Explanation: Smoke from raging forest fires can harm health


A helicopter flies near smoke billowing from a forest fire on the border with Slovenia seen from Rupa, Italy, July 20, 2022. REUTERS/Borut Zivulovic/File Photo

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July 21 (Reuters) – Wildfires are increasing in frequency and intensity in many countries, spreading smoke that contains harmful gases, chemicals and particles and poses serious health risks. More toxic than air pollution, wildfire smoke can linger in the air for weeks and travel hundreds of miles.

Wildfires “burn not only plant material and trees, but also cities, completely destroying vehicles and buildings and their contents,” said Kent Pinkerton, director of the Center for Health and the Environment at the University of California to Davis.

In addition to soil particles and biological materials, smoke from wildfires often contains traces of metals, plastics and other synthetic materials.

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Laboratory experiments have shown that a given amount of wildfire smoke causes more inflammation and tissue damage than the same amount of air pollution, Pinkerton said.

Studies in humans have linked wildfire smoke to higher rates of heart attacks, strokes, and cardiac arrests; increased emergency room visits for asthma and other respiratory conditions; and weakened immune defenses.

Some increased transmission of COVID-19 has been attributed to the spread of the virus on particles in smoke from wildfires. Exposure to wildfires during pregnancy has been associated with pregnancy loss, low birth weight, and premature delivery. Wildfires have also been linked to eye irritation and itchy skin, rashes and other dermatological problems.

Studies of firefighters have documented higher cancer risks in these highly exposed workers, but less is known about cancer risks to the public.

Canadian researchers reported in May in The Lancet Planetary Health that people who lived outside major cities and within 50 kilometers (31 miles) of a wildfire in the last decade had a risk 4 .9% higher risk of lung cancer and a 10% higher risk of brain tumors compared to people not exposed to wildfires.

At UC Davis, researchers are tracking cancer rates among people exposed to the 2018 Campfire, the most destructive wildfire in California history.


More frequent wildfires mean people will be exposed more often, but studies have only just begun on the health effects of exposure to wildfire smoke over multiple seasons.

“Repeated exposure, summer after summer after summer, is more likely to cause disease, but it’s hard to make predictions because it’s hard to tell how many fires people will be exposed to, how long fires will burn or what the smoke will contain,” said Keith Bein of the UC Davis Center for Health and Environment.

Other current lines of research include the long-term effects of smoke particles in water supplies, on crops, or ingested by livestock; the long-term effects of smoke from urban wildfires; the effects of in utero exposure to wildfires on neurodevelopment and respiratory outcomes in children and whether wildfire smoke amplifies the adverse effects of extremely hot weather.


An online course with instructions for reducing outdoor and indoor exposure to wildfire smoke is available from the US Environmental Protection Agency.

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Reporting by Nancy Lapid Editing by Michele Gershberg and Frances Kerry

Our standards: The Thomson Reuters Trust Principles.


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