Altered Metabolic Elimination of Testosterone and Associated Toxicity Following Exposure ofDaphnia magnato Nonylphenol Polyethoxylate

The ability of nonylphenol polyethoxylate (nonylphenyl polyethylene glycol, NPPG) to alter the metabolic elimination of testosterone and elicit reproductive toxicity toDaphnia magnawas assessed. NPPG (5.0 mg/liter) inhibited the elimination of testosterone as glucose and sulfate conjugates, but had minimal effect on the rate of elimination of oxido-reduced and hydroxylated derivatives of the steroid hormone. This exposure concentration of NPPG also approximated the acute threshold-effect concentration and the chronic value for daphnids. Results demonstrated that NPPG qualitatively elicits similar effects on the metabolic elimination of testosterone by daphnids as previously characterized with its degradation product 4-nonylphenol. Unlike 4-nonylphenol, significant chronic toxicity of NPPG, due to effects on steroid elimination processes, was not evident. Results from the present study provide no indication that concentrations of nonylphenol polyethoxylates typically measured in the environment pose a risk of chronic toxicity to invertebrates.