Ecological Effects of Fire Retardant Chemicals and Fire Suppressant Foams

Laboratory studies with algae, aquatic invertebrates, and fish. Short-term
toxicity tests showed that both fire-retardant and foam-suppressant chemicals
were very toxic to aquatic organisms including algae, aquatic invertebrates,
and fish. Foam-suppressant are more toxic than fire-retardant chemicals. The
primary toxicant in fire-retardants is the ammonia component, whereas the
nitrite and nitrate components do not seem to contribute much to the toxicity
of the formulations. In foam suppressants the primary toxicant is the
surfactant component. The most sensitive life-stage for fish is the swim-up
stage. Accidental spills of fire-fighting chemicals in streams could cause
substantial fish kills depending on the stream size and flow rate. For example,
the retardant Fire-Trol GTS-R is prepared for field use by mixing 1.66 pounds
per gallon of water to produce 1.1 gallons of slurry, which is equivalent to
198,930 mg/liter. Comparing the concentration of FT GTS-R field mixture to the
acute toxicity values for the most sensitive life stage for rainbow trout gives
a ratio of 853 in soft water and 1474 in hard water. Applying a safety factor
of 100 to this ratio suggests a dilution of 85, 300 in soft water and 147,400
in hard water is needed to lower the chemical concentration in a receiving
water to limit adverse effects, i.e., fish kill, in a stream. For rainbow
trout, other dilution factors would be 52,100 for Fire-Trol LCG-R, 85,600 for
Phos-Chek D75-F, 71,400 for Phos-Chek WD-881, and 50,000 for Silv-ex.
Fire-fighting chemicals are very toxic in aquatic environments and fire control
managers need to consider protection of aquatic resources, especially if
endangered species are present.