In addition to hearts and lungs, wildfire smoke may mess with the human brain, emerging research suggests.
Fine particulate matter carried in wildfire smoke can enter the brain via the bloodstream, causing inflammation and oxidative stress, a condition resulting from too many cell-damaging molecules called free radicals and not enough antioxidants to mop them up, one theory holds.
Recently, scientists have linked exposure to wildfire smoke to increased risks for impaired cognitive function, memory loss, greater odds of being
diagnosed with dementia
and an increase in
emergency department visits
for anxiety, depression, psychotic episodes and other mental-health problems.
Plumes of smoke from Prairie wildfires that have forced the evacuation of thousands of people from their homes led to air quality advisories issued for large swaths of the country Friday, with Environment Canada messages covering British Columbia, the Prairies and most of Ontario and Quebec, the
Montreal Gazette reported.
More toxic than other sources of pollution, wildfire smoke can cause a range of health effects, from mild coughs, itchy eyes and headaches to dizziness, wheezing, chest pains, asthma attacks, shortness of breath and heart palpitations.
And when heat and poor air quality combine, the health impacts are reached that much sooner, said Dr. Anna Gunz, a pediatric intensive care doctor at Children’s Hospital, London Health Sciences Centre and associate professor at Western University’s Schulich School of Medicine & Dentistry.
While those at the doorstep of fires are most vulnerable, the fine particulates in wildfire smoke can travel 1,000 kilometres or more.
The National Post spoke to Gunz to help unpack how wildfire smoke can impact physical and mental health. This conversation has been edited and condensed for clarity and length.
What makes wildfire smoke particularly risky for human health?
We have over 40 years of air pollution health data and so some of this is grounded in the same principles.
We love the smell of campfires. But even the smoke that we breathe by a campfire contains lots of particulates that are actually really bad for us. It’s not stuff that we’re supposed to be breathing.
When we think about wildfires, it’s not just wood that’s been cut from trees that you maybe know. It’s everything else that’s burning — pesticides, herbicides, metals. Even allergens and fungus.
Because it moves so far, you don’t need to be right next to a wildfire to be affected. It’s high concentrations for shorter periods of time, but it is ubiquitous. Part of the problem with being away from the wildfire is that people don’t necessarily realize the air might be bad. It can be really deceiving.
And then you have the people who are near the fires who’ve been evacuated or are at risk of evacuation. And so, the fear, the trauma, the risks of PTSD and other emotional things. People are stressed. I’m always thinking about children and women and those who are vulnerable (such as) Indigenous folks who are disproportionately displaced by wildfires every year and removed from their community.
What are the immediate health effects from exposure to wildfire smoke?
The first contact we have with smoke is our eyes, our mucus membranes, and our upper airways.
If we think about breathing in smoke and where it goes next, it goes to our large airways and those are the airways that are affected by asthma. So, certainly the people at highest risk of becoming ill, or more ill and coming into hospital, are anyone with puffers. Asthma, absolutely. But people with COPD (chronic obstructive pulmonary disease), cystic fibrosis and lung issues are going to have a harder time breathing.
Your eyes and your upper airways and mucus membranes are going to see the larger particles of irritants, and they’re going to start reacting to those larger particles.
And then the things we can’t smell or see, or taste are these small micro-particles, and that’s what gets absorbed through our lungs and into our blood stream. And it causes a huge inflammation in the body. That’s at least the biological reason why we think that the other things we see in terms of heart and brain health are noted.
Once inside the blood, how do micro-particles trigger something like a heart attack?
There’s been a lot of research looking at trying to understand the mechanisms in the pathways in your blood vessels that could lead to this.
Our blood vessels travel in our brains and in our hearts. Even though we think about heart attacks and stroke differently — they present very differently — ultimately what is happening is your small blood vessels that are either supplying your heart or your brain can become clogged.
The lining of our blood vessels is called the endothelium, and it’s this really complex place where there are these active living cells. (Endothelial function helps control how well blood is balanced in terms of clotting and how thin it is.)
One theorized mechanism is that (exposure to wildfire smoke) activates different inflammatory pathways that affect your endothelium.
There is less long-term neural data right now around wildfires. (However, one 10-year study of more than one million people in southern California found persistent exposures to wildfire smoke increased the risk of dementia more than other forms of air pollution. Another group found that wildfire smoke exposure during the 2020 California wildfires was associated with higher odds of subsequent emergency visits for mental health conditions. Inhaled particulate matter, the researchers said, can reach the brain, potentially causing inflammation, oxidative stress and damage to the brain’s blood vessels.)
Why is excessive heat plus smoke particularly dangerous?
When it’s hot, you also get secondary air pollutants, like ozone. The heat and the air interact to create more pollution.
What can people do to reduce their health risks?
Anyone with a chronic illness, the elderly and children are always at higher risk.
If it’s smoky outside, shut the windows, turn on the AC. Know what the air quality is and understand that it changes at different times of the day.
If you’re going to be outside, try to plan according to air quality (people can check the federal
Air Quality Health Index
or special air quality statements or advisories for their area). If you’re going to be doing something that has more exertion and you’re going to be breathing faster, like exercise, better to do that when the air quality is better.
An N95 mask can help filter a number of these particles.
If you know some kids (with asthma or other lung conditions) are going to be triggered (by the smoke), make sure that the care for the lungs is really under control heading into wildfire season. (ER visits for
asthma spiked across Ontario during the 2023 Canadian wildfires.)
For people who are living near evacuation zones where they know this happens and they talk about “go bags,” it’s important to think about medications. Ask your doctor to prescribe in such a way that you can have stashes of medicines in your “go bag” so that if you’re evacuated you still have access to them.
National Post
Our website is the place for the latest breaking news, exclusive scoops, longreads and provocative commentary. Please bookmark nationalpost.com and sign up for our newsletters here.
