Acute toxicity of fire-control chemicals, nitrogenous chemicals, and surfactants to rainbow trout

Laboratory studies were conducted to determine the acute toxicity of three ammonia based fire retardants (Fire-Trol LCA-E Fire-Trol LCM-R, and Phos-Ch ek 259F), five surfactant-based fire-suppressant foams (FireFoam 103B, Fire Foam 104, Fire Quench, ForExpan S, and Pyrocap B-136), three nitrogenous ch emicals (ammonia. nitrate, and nitrite), and two anionic surfactants (linea r alkylbenzene sulfonate [LAS] and sodium dodecyl sulfate [SDS]) to juvenil e rainbow trout Oncorhynchus mykiss in soft water. The descending rank orde r of toxicity (96-h concentration lethal to 50% of test organisms [96-h LC5 0]) for the fire retardants was as follows: Phos-Chek 259F (168 mg/L) > Fir e-Trol LCA-F (942 mg/L) = Fire-Trol LCM-R (1,141 mg/L). The descending rank order of toxicity for the foams was as follows: FireFoam 103B (12.2 mg/L) = FireFoam 104 (13.0 mg/L) > ForExpan S (21.8 mg/L) > Fire Quench (39.0 mg/ L)> Pyrocap B-136 (156 mg/L). Except for Pyrocap B-136, the foams were more toxic than the fire retardants. Un-ionized ammonia (NH3; 0.125 mg/L as N) was about six times more toxic than nitrite (0.79 mg/L NO2-N) and about 13, 300 times more toxic than nitrate (1,658 mg/L NO3-N). Linear alkylbenzene s ulfonate (5.0 mg/L) was about five times more toxic than SDS (24.9 mg/L). E stimated total ammonia and NH, concentrations at the 96-h LC50s of the fire retardants indicated that ammonia was the primary toxic component in these formulations. Based on estimated anionic surfactant concentrations at the 96-h LC50s of the foams and reference surfactants, LAS was intermediate in toxicity and SDS was less toxic to rainbow trout when compared with the foa ms. Comparisons of recommended application concentrations to the test resul ts indicate that accidental inputs of these chemicals into streams require substantial dilutions (100-1,750-fold) to reach concentrations nonlethal to rainbow trout.