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In this Tuesday photo provided by the Colorado National Guard, an aircraft drops a load of fire retardant slurry above the High Park wildfire about 15 miles west of Fort Collins, Colo. The ammonium phosphate dropped from airplanes to slow the spread of raging wildfires can turn a pristine mountain stream into a death zone for trout and some say the retardant has never been proven effective.

Debate over fire retardant toxicity rages

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­CHEYENNE, Wyo. (AP) -- Add another concern for the tanker plane pilots who barnstorm low over treacherous terrain, in vintage aircraft, to bomb fire retardant around raging mountain wildfires: Endangered species.

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New U.S. Forest Service rules for the use of fire retardant in dozens of national forests seek to prevent the millions of gallons of fire retardant spread over the landscape every year from poisoning streams and killing off protected plants and fish.

Forest Service officials insist the new rules won't hinder firefighting. The company that operates almost half of the U.S. private fleet of large tanker planes agrees, for the most part.

"It is an increasing workload, there's no doubt about that," said Dan Snyder, president of Missoula, Mont.-based Neptune Aviation Services, which operates eight Lockheed P2V planes.

"It may reduce the speed at which they can affect the fire because they do need to take those few extra minutes to study the charts and plan on how they can put the retardant on the ground and still comply with the rules."

The group that brought about the changes by filing suit says the rules aren't as big of an issue as whether fire retardant even works.

The Forest Service has never proven in the field that fire retardant is effective, said Andy Stahl, executive director of Forest Service Employees for Environmental Ethics in Eugene, Ore.

"Why use it if it's not effective? If it's not effective, I don't care if it's environmentally benign. It's a waste of money and firefighters' lives," Stahl said.

"The case for retardant use is not sufficiently strong to offset the environmental effects."

Rubbish, say Forest Service officials, who cite decades of rigorous laboratory testing and relate the accounts of plenty of ground and aerial firefighters who insist that fire retardant not only works, it works well.

"When enough people in enough places say retardant helps, we have to believe they're not making it up," said Cecilia Johnson, fire chemicals technical specialist at the agency's Missoula Technology and Development Center in Montana.

The lab assesses not just the efficacy but the toxicity of fire retardant, which is blended into water and dumped from airplanes onto fire as a slurry mixture.

"All of the retardants as concentrates are practically nontoxic. They're even less toxic by the time they're diluted," Johnson said.

So who's right? The finer points of the debate get complicated.

Fire retardant doesn't attempt to put out wildfires or even necessarily halt flames in their advance. Consisting primarily of ammonium phosphate -- fertilizer, basically -- fire retardant is formulated to slow down the combustion of trees, brush and grass.

The idea is to give firefighters time to mount a ground attack. The ground forces clear away flammable material in a wide line around the edges of the fire. They hem in the flames and eventually a soaking rain falls or the fire just burns itself out.

Often, even a fully contained high Rockies wildfire will smolder, sputter and flare for weeks or months, into autumn and the first significant snows.

The U.S. Forest Service spent $19 million on 23 million gallons of retardant last year, which was unusually busy for wildfires.

Documented cases of fish killed by fire retardant are relatively rare. But they've happened.

"We've observed streams for miles be sterilized of all their fish life. Tens of thousands of fish can be killed in one dump," Stahl said.

In 2002, a slurry bomber inadvertently dumped between 1,000 and 2,000 gallons of fire retardant on the Fall River about 25 miles south of Bend, Ore.

The retardant immediately killed all of the river's fish, an estimated 21,000 mainly juvenile brown trout, redband trout and mountain whitefish over a six-mile stretch.

The fish population began to recover after a couple years, said Steve Marks, a fish biologist for the Oregon Department of Fish and Wildlife.

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