Some of the images coming out of Los Angeles County this past week are the ones we’ve come to expect associated with wildfires: dramatic flames, orange skies and damaged buildings.
But what’s with the pink powder that covers some quarters?
The eye-catching substance that covers streets, cars and surfaces is actually fire retardant and is dropped from aerial fire trucks in huge red or pink plumes.
Unlike water drops, which target active flames, fire retardants are dropped from aircraft in advance of a fire’s path to slow the fire’s progression and allow crews to establish fire lines.
Thousands of gallons of fire retardant have been dropped in Los Angeles County since the fires broke out last week, officials said. The deadly fires have so far killed at least 25 people, destroyed more than 12,000 buildings and displaced tens of thousands of residents.
What exactly is fire retardant?
Flame retardants consist of fertilizers such as ammonium phosphates. They often contain bright pigments to help pilots drop the retardant accurately.
They work to slow the spread of fires by cooling and coating equipment that serves as fuel for a fire, which deprives the fire of oxygen and slows the combustion process “as the retardant’s inorganic salts change the way it works.” “How fuels burn,” according to the US Forest Service.
Phos-Chek, manufactured by Perimeter Solutions, is the inhibitor used in Los Angeles County and the most commonly used in Canada. It is also the most widely used flame retardant in the world, according to a 2022 report by The Associated Press.
Although there are several formulations, it is generally a powder concentrate that is mixed with water before being dropped from tankers.
Is it safe?
In general, flame retardants approved for use are not considered toxic to humans – but direct inhalation, eye contact or consumption can cause irritation and scientists say more studies on long-term exposure are needed.
But flame retardants can be toxic to fish and other aquatic animals if they enter waterways. For this reason, the U.S. Forest Service prohibits the dropping of fire retardants within 300 feet of waterways or specially designated restricted areas “except when life or public safety is at risk.”
A study published last year in the journal Environmental Science & Technology Letters found that some flame retardants, including Phos-Chek LC-95W, contained toxic metals, including lead and arsenic.
A representative of the US Forest Service said NPR that LC-95 will be phased out in 2025 in favor of the newer MVP-Fx formulation. According to Perimeter data, Phos-Chek is MVP-Fx much less toxic for fishing than the older LC-95 formulations.
Perimeter has previously stated that residents should attempt to remove the retardant with water and mild soap as soon as safety permits.
“The longer the retardant dries, the more difficult it is to completely remove it,” the company said in a statement. High-pressure cleaners could be used on larger areas, it said.
The bright color slowly fades when exposed to sunlight.
Wayne Coulson, CEO of Vancouver-based Coulson Aviation, says most of his company’s flights to support firefighters in Los Angeles have been operated at night.
Wildfires are associated with a number of health problems. Studies show that inhaling smoke for long periods of time can have severe effects on the lungs and heart, and even increases the risk of dementia more than other forms of air pollution.
According to their website, the U.S. Forest Service has been using aerial fire retardants since the 1950s, but its use has undergone many changes over the years as older formulations have been retired and regulations 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 conduct a proper analysis of the effects of aerial fire retardants on the environment and endangered wildlife. After years of back and forth, the U.S. Forest Service conducted assessments and, in a 2011 decision, implemented the requirement that no dumping be allowed on waterways and avoidance zones.
Last year, the U.S. Forest Service announced it had decided against entering into a contract with Compass Minerals for magnesium chloride-based airborne fire retardants after inspections found corrosion in the air tankers using the company’s fire retardants.
Pascal Duclos, the chief pilot of Quebec’s air service, says crews are growing tired after days of dousing wildfires in California in high winds over mountainous terrain.
