Prediction of the joint toxicity of five organophosphorus pesticides to Daphnia magna.

The individual toxicities of five organophosphorus pesticides (dichlorvos, parathion, methyl parathion, malathion and dimethoate) to Daphnia magna were investigated in 24-h immobilization experiments. Using these toxicity data, their combined toxicities were measured in pesticide mixtures designed using either 'equivalent-effect concentration ratios' or 'uniform-design concentration ratios'. The toxicities of mixtures of similarly or dissimilarly acting toxicants are often predicted from the individual toxicities of the component compounds, using one of two distinct biometric models: concentration addition (CA) or independent action (IA).