Synopsis of the international workshop advances in environmental hazard and risk assessment September 21 – 23, 1987, Schmallenberg-Grafschaft

Abstract

The effect of hydrophobic organic chemicals on the rate of feeding by mussels (Mytilus edulis) was investigated. The effect was expressed as the toxicant concentration in water required to reduce feeding rate by 50% (WEC50). A quantitative structure-activity relationship (QSAR) was derived in which WEC50 was negatively correlated with log10 octanol-water partition coefficient (log Kow) and positively correlated with aqueous solubility, indicating that hydrophobicity has a major influence on toxicity. QSARs calculated between bioconcentration factor, and log Kow and aqueous solubility showed, that hydrophobicity influences toxicity largely through its effect on bioconcentration. This observation was confirmed by expressing toxicity as the toxicant concentration in mussel tissue required to reduce feeding rate by 50% (TEC50). For the compounds tested which have log Kow values< 4.6, TEC50 was relatively constant, irrespective of molecular structure.Compounds with log Kow values > 5 could be accumulated to much greater concentrations before feeding rate was affected, indicating that there is a ‘molecular weight cut-off’ in the toxicological response.These observations are characteristic of a non-specific narcotic mode of toxic action. The application of the reported QSARs to interpreting results derived from combined chemical contamination and biological effects environmental monitoring studies with mussels is discussed.