Some wildfire suppressants contain heavy metals and could contaminate the environment
PressPacs October 30, 2024
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“Metals in Wildfire Suppressants”
Environmental Science & Technology Letters

In fire-prone areas, water isn’t the only thing used to quell blazes. Wildland firefighters also apply chemical or synthetic suppressants. Researchers reporting in ACS’ Environmental Science & Technology Letters explored whether these suppressants could be a source of elevated metal levels sometimes found in waterways after wildfires are extinguished. Several products they investigated contained high levels of at least one metal, including chromium and cadmium, and could contribute to post-fire increases in the environment.

“Wildfires are associated with the release of toxic heavy metals to the environment, but until now, it was assumed that these metals came from natural sources like soil,” says Daniel McCurry, principal investigator of the study. “We now know that fire retardants may contribute to these metal releases.”

Wildfire suppressant products, which are intended to inhibit fire activity before and after water evaporates, include fire retardants, water enhancers and foams. As wildfires have become more frequent and severe, larger volumes of water along with chemical and synthetic suppressants — sprayed from the ground and dropped from planes — have been required to extinguish them. Although manufacturers identify most of the active ingredients in suppressants, some components are proprietary. In addition, previous researchers have observed increased concentrations of potentially toxic metals in soil and streams after wildfires. So, McCurry and colleagues at the University of Southern California wondered if the suppressants contain metals and could contaminate the environment.

The researchers tested samples from 14 fire suppression products sold by commercial retailers. They analyzed samples for 10 metals that have known toxicity or are regulated by the U.S. Environmental Protection Agency (EPA). Every product contained at least one metal with a concentration that exceeded the EPA’s Maximum Contaminant Level regulations for drinking water. In particular, the two suppression products classified as fire retardants contained eight metals (chromium, cadmium, arsenic, lead, vanadium, manganese, antimony and thallium) that greatly exceeded the EPA’s drinking water regulations. And one of the retardants exceeded California’s hazardous waste regulations for three of those metals. The researchers say these results indicate the potential for fire retardants to contaminate the aquatic environment and potentially drinking water, if these products enter bodies of waters.

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