The acute toxicity of selected substituted phenols, benzenes and benzoic acid esters to fathead minnows Pimephales promelas

Flow-through acute toxicity tests were conducted with 24 organic compounds using fathead minnows Pimephales promelas as test organisms. The tested toxicants consisted of 11 substituted phenols, four substituted benzenes and nine esters. The 96-h LC 50 values determined for these compounds when tested against fathead minnows ranged from 0·135 mg litre −1 for nonylphenol to 117 mg litre −1 for nitrobenzene. Adverse sublethal effects were observed in fathead minnows at exposure concentrations below the 96-h LC 50 value with 14 of the 24 compounds tested. Acute toxicity tests were also conducted with 2,3,4,5-tetrachlorophenol using rainbow trout Salmo gairdneri ; with 1,4-dinitrobenzene, 2-ethoxyethylacetate, ethyl salicylate and phenyl salicylate using both channel catfish Ictalurus punctatus and snails Aplexa hypnorum ; and with 4-nitrophenol using channel catfish. The 96-h LC 50 for rainbow trout when tested against 2,3,4,5-tetrachlorophenol was 0·205 mg litre −1 , while 96-h LC 50 values for channel catfish ranged from 0·673 to 44·8 mg litre −1 with 1,4-dinitrobenzene and 2-ethoxyethylacetate, respectively. Snail 96-h LC 50 values ranged from 4·24 mg litre −1 for 1,4-dinitrobenzene to 65·2 mg litre −1 for 2-ethoxyethylacetate.