QSAR Modeling of Acute Aquatic Toxicity of Ethoxylated Alcohol Mixtures, and Estimation of Solubility Cut-Offs

Commercial nonionic surfactants are multicomponent mixtures, typically derived from ethoxylation of a primary alcohol that may be a mixture of homologues and isomers with a range of degrees of ethoxylation. Daphnia magna and Vibrio fischeri toxicity data have been obtained for several nonionic surfactants, covering a wide range of average degrees of ethoxylation and parent alcohol structure, including both narrow-range and broad-range ethoxamer distributions. These data are analyzed by means of a general narcosis quantitative structure–activity relationship (QSAR) based on calculated log P values together with mixture toxicity equations. In some cases not all components are sufficiently soluble to make their full toxic contributions. An approach for identifying such components and for taking their reduced toxic contributions into account is derived from previously published structure-solubility relationships and validated against the experimental toxicity data.