As wildfire seasons get longer and more intense, repeated exposure to smoke and harmful particles over time poses a greater risk to lung health, a McMaster respirologist warns. 

Kevan Mehta, a pediatric respirologist and assistant professor with McMaster University’s Department of Pediatrics, shares information about wildfire smoke, its impacts on the lungs and what you can do to protect yourself.    

What is in wildfire smoke that makes it so harmful? 

Smoke can be very different depending on what is burning. Things burning in a wildfire are different than things burning in a home. Different materials produce various types of particles, gases and harmful substances. 

When you’re close to a wildfire, you’re going to see that black smoke and encounter all sizes of harmful particles. As you get further afield from the wildfire, it is the smaller and lighter particles that are carried long distances. It is really these smaller particles that can travel long distances in the wind that we worry about, especially here in Ontario when the wildfires can be thousands of kilometres away. 

In particular, we worry about what’s called PM 2.5. These are particles that are 2.5 micrometres or smaller. Wildfire smoke can carry lots of other harmful chemicals too, such as ozone and nitrogen oxides. 

How does wildfire smoke affect the body? 

Wildfire smoke irritates the whole airway, from the nose and throat all the way down to the lungs, causing inflammation. These symptoms can be amplified further for people who have asthma or other lung issues. Children and older adults are also at a higher risk due to their unique physiology. 

PM 2.5 particles are the right size to get really deep into the lungs and have the potential of crossing into the bloodstream. Research has shown that these particles can travel through the bloodstream to the brain, kidneys, heart and other organs, having negative effects on these body parts, in addition to the lungs. 

Our lungs are quite resilient. What worries you about wildfire smoke? 

If you have one bad, short season of wildfire smoke and your lungs are pretty healthy at baseline, it’s probably not as big a deal. It’s when we start to see longer wildfire seasons and more cumulative exposure over years that I am more worried about the health impacts. 

It’s not just one or a few days in the summer anymore, as we are increasingly seeing several weeks of air quality advisories over the year. We also need to consider the severity scale of these advisories as it is not as simple as a “good’ or “bad” day of air quality. 

As a respirologist, it’s exposure to smoke and harmful particles repeatedly over long periods of time that worries me most.  

What are some ways people can protect themselves? 

As much as you can, avoid exposure to wildfire smoke. If you are in an area with smoke, try to avoid it as best you can. This can include moving as far away from the source as possible or finding places with better air quality, such as indoors. 

When there’s air advisories or really bad air quality, avoid going outside or being exposed to it as best as you can. This is always a careful balance, especially with our children, who we want doing outdoor activities and getting sunlight exposure for the many physical and mental health benefits that come with that. 

If you do have to go outside on these days, it’s important to stick with less strenuous activity. If you’re doing heavy physical activity, you will breathe harder and faster, exchanging air more frequently into your lungs and, as a result, be exposed to more harmful particles. 

I mentioned PM 2.5 particles earlier. The challenge with PM 2.5 is it can travel through many of the typical things you might wear on your face like a regular surgical mask or cloth masks. 

If you’re looking to wear a fully effective mask, even for these small particles, you would need an N95 mask to prevent those PM 2.5 particles getting into your lungs. These are the same masks that were recommended during the pandemic. I would just caution that these masks can be hard to wear for long periods of time, especially in hot weather, and may be hard for children to wear. 

What can people do to proactively make their lungs more resilient? 

There are things that you can do, primarily physical activity and exercise. In many ways, lungs are like a trainable muscle. The more you use your lungs, the better they become. 

Simply put, exercising your lungs or doing physical activity will help to improve and maintain your lung capacity. That means you’ll start from a higher point of strength if you do get anything that comes along and impacts your lungs. 

It is also important that any pre-existing health conditions, especially lung conditions, are optimally treated before encountering any stress on your lungs; these people may also need to take more specific precautions for their individual circumstances. Therefore, working with your health-care provider in advance of air advisories is very important.