Aquatic toxicity evaluation of para-methylstyrene

Abstract The aquatic toxicity of para -methylstyrene was evaluated in acute toxicity studies using fathead minnows ( Pimephales promelas ), daphnids ( Daphnia magna ), and freshwater green algae ( Selenastrum capricornutum ). Static tests were performed in sealed containers with no headspace to minimize loss of this volatile compound to the atmosphere. Concentrations of para -methylstyrene in test solutions were analyzed by gas chromatography equipped with a purge and trap module and flame ionization detection. Test results are based on mean, measured concentrations. para -Methylstyrene was moderately toxic to fathead minnows, daphnids, and green algae. The 96-h LC 50 and NOEC for fathead minnows were 5.2 and 2.6 mg/L, respectively. The 48-h EC 50 and NOEC for daphnids were 1.3 and 0.81 mg/L, respectively. The 72-h EC 50 and NOEC for green algae were 2.3 and 0.53 mg/L, respectively; these effects were algistatic rather than algicidal. para -Methylstyrene's potential impact on aquatic ecosystems is significantly mitigated by its volatility, an important fate process.