What do pink dust fire crews drop in LA and how does it work?
Some of the images coming out of Los Angeles County last week are what we’ve come to expect from wildfires: dramatic flames, orange skies and damaged structures.
And what’s with the pink dust covering some neighborhoods?
The conspicuous substance that covers streets, cars and surfaces is actually fire retardant, dropped by fire tankers from the air in massive plumes of red or pink.
Unlike water drops that target an active flame, fire retardant is dropped by aircraft ahead of a fire to slow the fire’s progress and allow crews to lay down fire lines.
Thousands of gallons of fire retardant were dumped in Los Angeles County after last week’s fires, officials said. The deadly fires have so far killed at least 25 people, destroyed more than 12,000 structures and displaced tens of thousands of residents.
What exactly is fire retardant?
Fire retardants consist of fertilizer chemicals such as ammonium phosphates. Often includes bright pigments to help pilots accurately throw the retarder.
According to the US Forest Service, they try to slow fires by cooling and covering the plants that fuel the fire, depleting the fire’s oxygen and slowing the burning process because “the inorganic salts of the retardant alter the way the fuel burns.”
Phos-Chek, made by Perimeter Solutions, is the retardant used in Los Angeles County and the most widely used in Canada. It is also the most widely used fire retardant in the world, according to a 2022 report by The Associated Press.
Although it comes in several forms, it generally comes in a powder concentrate that is mixed with water before being discharged from tankers.
Is it safe?
In general, fire retardants approved for use are not considered toxic to humans — although direct inhalation, eye contact or consumption can cause irritation, and scientists say more research is needed on long-term exposure.
But fire retardants can be toxic to fish or other aquatic life if they get into waterways. For this reason, the US Forest Service prohibits the dumping of fire retardant within 300 feet of waterways or in designated avoidance areas “except when human life or public safety is threatened.”
A study released last year in the journal Environmental Science & Technology Letters found that some fire retardants, including Phos-Chek LC-95W, contained toxic metals including lead and arsenic.
A representative of the US Forest Service told NPR It said LC-95 was being phased out in 2025 in favor of the newer MVP-Fx formulation. According to perimeter data, Phos-Chek MVP-Fx less toxic catching more fish than the older LC-95 formulations.
Perimeter previously said residents should try to clean the retardants with water and mild soap as soon as safety allows.
“The longer the retarder sets, the harder it is to remove it completely,” the company said in a brief. Pressure washers can be used on larger surfaces, he added.
The bright color will fade slowly when exposed to sunlight.
Wayne Coulson, CEO of Vancouver-based Coulson Aviation, says most of his flights to support fire crews in Los Angeles have been at night.
Forest fires are associated with a number of health problems, studies show that long-term smoke inhalation can seriously affect the lungs and heart, and even. increases the risk of dementia more than any other form of air pollution.
The U.S. Forest Service has been using airborne fire retardants since the 1950s, according to its website, but its use has undergone many changes over the years as older formulations have been phased out and regulations changed.
In 2005, the US District Court for the District of Montana ruled that the Forest Service violated the National Environmental Policy Act by failing to properly analyze the effects of aerial flame retardants on the environment and endangered species. After years of back-and-forth, the U.S. Forest Service conducted assessments and in a 2011 decision implemented a requirement not to discharge waste into waterways and avoidance zones.
Last year, the U.S. Forest Service announced it had decided to award a contract to Compass Minerals for magnesium chloride-based air fire retardants after inspections found corrosion in the air tankers used to store the company’s retardant.
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