Acute toxicity, accumulation and excretion of isoprothiolane and its degradation products in killifish

Acute toxicity, accumulation and excretion of isoprothiolane and its degradation products (isoprothiolane sulfoxide, diisopropyl chloromalonate and diisopropyl dichloromalonate) were studied for killifish (Oryzias latipes). The 48-h LC50 was 5.9 mg 1−1 for isoprothiolane, 35 mg 1−1 for isoprothiolane sulfoxide, 4.8 mg 1−1 for diisopropyl chloromalonate and 7.1 mg 1−1 for diisopropyl dichloromalonate. The toxicities of the isoprothiolane degradation products were nearly equal to or lower than that of isoprothiolane. The bioconcentration factors (BCF) in the whole body of the fish were 45 at low concentration and 40 at high concentration for isoprothiolane, 0.2 for isoprothiolane sulfoxide, 0.2 for diisopropyl chloromalonate and 0.7 for diisopropyl dichloromalonate. As reference data, partition coefficients between n-octanol and water (Pow) were measured for these compounds. Log Pow was 3.16 for isoprothiolane, 2.05 for isoprothiolane sulfoxide, 2.45 for diisopropyl chloromalonate and 3.44 for diisopropyl dichloromalonate. The excretion rate constants (k) from the whole body of the fish were 0.32 h−1 for isoprothiolane and 0.79 h−1 for diisopropyl dichloromalonate. The results suggest that the contamination of fish and other aquatic organisms by the isoprothiolane degradation products in the environment is low.