ACUTE TOXICITY, ACCUMULATION AND EXCRETION OF ORGANOPHOSPHOROUS INSECTICIDES AND THEIR OXIDATION-PRODUCTS IN KILLIFISH

Acute toxicity, accumulation and excretion of four organophosphorous i nsecticides (diazinon, malathion, fenitrothion and EPN) and their oxid ation products (diazinon oxon, malaoxon, fenitrothion oxon and EPN oxo n) were studied for killifish (Oryzias latipes). The 48-hr LC50 was 4. 4 mg l(-1) for diazinon, 1.8 mg l(-1) for malathion, 3.5 mg l(-1) for fenitrothion, 0.58 mg l(-1) for EPN, 0.22 mg l(-1) for diazinon oxon, 0.28 mg l(-1) for malaoxon, 6.8 mg l(-1) for fenitrothion oxon, and 0. 16 mg l(-1) for EPN oxon. The bioconcentration factors (BCF) of diazin on oxon 0.5, malaoxon 1.1, fenitrothion oxon 2.3 and EPN oxon 11 in th e whole body of the fish were much lower than those of diazinon 49, ma lathion 11, fenitrothion 122 and EPN 1124. As reference data, partitio n coefficients between n-octanol and water (P-ow) were measured for th ese chemicals. The BCF values of each pesticide and its oxidation prod uct were consistent with the P-ow 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 EPN, 0.30 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 wer e 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 environme nt is very low. (C) 1997 Elsevier Science Ltd.