Written by Nancy Lapid
(Reuters) – Multiple massive wildfires are raging in Los Angeles, blanketing surrounding areas in an acrid haze caused by smoke carrying noxious gases and particles that pose serious health risks.
Here’s what you need to know about the smoke risks that are likely to linger not only in Southern California but also in other wildfire regions around the world:
WHAT IS CONTAINED IN FOREST FIRE SMOKE?
More toxic than normal air pollution, wildfire smoke can linger in the air for weeks and travel hundreds of miles.
Forest fires can burn not only plant material and trees, but also cities, destroying vehicles and buildings and their contents. In addition to soil particles and biological materials, fire smoke often contains traces of chemicals, metals, plastics and other synthetic materials.
WHAT ARE THE KNOWN EFFECTS ON HEALTH?
In laboratory experiments, a certain amount of fire smoke causes more inflammation and tissue damage than the same amount of air pollution, according to Kent Pinkerton, co-director of the Center for Health and the Environment at the University of California, Davis.
Studies have linked wildfire smoke to higher rates of heart attacks and strokes and cardiac arrests, increased emergency room visits for respiratory illnesses, and weakened immune defenses. A study in Maryland identified a spike in heart and lung disease in 2023 that was linked to wildfire smoke originating up to 2,100 miles (3,380 km) away in Canada.
Forest fires have also been linked to eye irritation and skin problems.
The effects of exposure can last for years. After the Hazelwood coal mine fire in Australia in 2014, rates of heart disease remained high for two and a half years, and rates of respiratory disease remained high for five years, researchers reported.
Wildfire exposure during pregnancy is associated with pregnancy loss, low birth weight, and preterm birth. A California study found a link between wildfire exposure and cell damage in placentas in the first and second trimesters.
Canadian researchers reported that people who lived outside major cities and within 50 kilometers (31 miles) of a wildfire in the past decade had a 4.9% higher risk of lung cancer and a 10% higher risk of brain tumors.
Exposure to the 2018 California wildfires was associated with changes in cognition and brain activity six to 12 months later, likely related to stress and trauma, according to California researchers.
Data from California also show an increase in fungal infections in the months after exposure to wildfire smoke, possibly due to fungal spores in the smoke.
Greater exposure to wildfire smoke is also associated with greater odds of developing dementia, according to a study of older adults in Southern California without dementia at baseline. Even “a few really bad fire days,” with an air quality index above 200, could translate into an increased risk, said Joan Casey of the University of Washington in Seattle, who led the study.
WHAT IS UNKNOWN?
More frequent wildfires likely linked to climate change mean people will be exposed more often, and the health effects of exposure to wildfire smoke over multiple seasons are not yet clear.
“Repeated exposure 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 the fires will burn or what the smoke will contain,” Keith Bein said. from the Center for Health and the Environment at UC Davis.
Researchers are also studying the long-term effects of smoke particles in water supplies, on crops or ingested by livestock; long-term effects of smoke from urban fires; effects of wildfire exposure in utero on children’s neurological development and respiratory outcomes; and whether wildfire smoke amplifies the harmful effects of extremely hot weather.
Nutrients carried in wildfire smoke can contribute to downwind algal blooms, with implications for drinking water reservoirs and lake ecology, researchers warn.
WHAT CAN HELP MITIGATE RISKS?
Experts say it’s best to limit outdoor activities, especially strenuous sports, and wear N95 masks when fire smoke is present.
An online course with instructions on reducing outdoor and indoor fire smoke exposure is available from the US Environmental Protection Agency.
SHOULD WE REALLY WORRY?
Doug Brugge, who chairs the Department of Public Health Sciences at the UConn School of Medicine, said smoke from wildfires can be deadly. “People should … reduce their exposure, especially if they are in vulnerable populations, such as the elderly, young children or people with respiratory illnesses.”
