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Planes battling fires raging in the Los Angeles area are dropping more than just water: hundreds of thousands of gallons of bright pink fire extinguisher in front of the flames in a desperate effort to stop them before they destroy more neighborhoods.
The fires have killed at least 24 people, displaced thousands and destroyed more than 12,000 structures since they started last Tuesday. Four fires sparked by strong Santa Ana winds have charred about 100 square miles, according to Cal Fire.
Firefighting agencies say extinguishing products – most often used to fight wildfires – are an invaluable tool. But what’s in them and are they safe?
Here’s what you need to know:
The fires are burning quickly in canyons and other rugged areas that are difficult for ground firefighters to reach, Cal Fire said.
Although fire extinguishers can be very effective, they have their limitations, the agency said: Strong winds can make the low-altitude flight needed for drops too dangerous and can dissipate the retardant before it reaches the ground.
Besides Cal Fire, several agencies have abandoned fire retardants and water, including the U.S. Forest Service, the Los Angeles and Ventura County fire departments, the city and the National Guard.
Overhead fire extinguishers are typically a mixture of water, ammonium phosphate — essentially a fertilizer — and iron oxide, which is added to make the retardant visible, said Daniel McCurry, a professor of civil and environmental engineering at the University of Southern California.
The Forest Service, which used 13 planes to drop extinguishing agents on the Los Angeles fires, says they helped deprive a fire of oxygen and slow the rate of burning by cooling and covering vegetation and d other surfaces.
Perimeter, the company that supplies fire retardants to the Forest Service and other agencies, says phosphate changes the way the cellulose in plants breaks down and makes them nonflammable.
Potential effects on the environment and wildlife
Fire extinguishing products are generally considered safe for humans, but many are concerned about their potential effects on wildlife.
The Forest Service prohibits the use of aerial control products on waterways and endangered species habitats, “except when human life or public safety is threatened,” due to potential effects on fish health and other wild animals.
USC’s McCurry said he and other researchers tested several inhibitors and found heavy metals, including chromium and cadmium, in a product commonly used by the U.S. Forest Service.
McCurry said the study results suggest it’s “plausible” that fire extinguishers could contribute to spikes in chromium and other heavy metals in waterways downstream of wildfires.
“We don’t yet have definitive proof because it is difficult, but not impossible, to prove the origin of a heavy metal,” McCurry said. “We’re working on it.”
Perimeter, the manufacturer of the Forest Service’s fire retardant, said McCurry’s research focused on a formulation that was not used in California and is no longer used by the Forest Service. The company also claims that it does not add metals, which it says are naturally present in all ammonium phosphate fertilizers, and that its lampshades “are comprehensively tested by the Forest Service. USDA and meet or exceed all health and safety standards.
The use of fire retardants is imperative to extinguish wildfires that expose millions of people to health risks, including from a toxic mix of microscopic particles that can cause respiratory and heart problems by penetrating deep into the lungs and blood circulation.
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Studies have shown that smoke from wildfires accounted for up to half of all health-harming particulate air pollution in the western United States in recent years, with warming temperatures fueling more destructive fires .
And a study published last year by the Alzheimer’s Association found that wildfire smoke may be worse for brain health than other types of air pollution, increasing the risk of dementia.
“Using forest fire retardants is the best way to save lives, protect communities and limit fires,” said Edward Goldberg, vice president of solutions at Perimeter Institute.
McCurry, the USC researcher, said more study is needed on extinguishing products — including in Los Angeles after the fires are extinguished — but he understands their value: “If there was a brush fire that was approaching my house, I would still rather than paint. lots of (fireproof) in front.