What is the pink extinguishing powder that Los Angeles fire crews drop, and how does it work?

Some of the images that have come out of Los Angeles County over the past week are those we expect with wildfires: dramatic flames, orange skies and damaged structures.

But what is the story of the pink powder covering some neighborhoods?

The material covering streets, cars and roofs is actually fire retardant, and is dropped by aerial firefighting tankers in huge columns of red or pink.

Unlike water droplets, which target active fires, fire retardants are dropped by aircraft ahead of the fire’s path to slow the fire’s progress and allow crews to build fire lines.

Officials say thousands of gallons of fire retardant have been dropped in Los Angeles County since the fires broke out last week. The deadly fires have killed at least 25 people, destroyed more than 12,000 buildings and displaced tens of thousands of residents so far.

What exactly is flame retardant?

Fire retardants consist of chemical fertilizers such as ammonium phosphate. They often include bright pigments to help pilots drop the butt accurately.

They slow the rate of fires by cooling and coating the plants that serve as fuel for the fire, depleting the oxygen in the fire, and slowing the combustion process “as inorganic retardant salts change how the fuel burns,” according to the U.S. Forest Service.

Phos-Chek, manufactured 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 from The Associated Press.

Although there are many formulations, it generally comes in the form of a concentrated powder that is mixed with water before being dropped from conveyors.

Is it safe?

In general, fire retardants approved for use are not toxic to humans — although direct inhalation, eye contact or consumption can cause irritation, and scientists say more studies on long-term exposure are needed.

But fire retardants can be toxic to fish or other aquatic animals if they get into waterways. For this reason, the U.S. Forest Service prohibits dropping fire retardant within 300 feet of waterways or areas specifically designated to avoid fires, “except when human life or public safety is threatened.”

study Released last year The journal Environmental Science and Technology Letters found that some fire retardants, including Phos-Chek LC-95W, contain toxic metals, including lead and arsenic.

Representative of the US Forest Service He told NPR LC-95 will be phased out in 2025 in favor of the newer MVP-Fx formulation. According to ocean data, Phos-Chek MVP-Fx is Much less toxic For fishing older LC-95 fixtures.

Ocean has previously stated that residents should try to clean the dampers with mild soap and water as soon as safety allows.

“The longer the backside dries, the more difficult it is to completely remove it,” the company stated in its brief. Pressure washers can be used on larger surfaces, she added.

The bright color will slowly fade with exposure to sunlight.

Forest fires are linked to a range of health problems, with studies showing that long-term smoke inhalation can seriously affect the lungs, heart, and even Increases the risk of dementia More than other forms of air pollution.

The U.S. Forest Service has been using aerial fire retardants since the 1950s, according to its website, but their use has gone through several transformations over the years as older formulations have been phased out and regulations have changed.

In 2005, the U.S. District Court for the District of Montana ruled that the Forest Service violated the National Environmental Policy Act by failing to adequately analyze the impact of atmospheric fire retardants on the environment and endangered animals. After years of back and forth, the U.S. Forest Service conducted assessments and implemented a no-dumping requirement in waterways and avoidance areas in a 2011 decision.

Last year, the U.S. Forest Service announced it had decided not to enter into a contract with Compass Minerals for magnesium chloride-based aerial fire retardants after inspections found corrosion in the aerial conveyors used to spread the company’s retardants.