Quantitative structure‐activity relationships for the acute toxicity of chlorobenzenes to Daphnia magna

The relationships between physical‐chemical properties of aqueous solubility, octanol/water partition coefficient, vapor pressure, boiling and melting points and Henry's Law constant are discussed and illustrated for the chlorobenzenes. It is suggested that a critical review of such data is an essential component of quantitative structure‐activity relationship (QSAR) development and can elucidate the potential for air/water and organism/water partitioning during bioas‐says. Experimental 48‐h EC50 data are reported for Daphnia magna in a closed system and relationships established between EC50, solubility and octanol/water partition coefficient. It is suggested that when presenting QSAR data, logarithmic plots should be prepared of the toxic concentration versus both solubility and octanol/water partition coefficient. The results indicate that in this case the toxic effect is nonspecific in nature and that the EC50 is controlled primarily by organism/water partitioning.