Acute aquatic toxicity of alkyl phenol ethoxylates.

The recently derived log Kow (octanol/water partition coefficient in logarithmic form) increment for a nonterminal oxyethylene unit was used to calculate a quantitative structure-activity relationships for literature data on the acute crustacean toxicity of polyoxyethylene surfactants. The resulting log Kow regression parameters are between the corresponding values for nonpolar and polar narcosis, which supports an interpretation of the surfactants' aquatic toxicity on the basis of another distinct mode of action. Furthermore, a comparison with calculated water solubility data indicates that for log Kow greater than 5 an aquatic toxicity decrease due to a solubility limit is expected, which gets support from two other sets on toxicity data of nonyl phenol polyethoxylates.