In this study quantitative structure-activity relationships (QSARs) were calculated between hydrophobicity of a group of organic chemicals with anaesthetic potency and toxicity (immobilization, mortality and inhibition of reproduction) to Daphnia magna. Differences in slopes of the high quality QSARs might be explained in terms of possible different sites of action for the three criteria of effect.The combined effects of mixtures of 5-50 chemicals on immobilization and mortality did not deviate from additivity, while the effect on reproduction deviated somewhat from it.

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