Defining the toxic mode of action of ester sulphonates using the joint toxicity of mixtures

Previously we have presented aquatic toxicity data for the class of anionic surfactant ester sulphonates (ES) to Daphnia magna. We now present toxicity data for binary mixtures of ES substances with reference substances of known mode of action. Using a toxic unit (TU) approach, data indicated that ES substances exhibit concentration addition with linear alkylbenzene sulphonate (LAS) and phenols and response addition with alcohols. This suggests that ES behave with a similar mode of action to phenol and LAS which are known polar narcotics and with a dissimilar mode of action to alcohols which are known baseline narcotics.