Is the Pink Substance Dropped on LA Fires Safe?

The efforts to battle widespread fires across Los Angeles included aircraft drops of a bright red and pink substance.

The material covered forests, homes, cars, and other things in the path of the wind-fueled fires. Because the substance was dropped in many residential areas, some people have wondered how safe it is.

The material is a fire retardant. The kind dropped around Los Angeles was mostly a product called Phos-Chek. The substance has been used by the U.S. Forest Service to fight fires since the 1960s.

Jason Colquhoun is a 53-year-old pilot with HeliQwest, an aircraft company specializing in firefighting activities. He told the French news agency Agence France-Presse (AFP) that using the Barbie-pink material makes his job easier. "You can see it so easily ... it's amazing," he said.

Daniel McCurry is an associate professor of civil and environmental engineering at the University of Southern California. He said that in recent weeks, Phos-Chek had been dropped in residential areas more than ever before. That fact has led many to question its safety.

Phos-Chek is sold by fire protection equipment supplier Perimeter Solutions. It is a mixture of mostly ammonium phosphate or ammonium polyphosphate. These substances are also used to produce fertilizer. Other chemicals are added to the mixture to give it color. Perimeter told AFP the substance is designed to be one color. But it can look different depending on time of day, lighting, or smoke.

The bright pink color helps pilots as they try to make sure they have covered a whole area, Colquhoun explained. He noted that when pilots drop water from the air, they have to search for "the shine and the darkness" to know where to make the next drop. The colorful retardant, however, is "so much easier to spot," Colquhoun said.

McCurry said another reason it is better than water is that it keeps working even after the water it is mixed with dries. Phos-Chek is made thick so the wind does not blow it away and to ensure that it covers the desired area.

McCurry explained the substance works by forming a coating that will not burn. After the water dries up, the retardant keeps working until rain washes it into the ground. McCurry said a former firefighter told him that in a high-intensity fire the substance is "not much use." He added that the high winds driving the fires in Los Angeles may have limited its effectiveness.

U.S. Forest Service spokesperson Wade Muehlhof said the agency only uses retardants that meet U.S. government rules for not being harmful to animals, humans, or things living in water. He told AFP the Forest Service usually does not drop the retardant in waterways and areas home to endangered animals -- unless the fire is threatening human life or public safety. But accidents do happen, he said, and the wind may blow it into such areas.

McCurry said he believes Phos-Chek is “likely not harmless to the environment” now. But, he added, "On the other hand, the human health impact is still a little unclear." He noted that it would take "a lot" of retardant to poison, say, a large body of water.

But he said that as firefighters battled the Los Angeles fires, the substance was dropped on a lot of neighborhoods in “unprecedented” amounts. McCurry said Phos-Chek is more often used further from populated areas, or in lesser amounts. "So, who knows," he added.

I’m Jill Robbins.

Huw Griffith and Sarah Titterton reported this story for Agence France-Presse. Jill Robbins adapted it for Learning English.

residential – adj. an area where people live

retardant – n. something that is able to slow down the progress or development of something

amazing – adj. causing great surprise or wonder

coating – n. a thin layer of material that covers the surface of something

impact – n. a powerful or major influence or effect

unprecedented – adj. never having happened before

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