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This is a common sight during major fires in the West. The plane lowered over a smoldering ridge, releasing ribbons of flame retardant that painted the hillside bright pink. Onlookers cheer at the display of firefighting power.
The U.S. Forest Service and other agencies drop tens of millions of gallons of fire retardant (primarily an ammonium phosphate-based slurry called Phoscheck) around wildfires each year to cover vegetation and slow the spread of flames. are.
But a new study by USC researchers found that the popular variety contains toxic metals, and the use of flame retardants has added 850,000 pounds of these chemicals into the environment since 2009. It is estimated that it has been released. The results suggest that the ecological effects of flame retardant use merit further study. And it’s probably worth finding a cleaner product, said Daniel McCurry, an associate professor of civil and environmental engineering at USC and one of the study authors.
The discovery adds to environmentalists’ long-standing concerns about the effects of retarder drops. But fire officials say the benefits of the practice save lives, minimize the spread of fires and protect ecosystems outweigh the potential harm.
This debate is expected to intensify as wildfires increase in size and severity, in part due to climate change.
“There is a clear trend that the frequency and intensity of wildfires is increasing, and to my knowledge the management of these wildfires will continue to include aerial firefighting for the foreseeable future,” McCurry said. spoke.
Orange County Fire Chief Brian Fennessy acknowledged there are drawbacks to using flame retardants, including harm to aquatic life if they spill into waterways. But when it comes to fighting wildfires, there is simply no substitute for flame retardants, he said.
The viscous material is more effective than water, sticking to plants and maintaining their slowing properties even when dry. If crews can’t use it, “the fire is going to get bigger. That’s the basic answer,” he said.
“I think there’s a trade-off and a balance there. Each situation is a little different, but those considerations need to be considered and need to be discussed,” Fennessy said.
In the USC study published in Environmental Science & Technology Letters, McCurry and his fellow researchers tested 14 different fire extinguishing agents. All were purchased on the open market as manufacturers refused to provide samples, he said.
Each contained at least eight heavy metals. One in particular, Phos-Chek LC-95W, contains “potentially alarming” concentrations of several metals, including chromium, cadmium, and vanadium, making the substance subject to federal and California regulations. It could be classified as hazardous waste under regulations, he added.
Chronic exposure to these metals has been linked to cancer, kidney and liver disease in humans, but the potential negative effects on the environment are even more concerning, especially if flame retardants enter waterways. That’s likely, he said.
McCurry explained that the flame retardant his team tested was a colorless version of the bright pink Foscek that is jettisoned from aircraft. The pink LC-95A is not available for consumer purchase.
Perimeter Solutions, which manufactures Phos-Chek, said in a statement that the products are chemically different and that LC-95W has never been used in aviation applications. All Phoscheck flame retardants used in aerial firefighting operations must be fully certified by the Forest Service and require extensive testing to meet stringent safety standards, the statement said.
The Forest Service said it has used the Foscheck LC-95W for aerial firefighting operations, although infrequently. The formulation was tested in the air and on the ground after passing multiple safety tests, including a toxicity profile leaching protocol developed by the Environmental Protection Agency to simulate how much of a material’s toxic components would be released into a landfill. It has been approved for both uses, the agency said.
The discovery provides new clues to a phenomenon geochemists have long documented: heavy metal concentrations in streams and rivers tend to spike after nearby wildfires. For example, after a fire in the Angeles National Forest in 2009, researchers measured cadmium concentrations up to 1,000 times higher in Arroyo Seco.
“There are many hypotheses about what the source of these metals is, and this adds a new dimension,” said Josh West, a professor of geoscience and environmental studies at the University of Southern California. West was not involved in McCurry’s research, but provided feedback before the paper was published.
More research is needed to learn how much retardants leach into waterways and how much they contribute to elevated metal levels, West said. It could be one of several sources. His research suggests that metals in air pollution are deposited on vegetation and released into soil and waterways when that vegetation burns.
McCurry’s team is working to learn more about whether the metals in flame retardants leach into groundwater or runoff into streams and rivers. One method involves sampling soil from the San Gabriel Mountains, applying Phoscheck, conducting controlled combustion in the lab, and using a student-built rainfall simulator to see how metals move. Includes modeling.
They are also trying to dig into the source of heavy metal concentrations in rivers after wildfires by using unique isotopic fingerprints to link chemicals to flame retardants or other sources.
And to test the Phoscheck formulation, which is not commercially available, his researchers visited incineration sites, including those charred by the Post Fire near Gorman and last year’s Highland Fire near Aguanga, to test the flame retardant. A sample of the sprayed soil was taken. The plan is to test the metal content.
Andy Stahl, executive director of the environmental group Forest Service Employees for Environmental Ethics, said the study reinforces concerns about heavy metal concentrations in Foscek, which until recently were supported by circumstantial evidence. . For example, an air tanker base in Washington was accused in 2016 by the state Department of Ecology of violating limits for cadmium, chromium, and vanadium in its waste discharge permit. The Forest Service report said it could not rule out the possibility that the flame retardant hosed down from fire planes contained heavy metal impurities.
Stahl’s group has sued the Forest Service multiple times over the use of flame retardants dating back to 2003, resulting in the Forest Service establishing buffer zones around vulnerable species habitat and waterways and public access. They agreed to refrain from dropping flame retardants unless there was a risk to safety.
The nonprofit filed a lawsuit in U.S. District Court in Montana in 2022 after the Forest Service reported dropping more than 1 million gallons of fire retardant into these restricted areas from 2012 to 2019. .
As part of the lawsuit, the nonprofit group asked for a moratorium on the agency’s use of airborne flame retardants until it receives a Clean Water Act permit covering releases into waterways, a process that could take two and a half years. EPA estimates that it will take a while.
A judge ruled last year that the Forest Service must obtain a permit, but fire retardant drops may continue in the meantime because they are necessary to protect life and property.
During the lawsuit, Stahl said hundreds of pages of documents, including what purported to be an EPA list of contaminated air tanker bases, were left anonymously on the doorstep of an FSEEE attorney in Missoula, Montena. An accompanying letter, said to have been written by a longtime Forest Service employee, describes the presence of heavy metals such as cadmium and chromium in Foscek as “one of the flame retardant industry’s worst-kept secrets.”
Stahl said the threat of heavy metals in flame retardants could pose new regulatory challenges for the EPA, which creates Clean Water Act permits for the Forest Service, and his group added based on its findings. It added that it is considering whether legal action is warranted.
“When you dump flame retardants, no matter where you dump them in the watershed, you’re adding potentially large amounts of toxic heavy metals,” he said.
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