What We Don’t Know About the Health Effects of Wildfire Smoke

We don’t usually think of Canada as a country that needs international aid. But in this wildfire season from hell, communities from Quebec to British Columbia are welcoming hundreds of firefighters from the U.S. and Europe with open arms.

So far this summer, a record 27 million acres in Canada have already burned, and two thirds of the roughly 900 active wildfires are still out of control. On July 18, smoke plumes drifted all the way to Atlanta, GA and 20 states now face air quality alerts. Fueled by record-breaking summer temperatures that are becoming the norm on both sides of the border, the wildfires are likely to continue until fall. For those of us living in areas hundreds of miles from the fires, how should we adapt?

The health effects of fire have been with us since the first cave men and women. Think of today’s potential harm as something like sitting around a bonfire too long. The resilience of the human body means that for most people, symptoms such as stinging eyes, coughing and minor headaches are quickly alleviated. As long as the smoke lasts no longer than a couple of days, this argues for avoiding school closures or other drastic measures that we only have in mind because of COVID-19.

We’ve met similar challenges before. Beginning in the 1970s, the U.S. and other industrialized nations have done a terrific job improving air quality. But they have done so by regulating the source of emissions in power plants and cars. Unfortunately, regulation cannot currently control the amount of smoke produced by wildfires.

The good news is that we’re not currently exposed to wildfires for as long as residents of developing countries are to smog, which makes continued emissions from factories and automobiles the more immediate threat to public health in cities worldwide.

Read More: Wildfire Smoke Is the New Normal

But caution is in order. Right now, too few researchers are studying wildfire smoke from generation to inhalation. We just don’t know enough yet to fashion effective public policy.

While at first glance natural smoke from burning wood would seem less dangerous than industrial pollution, the size and composition of the organic particles make them more likely to enter the bloodstream.

We’re still in the early stages of understanding the consequences of that, especially since these immense plumes of smoke—some of which can be seen from space— vary in content and density, depending on the vegetation they burn. We can’t always predict with total accuracy how high and far the smoke will travel. We simply don’t know what’s in the smoke once it mixes with air and travels to cities with their own sources of pollution. And we’re only beginning to grasp what it’s health effects might be, especially on young children, the elderly, and those with pre-existing lung and eye conditions.

So much about this remains a mystery. The fact that natural fire didn’t kill pre-historic humans is not ultimately very comforting because their life spans were only 30 years or so. What are the long-term effects of exposure to smoke? We know that people who live close to wildfires and suffer from pre-existing lung conditions have higher morbidity rates. But we have little sense of how far from the fire is far enough and how many days of exposure the body can handle. This is especially concerning given how early wildfire season is now starting, thanks to climate change. And we simply don’t know how well air quality standards for industrial pollution apply to wildfire smoke. What happens when the smoke seeps indoors, as it always does after a couple of days? How much should we ventilate? We don’t know that, either.

In an ideal world, we would have prediction models able to forecast the arrival of haze with the same accuracy as hurricanes. But as a result of the cumulative uncertainties in fire modeling, climate prediction, and physiological responses, the answer is not there yet.

The good news is that these more frequent wildfires in Canada, the American West, and other parts of the world have ignited new research that can help us understand the exact composition of the pollutants, the potentially carcinogenic effects, and how our buildings protect us—or don’t. Once we have our arms around the problem scientifically and develop better sensors and atmospheric models, mitigation efforts will proceed more smoothly.

Expanding controlled burns, which were used effectively by Aborigines in Australia, First Nations in Canada, and Native Americans in the U.S. for centuries, will help address this problem. Those burns, if properly supervised, produce smoke plumes of reduced toxicity and lower the risk of mega-fires that more often spread smoke to cities hundreds of miles away.

In the meantime, we can learn something from COVID-19: When in doubt, take reasonable precautions. Which is why weather forecasters who tell us to bring umbrellas when it’s raining might start reminding us not to forget our N-95 masks when it’s smoky outside.