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Wildfire smoke could be to blame for an increase in cases of pink eye: experts


If you’ve been feeling a burning in your eyes after spending time outside sometime in the last few months, it might be more common than you think — according to some experts, the poor air quality caused by raging wildfires across Canada is affecting more than just our lungs.

Poor air quality caused by wildfire smoke could bring more cases of conjunctivitis and eye irritation than usual this year, experts warn.

“I've had a lot of patients who are just complaining of eye irritation, or those who already have dry eye, that are really finding that their symptoms are sort of acting up,” Mili Roy, an actively practicing ophthalmologist in Oakville, Ontario, told in a phone interview.

Roy, who is also an assistant professor in the department of ophthalmology at the University of Toronto, said that earlier in the spring, there were more patients coming in with their seasonal allergies “being much worse because of climate change.

“Now that we're sort of deeper into summer, we're seeing more people with just irritated eyes,” she said. “But particularly on the poor air quality days.”

The conjunctiva is a layer of tissue covering the front of the eyeball, and inflammation of that layer is called conjunctivitis. When conjunctivitis is caused by a viral infection, it’s more commonly referred to as ‘pink eye’, but conjunctivitis can also be caused by chemicals, allergens or other irritants in the air.

“What we are seeing is that the wildfire smoke, it creates an external irritant to the eye,” Roy said. “So that produces a form of what we call conjunctivitis due to that external irritation. And the other thing that happens with the wildfire smoke is with all the toxins that are in the air, it sort of acts as a bit of an allergen as well. So it can cause a little bit of an allergic conjunctivitis (as well).”

The wildfires have caused record-breaking levels of poor air quality over the last few weeks alone.

Last week, Toronto’s air quality was the worst in the world according to a Swiss air quality tracker. Only a few days before, Montreal had the worst air quality in the world, all due to smog produced by wildfires in northern Quebec.

When a person is exposed to irritants in the air, they may feel those effects not just in their lungs, but in their eyes.

“It tends to cause burning of the eyes and tearing. Sometimes it can cause some light sensitivity,” Roy said. "More rarely, it might cause you a little bit of thin or watery discharge, but nothing that's really sort of thick or purulent, which is more typical of an infectious conjunctivitis, which is your classic pink eye.”

It’s no surprise that wildfire smoke can be a source of eye irritation, according to Dan Riskin, CTV News' Science and Technology Specialist.

“Any kind of smoke, from cigarettes to car exhaust can cause severe irritation of the eyes,” he told in an email.

An Australian study published last year reviewed the effects of wildfire smoke and air pollution on the eyes and found that there was “strong evidence that wildfire smoke and other air pollution sources have harmful effects on ocular surface.”

“After a wildfire near Canberra, 73 per cent of people there reported experiencing eye irritation,” Riskin said, a figure which he added was five times “higher than places without wildfires.”

Researchers noted that we still don’t know what long-term damage to the eyes may come from wildfire smoke.

One of the difficulties in preventing this eye irritation is that there’s no clear measure yet for how poor the air quality needs to be or how long a person needs spend outside in the air in order for them to be at risk of eye irritation.

It differs from person to person, Roy said.

“One of the things that tends to make some people more sensitive are those who have a dry eye to begin with,” she said. “And dry eye is a really common condition. So dry eye will tend to just increase the sensitivity to external irritants, in general, and certainly including things like this exposure to wildfire smoke.”

Marisa Sit, an ophthalmologist in the Comprehensive Ophthalmology Unit at the Donald K. Johnson Eye Institute, which is part of the University Health Network, told that there’s “really no time stamp that you could put on it,” in terms of how to predict if and when your eyes might start hurting while outside on a day with poor air quality.

“It really varies between individuals and their kind of pre-existing condition of their eyes,” she said in a phone interview.

She noted that she’s a specialist and thus not the first point of contact that a patient with eye irritation would have, but added that she has heard from colleagues that there have been more patients coming in on days when the air quality is particularly poor.

“People do complain that when they're outside, that their eyes are more irritated, just as their throat is more irritated, their breathing seems to be irritated, that kind of thing,” she said.


The majority of ways to deal with eye irritation caused by poor air quality are largely “common sense measures,” Roy said.

If you pay attention to your symptoms when they are just starting, heading inside can head off those symptoms worsening.

“Try to get out of out of that environment as much as possible into an environment with maybe filtered air indoors,” she said. And the other thing is, sometimes it's just a relief to lubricate the eyes with something like preservative-free artificial teardrops that just helped to sort of dilute the surface irritants that are causing the symptoms in the first place.”

Sit, who is also a lecturer at the University of Toronto in the Department of Ophthalmology and Vision Sciences, echoed the recommendation, adding that artificial tears can “help soothe your eyes” and “flush away some of the irritants.”

She said that cool compresses may also soothe some irritation.

Many people aren’t able to simply go inside when there’s poor air quality, such as those who have outdoor jobs. Those who know they’re going to be outside for long hours on days with a worrying air quality index could prepare to handle eye irritation by having protective eyewear on hand.

“If you have to be outside and you're working, maybe goggles would be a good idea, if you're concerned about the outside air quality,” Sit said.

Depending on the person, their susceptibility to eye irritation, and the type of air quality they were exposed to, the duration of the irritation can range.

“If the eye had become quite irritated to begin with, it can take a little bit of extra time to settle down,” Roy said. “We’re probably talking several hours rather than days, that’s probably the most realistic estimate.”


This issue goes far beyond eye irritation, experts say, as poor air quality comes with a range of health issues.

“As air quality becomes worse then we're concerned about long-term risk to our lungs and things like that,” Sit said. “And similarly, I think we're also concerned about long-term risk of chronic irritation in your eyes.”

Roy said the core of the issue lies in our need to address climate change.

“The climate crisis is the single greatest health crisis on the planet, hands down,” she said. “And intertwined with that is this massive health crisis due to air pollution and the toxins we're breathing. And the common root there is that fossil fossil fuels are fuelling both.”

She pointed out that this means that the solutions can be found in the problem itself.

“(If) we’re able to rapidly transition off fossil fuels, and we have so many better and cheaper options, we will have massive public health benefits around the world,” she said.

“This week alone, as a planetary whole, we just set two planetary records for the hottest days on Earth that we have ever seen. And we know that the warm temperatures are directly linked with forest fire activity. So I'm deeply concerned. And as I say, really what we're seeing in ophthalmology, in a sense, is just the tip of the iceberg.” Top Stories

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