Individual and Mixture Toxicity of Pharmaceuticals Naproxen, Carbamazepine, and Sulfamethoxazole to Australian Striped Marsh Frog Tadpoles (Limnodynastes peronii)

Nonsteroidal human pharmaceuticals are prevalent in domestic wastewater and may find their way into the environment at low concentrations. Since most pharmaceuticals are designed to be biologically active at low concentrations, there is a risk that these compounds may affect aquatic wildlife. Of particular concern is the occurrence of pharmaceutical mixtures, which may lead to increased adverse effects compared to individual compounds. Interactive effects were previously demonstrated for amphibians exposed to pesticide mixtures, but no such studies investigating responses of amphibians to pharmaceutical mixtures are apparently available. Results demonstrated increased toxicity (loss of tactile response) of striped marsh frog (Limnodynastes peronii) tadpoles exposed to a mixture of naproxen, carbamazepine, and sulfamethoxazole, compared to exposures to the individual compounds. Significant time x treatment interactions were observed for tadpole development following chronic exposures to 10 or 100 mu g/L of each compound and the mixture; however, responses were weak and main treatment effects were not significant. Despite minor effects at low exposure concentrations, results demonstrated a potential for mixtures of nonsteroidal pharmaceuticals commonly occurring in wastewater to influence amphibian development. With the vast numbers of pharmaceuticals that exist and are found in the environment, this work highlights a need for further research into mixtures of pharmaceutically active wastewater contaminants. Further, since pharmaceuticals exert extremely varied biological actions, it is suggested that future investigations would benefit from inclusion of endpoints that are indicative of physiological or metabolic performance, as well as assessment of sensitive behavioral responses.