Abstract
Sumithion®, O, O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioate, at 0.1ppm or 0.02ppm in running water is readily taken up to rainbow trouts and southern topmouthed minnows. The content in fish reaches maximum after 1- to 3-day exposure, with bioaccumulation ratio of 200-250 depending on fish species, age and/or concentration in water. No increase in bioaccumulation ratio is observed on longer exposure. On transference of the fish to water stream free of Sumithion, the compound disappears quite rapidly from fish body and the content decreases to 1/1000 during 5 days. The radiotracer experiments afford the supporting evidences; Sumithion is metabolized in rainbow trouts to sumioxon, desmethylsumithion, desmethylsumioxon, 3-methyl-4-nitrophenol and its glucuronide, and these degradation products as well as Sumithion are eliminated from fish. These findings are discussed in comparison with those of p, p′-DDT in rainbow trouts, where DDT steadily accumulates with time and hardly disappears from fish body on transferring them to fresh water stream.
