Parts of Southern California have become enveloped in a striking pink hue as firefighters continue their battle against the raging wildfires in Los Angeles. This vivid coloration stems from the use of Phos-Chek fire retardant, a key tool in the firefighting arsenal. Manufactured by Perimeter Solutions, Phos-Chek is a powder concentrate mixed with water to form a foam or slurry. The mixture is then deployed over affected areas to combat the fires. But what exactly is Phos-Chek, and is it safe for the environment and communities?
The principal component of Phos-Chek MVP-Fx is monoammonium phosphate, which constitutes 80% to 90% of the formula. This ingredient is complemented by diammonium phosphate and various performance additives, as detailed in the MVP-Fx safety data sheet. The retardant's bright pink color serves a vital purpose, enabling pilots and firefighters to identify treated areas from both the air and the ground.
Perimeter Solutions has designed the Phos-Chek mixture to work by depriving fires of fuel, thus diminishing their intensity and slowing their spread. The inorganic salts present in the formula alter how the fuels burn. According to Forest Service guidelines, the retardant effectively depletes oxygen around the fire, reducing combustion rates. The formulation contains fertilizers and other components that persist even after the water evaporates, providing ongoing protection by delaying fire spread for days or even weeks.
However, concerns about environmental impact have been raised. A 2024 study published in Environmental Science and Technology Letters highlighted that long-term fire retardants contain toxic metals such as lead, arsenic, and thallium. Perimeter Solutions acknowledges on its safety data sheet that Phos-Chek "may cause long-term adverse effects in the aquatic environment."
"may cause long-term adverse effects in the aquatic environment." – Perimeter Solutions
Despite these concerns, a spokesperson for Perimeter Solutions assured The New York Times that their products used in aerial firefighting have undergone "extensive testing to confirm they meet strict standards for aquatic and mammalian safety." The U.S. Forest Service has adopted Phos-Chek MVP-Fx nationwide, phasing out the older Phos-Chek LC95W product. Available data indicates that MVP-Fx presents less toxicity to aquatic life than its predecessor.
In terms of human safety, Perimeter Solutions describes the product as "minimally irritating to the eyes" and "non-irritating to skin."
"minimally irritating to the eyes" and "non-irritating to skin" – Perimeter Solutions
The use of Phos-Chek aligns with Forest Service guidelines, which permit its deployment under specific circumstances. These include situations where human lives or public safety are at risk, and when the retardant's application could significantly reduce the threat posed by a fire.
"when human life or public safety are threatened and retardant use in the aerial retardant avoidance area could be reasonably expected to alleviate the fire threat," – Forest Service guidelines
The Phos-Chek MVP-Fx formulation's effectiveness lies in its ability to alter how fires consume fuel. By creating a barrier between the flames and potential fuel sources, it minimizes fire intensity and curtails its spread rapidly.
"This deprives the fire of fuel, reducing fire intensity and rate of spread," – Perimeter Solutions
As sunlight gradually fades the bright pink color of the retardant, its usefulness remains evident in the continued effort to tame nature's fury. The vibrant hue may be temporary, but its role in safeguarding lives and property is enduring.
