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Fire Effects
Rebecca Hodgeson
Physical Geology
Spring 2008


Fire Retardant Environmental Effects



See Work Cited for Photo Credits




Fire Retardant is a chemical that is used to help contain wildfires and prescribed burns. The retardant is dropped from an aircraft to construct a fire line. Often, these chemicals are dropped in environmentally sensitive area. These areas may include endangered or threatened species of plants and animals. The retardant or slurry is a mixture of chemicals, some of which are to prevent corrosion. The slurry is designed to prevent the vegetation from igniting. Many of the chemicals are designed to keep the slurry from separating before it hits the targeted areas. Iron oxides are added to make the retardant turn red so aircraft pilots can see their previous drops. Agricultural fertilizers such as Ammonium Phosphate and Ammonium Sulfate are also added to help plant growth after the burn. (Larson)


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Retardant Effects

            Fire retardants are a useful firefighting tool; unfortunately the chemicals that suppress these blazes come with a price on the environment. Nitrogen found in Ammonium Phosphate and Ammonium Sulfate are damaging to aquatic ecosystems. The Nitrogen creates algae blooms that can suffocate fish. The U.S. Geological Survey’s Northern Prairie Wildlife Research Center reported in 1998 that long-term retardants are, “very toxic to aquatic organisms including algae, aquatic invertebrates and fish.” The survey also said retardants, “could cause substantial fish kills depending on the stream size and flow rate.” Other studies reported that natural species could not adapt to the excess nitrogen as well as other weedier species. The retardant chemicals also slowed down the reproductive process in the natural species making them unable or less likely to compete.  These Factors over all reduced the amount of diversity within the plants in the area. (Effects of Fire Retardant Chemicals on Environment)



Guard, Reserve aid in California firefighting efforts

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According to Earth Talk by the editors of E/ Enviromental Magazine, “In recent years, where global warming and draughts have often exacerbated forest fires the American West, federal and state firefighting agencies have upped their cumulative annual use of long-term retardants to some 20+ million gallons a year spread across tens of thousands of individual fly-overs.”



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            Aerial firefighting regulations were released in 2000 by the United States Forest Service for the use of fire retardant. The purpose of the guidelines was mostly for the safety of pilots, ground crews, and fire control. The documents encouraged pilots to avoid making drops in sensitive areas and within three hundred feet of streams, lakes, and other water sources. The retardant is used to help control large and fast moving fires as well as prevent sending ground crews into risky situations. (Effects of Fire Retardant Chemicals on Environment)



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Retardant Effects on Rainbow Trout

            A U.S. Geological Survey was conducted by the Columbia Environmental Research Center to determine the effects of three ammonia based fire retardants and five suppressant foams on juvenile Rainbow Trout. The three retardants were listed as Fire-Trol LCA-F, Fire-Trol LCM-R, and Phos-Chek 259F. The most toxic retardant was Phos-Chek 259F, followed by Fire-Trol LCA-F, and least toxic was Fire-Trol LCM-R. The results concluded that with the exception of one fire foam (Pyrocap-B-136) the retardants were less toxic than fire foams. The survey stated, “ Comparisons of recommended application concentrations to the test results indicate that accidental inputs of these chemicals into streams require substantial dilutions to reach concentrations non-lethal to Rainbow Trout. (Buhl)


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Fire Retardant Effects on Chinook Salmon

            A U.S. Geological Survey was conducted by the Enviromental and Contaminants Research Center to determine the toxic levels of three fire retardants and two fire foams to early stages of Chinook Salomon in both hard and soft water. The fire retardants were listed as Fire-Trol GTS-R, Fire-Trol LCG-R, and Phos-Chek D75-F. Fire suppressant foams; Phos-Chek WD-881 and Ansul Silv-EX. The study found that the fire retardants were less toxic than fire foams in both hard and soft water. They were also less toxic in all life stages. The survey found that water type had minor effects on the levels of chemical toxicity. The chemicals range from most to least toxic starting with Phos-Chek-WD-881(Foam), Ansul Silv-EX (Foam), Phos-Chek D75-F, Fire-Trol GTS-R, and Fire-Trol LCG-R. The survey concluded that these chemicals would require “substantial dilution” if accidentally added to streams. (Buhl)


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Work Cited


Buhl, Kevin J.. "Acute Toxicity of Fire-Control Chemicals, Nitrrogenous Chemicals." , and Trout. 28/04/1999. AmericanFisherySociety. 04 Apr 2008 abstract&issn=1548-8659&volume=129&issue=2&page=408&ct=1

Buhl, Kevin J.. "Acute Toxicity of Fire-Rretardant and Foam Suppressant Chemiclas to Early Life Stages of Chinook Salmon." Enviromental ZToxicology and Chemistry. 28/04/1999. American Fishery Society. 24 Apr 2008 abstract&issn=1548-8659&volume=129&issue=2&page=408&ct=1

"Effects of Fire Retardant Chemicals on Enviroment." 31/03/2008. The Enviromental Magizine. 01Apr 2008

Larson, Diane L., Westly E. Newton, Patrick J. Anderson, and Steven J. Stein. "Effects of Fire Chemical and Fire Suppressant Foam on Shrub Steppe Vegetation in Northern Nevada." International Journal of Wildland Fire. (1999): 115-127.


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