The thyroid endocrine disruptor perchlorate affects reproduction, growth, and survival of mosquitofish

The perchlorate anion - an oxidizer found in rockets, missiles, some ammunition, flares, airbags, and fireworks - occurs as a contaminant in ground and surface water in many parts of the United States. Its toxic effects include inhibition of thyroid hormone synthesis. To investigate its chronic toxicity, mosquitofish (Gambusia holbrooki) adults and fry were exposed to aqueous sodium perchlorate at 1, 10, and 100 mg/L, and growth and reproductive performance (fecundity, eggs/embryos mass, and gonadosomatic index [GSI]) were determined. Five-day acute toxicity tests were also performed. Perchlorate had a stimulatory effect on fecundity, GSI, and egg/embryo mass, at least for some treatments. The LC₅₀ of sodium perchlorate was 404 mg/L. Growth was enhanced at 1 mg/L but inhibited at 10 mg/L. These results suggest that, at environmentally relevant concentrations, perchlorate does not induce acutely toxic effects but may have mild stimulatory or hormetic effects on fitness parameters in this species.