Acute toxicity, accumulation and excretion of organophosphorous insecticides and their oxidation products in killifish

Acute toxicity, accumulation and excretion of four organophosphorous insecticides (diazinon, malathion, fenitrothion and EPN) and their oxidation products (diazinon oxon, malaoxon, fenitrothion oxon and EPN oxon) were studied for killifish (Oryzias latipes). The 48-hr LC50 was 4.4 mg 1−1 for diazinon, 1.8 mg 1−1 for malathion, 3.5 mg 1−1 for fenitrothion oxon, and 0.16 0.22 mg 1−1 for diazinon oxon, 0.28 mg 1−1 for malaoxon, 6.8 mg 1−1 for fenitrothion oxon, and 0.16 mg 1−1 for EPN oxon. The bioconcentration factors (BCF) of diazinon oxon 0.5, malaoxon 1.1, fenitrothion oxon 2.3 and EPN oxon 11 in the whole body of the fish were much lower than those of diazinon 49, malathion 11, fenitrothion 122 and EPN 1124. As reference data, partition coefficients between n-octanol and water (Pow) were measured for these chemicals. The BCF values of each pesticide and its oxidation product were consistent with Pow values. The excretion rate constants (k) from the whole body of the fish were 0.12 hr−1 for diazinon, 0.27 hr−1 for malathion, 0.11 hr−1 for fenitrothion, 0.02 hr−1 for fenitrothion oxon and 0.59 hr−1 for EPN oxon. The rates of diazinon oxon and malaoxon could not be measured, but were presumed to be as rapid as or more rapid than those of fenitrothion oxon and EPN oxon. The results suggest that the contamination of fish and other aquatic organisms by the oxidation products in the environment is very low.