The main purpose of pink dye is simply to help firefighters and pilots accurately create and identify retardant lines.
“Essentially, it allows pilots to see where the lines are being dropped,” Horn said. “If it was clear, they wouldn’t know where the delay lines were.”
Phos-Chek can fade over time in the sun and be washed off with water, so it will not permanently stain a landscape.
Neptune Aviation, a The Montana-based airline is among the services currently providing fire retardants to fire-affected areas. The company contracts with the United States Forest Service and the California Department of Forestry and Fire Protection (Cal Fire).
Nic Lynn, vice president of operations for Neptune Aviation, said three of the company’s air tankers are used in Southern California. The planes use air bases designated and established by the government, he explained.
“We go to these pre-established refueling bases, where they mix the retardant and pump it into the planes. Think of us like we’re a dump truck. We will transport the product from A to B,” he said.
Neptune Aviation has flown at least 93 missions and delivered more than 280,000 gallons of retardant to fight fires, Lynn added.
To protect ecosystems, the Forest Service and Department of the Interior require aircraft to avoid dropping fire retardants within 300 feet of waterways (land deliveries must also avoid waterways). However, certain exceptions can be made, particularly if “the potential damage to natural resources exceeds the possible loss of aquatic life,” according to the Forest Service.
The main environmental concern associated with the retarder is the presence of heavy metals. A study last year suggested that one version of Phos-Chek contained higher levels of metals like cadmium and chromium than those considered safe under regulatory thresholds. Heavy metals are not added directly to the product but can come from natural impurities.
Horn, however, said the version of Phos-Chek launched in California is “a different product than years ago.”
Yifang Zhu, a professor of environmental health sciences at the Fielding School of Public Health at the University of California, Los Angeles, said the benefits of using flame retardants outweigh the risks.
“There is very little evidence that this causes serious long-term health effects” on people, Zhu said.
She added that the immediate health risks posed by wildfire smoke, which contains high levels of particulate matter, are more serious than potential concerns from fire retardant.
Exposure to smoke can cause a range of respiratory and cardiovascular problems, such as difficulty breathing, bronchitis or heart attacks, according to the Environmental Protection Agency.
