Some forest fire suppressants contain heavy metals and can pollute the environment

In fire-prone areas, water is not the only thing used to extinguish a fire. Wildland firefighters also use chemical or synthetic suppressants. Researchers report in Environmental Science & Technology Letters investigated whether these suppressors could be the source of high levels of the metal that are sometimes found in waterways after wildfires are extinguished.

Several products they studied contained high levels of at least one metallicincluding chromium and cadmium, and may contribute to environmental post-fire growth.

“Forest fires have been linked to the release of toxic heavy metals into the environment, but until now it was assumed that these metals originated; natural sources like soil,” says Daniel McCurry, lead researcher on the study. “We now know that fire retardants can contribute to these metal releases.”

Suppressants designed to stop wildfires fire activity before and after water evaporates, includes fire retardants, water enhancers and foams. As wildfires have become more frequent and severe, greater volumes of water have been required to extinguish them, along with chemical and synthetic suppressants sprayed from the ground and dropped from aircraft.

Although manufacturers identify most active ingredients in suppressants, some ingredients are proprietary. In addition, previous researchers have observed increases in concentrations of potentially toxic metals in soil and streams following wildfires.

So McCurry and colleagues at the University of Southern California wondered whether the suppressants contained metals and could contaminate the environment.

The researchers tested samples of 14 commercially available fire suppression products. They analyzed samples for 10 metals that have known toxicity or are regulated by the US Environmental Protection Agency (EPA).

Each product contained at least one metal whose concentration exceeded the EPA’s maximum contaminant level regulations for drinking water.

Specifically, two suppression products classified as firefighting contained eight metals (chromium, cadmium, arsenic, lead, vanadium, manganese, antimony, and thallium) that significantly exceeded EPA drinking water guidelines. And one delayer exceeded California’s hazardous waste regulations for three of those metals.

The researchers say these results show that fire retardants can pollute aquatic environment and potentially drinking water if these products enter water bodies.

The volume of fire-extinguishing materials has decreased forest fires In the US between 2009 and 2021, researchers found that the total amount of metals used varied from year to year, but generally increased over time. And in one Southern California wildfire, they estimate that increased cadmium concentrations in a nearby stream could be explained by 31% of the fire retardant used to contain the fire.

They say these results suggest that firefighting activities may contribute to increased levels of the metal in the environment, but more work is needed to determine potential risks to people and humans. environmental health.