As large wildfires have become regular occurrences in Canada, some scientists warn that repeated exposure to the air pollution they produce could pose health risks. Here’s what you need to know about the risks and how to protect yourself.

What are the short- and long-term health risks posed by air pollution from wildfires?

In the short term, exposure to wildfire smoke can irritate the eyes and throat and cause runny noses, wheezing, phlegm production and headaches, according to Luisa Giles, an assistant professor in the school of kinesiology at the University of Fraser Valley, who focuses on the health effects of air pollution. It can cause some people to experience difficulty breathing, chest pain, dizziness, heart palpitations and impaired lung function, and can exacerbate respiratory and cardiovascular illnesses, she said.

There’s minimal research on any long-term health effects. But even so, Dr. Giles said, “an absence of evidence does not always indicate an absence of effect, therefore, it’s still recommended that individuals are cautious and aim to reduce their air pollution exposure where possible.”

Some initial research suggests exposure to air pollution from wildfires may be linked to increased risk of a range of health outcomes, including cancer and death from heart disease in older adults, and potentially dementia.

How can you tell whether it’s safe to spend time outdoors?

Dr. Giles said a good place to start is checking the Air Quality Health Index for your area. This index is a scale from 1 to 10+ that provides an indicator of the health risk related to air quality and can be found on the Environment Canada website or provincial environment ministry sites. Alternatively, she suggests setting up Canada’s WeatherCAN app, which can alert you about what to do when the air quality is poor.

Should you exercise when air quality is poor?

When it’s smoky outside, exercising indoors is always a good first option, says Dr. Giles. Make sure, though, that your gym has its windows closed and is using HEPA filter, she advises. If the windows are open, or there isn’t a HEPA filter, then exercising indoors would be very similar to doing so outside. If you are exercising or spending time outdoors, however, you’ll still want to try and minimize exposure to air pollution, Dr. Giles says. You can do so, for example, by checking the Air Quality Health Index, and planning your outdoor activities to avoid times of the day when air pollution is worst.

What can you do you protect yourself from health effects of wildfires?

Pay attention to your exposure throughout the course of the day, and try to reduce it by, for example, keeping your windows closed (though try to not overheat) and using a HEPA filter if you have the means, Dr. Giles said.

Some areas may provide clean air shelters. These are libraries, community centres or schools where people can seek relief from smoky air. Health Canada published guidelines in 2020 for creating and managing clean air shelters during wildfire smoke events, which include ensuring they have HVAC systems that can filter fine particulate matter and are connected to an emergency power supply in case of power outages.

Dr. Giles suggests you could also use a furnace filter with a higher MERV rating, such as 12 or 13, and keep your furnace fan running. Another option, she said, is wearing an N95 respirator if you are running errands or exercising wherever air quality is poor.

Chris Carlsten, head of respiratory medicine at the University of British Columbia and director of Vancouver Coastal Health’s Legacy for Airway Health program, said he, too, strongly recommends the use of air filters. This can be in the form of a small system in your bedroom, for example, or a large system for an entire building. Much of the advice on improving indoor air quality, such as using HEPA filters and regularly cleaning or changing filters on HVAC systems, will sound familiar after the past few years of COVID-19. (Though during wildfires, it’s not advisable to keep windows open.)

When it comes to coping with the short-term health risks of exposure to wildfire smoke, it’s important to keep in mind that everyone will react differently, Dr. Carlsten said. Some people can exercise outside and not be bothered at all by it, while their peers don’t tolerate it well. So while those with respiratory or cardiovascular diseases ought to take greater precautions, he suggests letting your experience be your guide.

He also recommends speaking with your health care provider about any concerns.

The Globe and Mail, June 7, 2023