By Nancy Lapid
(Reuters) - Multiple massive wildfires are raging in Los Angeles, blanketing the surrounding regions under a pungent haze caused by smoke carrying noxious gases and particulate matter that pose serious health risks.
Here is what you need to know about the risks of the smoke that is likely to linger not only in southern California but in other regions around the world where wildfires are burning:
WHAT IS CONTAINED IN WILDFIRE SMOKE?
More toxic than normal air pollution, wildfire smoke can linger in the air for weeks and travel hundreds of miles.
Wildfires can burn not only vegetative materials and trees but also cities, destroying vehicles and buildings and their contents. Along with particles of soil and biological materials, wildfire smoke often contains traces of chemicals, metals, plastics and other synthetic materials.
WHAT ARE THE KNOWN HEALTH EFFECTS?
In laboratory experiments, a given amount of wildfire 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 with higher rates of heart attacks, strokes, and cardiac arrests, increases in emergency room visits for respiratory conditions, and weakened immune defenses. A study in Maryland identified a spike in heart and lung illnesses in 2023 that was associated with wildfire smoke originating up to 2,100 miles (3,380 km) away in Canada.
Wildfires also have been linked with eye irritation and skin problems.
The effects of exposure can persist for years. After Australia's 2014 Hazelwood Coal Mine fire, rates of heart disease remained elevated for two and a half years and respiratory illnesses for five years, researchers have reported.
Wildfire exposure in pregnancy has been associated with pregnancy loss, low birth weight, and preterm delivery. A study from California found a link between wildfire exposure and cellular damage in first- and second-trimester placentas.
Canadian researchers have reported that people who lived outside of 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 Camp Fire in California was linked to changes in cognition and brain activity six to 12 months later, possibly related to stress and trauma, according to California researchers.
Data from California also show an increase in fungal infections in the months following wildfire smoke exposure, likely due to fungal spores in the smoke.
Higher exposure to wildfire smoke is also associated with higher odds of developing dementia, according to a study of southern California seniors without dementia at baseline. Even “a few really severe wildfire smoke days,” with the Air Quality Index over 200, could translate into 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 wildfire smoke exposure over multiple seasons are not yet clear.
"Repeated exposure is more likely to cause diseases, but it is hard to make predictions because it is hard to say how many fires people will be exposed to, how long the fires will burn, or what the smoke will contain," said Keith Bein of the Center for Health and Environment at UC Davis.
Researchers are also looking into the long-term effects of smoke particles in water supplies, on crops or ingested by livestock; the long-term effects of urban wildfire smoke; the effects of wildfire exposure in utero on children's neurological development and respiratory outcomes; and whether wildfire smoke amplifies the adverse effects of extremely hot weather.
Nutrients carried in wildfire smoke may contribute to downwind algal blooms, which has implications for drinking water reservoirs and lake ecology, researchers warn.
WHAT CAN HELP MITIGATE THE RISKS?
Experts say it is best to limit outdoor activities, especially strenuous sports, and to wear N95 masks when wildfire smoke is present.
An online course with instructions for reducing outdoor and indoor exposure to wildfire smoke is available from the U.S. Environmental Protection Agency.
DO WE REALLY NEED TO WORRY?
Doug Brugge, who chairs the Department of Public Health Sciences at UConn School of Medicine, said wildfire smoke can be deadly. "People should... reduce their exposure, especially if they are in a vulnerable population, such as the elderly, young children or people with respiratory diseases."