Differential toxicities of anionic and nonionic surfactants in fish.

This study investigated the differential toxicities of anionic and nonionic surfactants commonly used as active ingredients in household cleaning agents. The acute toxicity of the surfactants against Clarias gariepinus were investigated using static bioassays while the sublethal effects on the biochemical parameters and the histopathology of liver and gills of the fish were investigated for a period of 28 days using a static renewal bioassay. The anionic surfactants were found to be more acutely toxic against the fish than the nonionic surfactants. The evaluation of the joint action toxicity of the surfactants against the test species using the concentration-addition model showed antagonistic interactions when the surfactants are present in mixtures. The two groups of surfactants also had varying degree of effects on the antioxidant stress enzymes and the liver function enzymes of the fish. However, only the anionic surfactants caused changes in the histopathology of the gills of the fish. The results obtained from this study have shown that anionic surfactants are more toxic to fish compared to nonionic surfactants. Anionic surfactants are the most commonly used surfactants in cleaning agents, there is a need for stricter regulations governing the use of this class of surfactants in cleaning agents.