Laboratory studies were conducted with live early life stages of rainbow trout, Oncorhynchus mykiss, to determine the acute toxicities of five fire-fighting chemical formulations in standardized soft and hard water. Eyed egg, embryo-larvae, swim-up fry, and 60- and 90-d posthatch juveniles were exposed to three fire retardants (Fire-Trol LCG-R, Fire-Trol GTS-R, and Phos-Chek D75-F) and two fire-suppressant foams (Phos-Chek WD-881 and Silv-Ex). Swim-up fry were generally the most sensitive life stage, whereas the eyed-egg was the least sensitive. Toxicity of fire-fighting formulations was greater in hard water than in soft water for all life stages tested with Fire-Trol GTS-R and Silv-Ex and for 90-d-old juveniles tested with Fire-Trol LCG-R. The fire-suppressant foams were more toxic than the fire retardants. The 96-h median lethal concentrations (LC50s) were ranked from the most toxic to the least toxic formulation as follows (ranges are the lowest and highest 96-h LC50 calculated for each formulation): Phos-Chek WD-881 (11-44 mg/L), Silv-Ex (11-78 mg/L), Phos-Chek D75-F (218->3,600 mg/L), Fire-Trol GTS-R (207->6,000 mg/L), and Fire-Trol LCG-R (872->10,000 mg/L). Toxicity values suggest that accidental entry of fire-fighting chemicals into aquatic environments could adversely affect fish populations.
