How Wildfire Smoke and Retardant Sludge Affect Human Health and the Environment

While flames may pose the most visible danger from wildfires, experts say the smoke and fire-retardant sludge can have lasting effects on human health and the environment.

New research has linked exposure to wildfire smoke to higher rates of dementia, reproductive health problems, and lung and heart disease, and Forest Service employees say the iconic red fire-retardant goo dropped from airplanes has been linked to the deaths of thousands of fish.

“There are hundreds of gases that are emitted from wildfire smoke, some of them in very, very small amounts,” said Rebecca Hornbrook, a scientist at the National Center for Atmospheric Research. “Some, like carbon monoxide, carbon dioxide, and nitrogen oxides, are emitted in larger amounts, but some of those gases in smaller amounts are actually more toxic.”

Short-term effects of wildfire smoke

“Everyone can be affected by wildfire smoke,” said Colleen Reid, an associate professor at the University of Colorado Boulder who studies the health impacts of wildfire smoke. “… We see an increase in health impacts within a day of high smoke exposure.”

Normal symptoms when smoke is heavy in the air include coughing, shortness of breath, headache, fatigue, chest pain and itchy, watery eyes, Reid said. Emergency room visits and hospital admissions for breathing problems also increase when smoke is active.

According to Reid, mild symptoms often disappear within a day or two after the smoke clears from the area.

In addition to smoke, wildfires also leave behind ash that can irritate the lungs, eyes, nose, and skin, according to the Centers for Disease Control and Prevention.

According to the CDC, as residents clean up areas affected by a wildfire, they should wear protective clothing and eyewear and wash away any ash that comes into contact with their skin, eyes, or mouth as soon as possible.

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“We know a lot about the short-term health effects of exposure to wildfire smoke, but we know less about the long-term effects,” Reid said.

According to Reid and David González, associate professor of environmental health sciences at the University of California, Berkeley, who is collaborating with researchers in Colorado to determine the long-term impacts of wildfire smoke exposure, recent studies have linked wildfire smoke exposure to increased cases of influenza, reduced lung function, and higher rates of depression, anxiety, and dementia.

The increase in flu cases was first noticed after a bad bushfire season several years ago, and researchers believe exposure to bushfire smoke may have made people’s lungs more susceptible to infection when exposed to the virus, Reid said.

According to González, wildfires also impact cardiovascular health (smoking can trigger heart attacks and strokes, worsen heart failure, cause abnormal heart rhythms, or exacerbate pre-existing heart disease) and reproductive health (smoking increases the risk of birth defects, miscarriage, and infertility in both men and women).

Reid said people can begin to notice health effects, both short- and long-term, after just one day of high-level smoke exposure.

Smoke from wildfires further away can sometimes have more serious health impacts on communities than fires closer to home, according to a recent study from Colorado State University.

Researchers believe this is more likely due to changes in behavior than the distance of the smoke itself, Reid said. People who see the fire or smell the smoke may be more likely to take proactive, protective measures than people farther away from the fire site.

While the distance smoke travels depends on wind, weather and how high it is in the atmosphere, researchers are seeing increased air pollution around the world, even in places where wildfires are rare or nonexistent, González said. The smoke can travel to distant states or even countries.

“If there is smoke, try to stay indoors with windows and doors closed,” Reid said. “Wear an N95 or KN95 mask when you are outdoors and try to schedule your outdoor activities when the air is cleaner.”

Reid said people should use air purifiers indoors and replace filters on air purifiers and air conditioners frequently: Smoke can clog filters and prevent them from working as effectively.

“There’s still a lot of work to be done here,” González said. “This is not the end of the story.”

Health and environmental impacts of flame retardants

According to former U.S. Forest Service employee Andy Stahl, wildfire retardants are about 85 percent water, 10 percent ammonium phosphate fertilizer, and 5 percent minor ingredients, including a dye that helps pilots see where the manure has already been spilled.

“It’s harmful to the environment when it’s dumped into water because ammonium phosphate converts to ammonia, and ammonia is highly toxic to fish,” Stahl said. The former U.S. Forest Service employee is now executive director of Forest Service Employees for Environmental Ethics. A single drop of flame retardant in a stream can be lethal to fish and other aquatic organisms.

According to the U.S. Forest Service, under “very specific conditions,” the fertilizer could poison animals that ate contaminated crops or drank water containing retardants.

However, as long as there are no people under the retardant as it falls, the mixture has shown no signs of long-term impacts on human health, Stahl said.

According to the U.S. Forest Service, ammonia-based flame retardant will burn if it gets into cuts or scrapes, or if it comes in contact with cracked or burned skin. People should wash skin that comes in contact with the slurry with mild soap and water before using hand cream to avoid dryness and cracking.

If retardant falls on homes, residents should clean the building as soon as possible, Boulder fire officials said. However, homes covered in retardant should be safe to stay until they can be cleaned.

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