relatively new as a risk factor for cardiovascular disease to the point where we don’t include it in our individual patient risk assessment,” she said.
“I don’t think we have enough information about how it would change your management.”
“Would it be enough to recommend that an individual move from their environment or something as radical as that?”
Better studies on things like whether wearing masks outside or installing an air filter in your home cut your risk would help doctors figure out what to tell their patients, she said.
Carlsten thinks it’s important not to put all the burden of avoiding air pollution on the individual. “We all need to be part of the community process of lobbying our elected officials and letting them know that climate change is a real problem. Climate change is very intimately linked to air pollution and we can’t continue to wait to take serious action on that.”
However, he does recommend that you familiarize yourself with air pollution patterns in your area and that you avoid spending a lot of time in places with a lot of pollution — like next to a highway. And if the authorities declare a high-pollution day, he thinks you should avoid exercising outside. “Exercise leads to a very large increase in pollution exposure because of breathing more deeply.”
To cut your risk of developing heart disease overall, Brauer suggests “making yourself as healthy as possible.”
“If you make yourself as healthy as possible, then air pollution is less likely to be the thing that takes you over the edge,” he said.
But collective action to reduce air pollution would help more, he thinks.
“If you reduce it a little bit, everybody benefits and it’s a measurable thing.”