Joint-action ecotoxicity of binary mixtures of glutaraldehyde and surfactants used in hospitals: Use of the Toxicity Index model and isoblogram representation

Glutaraldehyde and surfactants are widely used in hospitals and these substances have been detected in urban sewer networks and in surface water. The ecotoxicity of hospital wastewater has been reported in the literature, which identifies detergents and disinfectants as the main causes of toxicity. The aim of this study was to determine the combined effects of glutaraldehyde and three surfactants on Daphnia magna. Three binary mixtures were studied in five predefined ratios: glutaraldehyde with sodium dodecyl sulfate (SDS—an anionic surfactant), then Triton X-100 (TX-100—a nonionic surfactant), and finally cetyltrimethyl ammonium bromide (CATB—a cationic surfactant). The joint-action toxicity of binary mixtures was studied by acute bioassays on Daphnia magna. Two complementary methods were used to evaluate the combined effects of the mixtures on the selected organism: the Toxicity Index model (a quantitative method for analyzing the combined effects of binary and multiple mixtures) and the isobole representation (a qualitative method that has the advantage of being illustrative). An additive effect was observed between glutaraldehyde and surfactants for all the ratios studied and additive action could be an efficient method for evaluating the effect of hospital wastewater on Daphnia magna.