The Impact of Pesticides - Academy Publish

Fig. 3. Typical weekly variation of pesticide concentrations in Shin River,Niigata Prefecture (constructed based on Mitobe et al. 1999).PESTICIDES AND THEIR TRANSFORMATION PRODUCTSOrganophosphates and Their Sulfoxide OxonsSulfoxide oxons are typical transformation products of organophosphorus pesticides.The thiono (P=S) type organophosphates are easily oxidized to their oxono (P=O)type oxons by chlorination (Kamoshita et al. 2007, Onodera et al. 1976). The oxonsderived from the organophosphates have become a human health concern, becausesome oxons are reported to inhibit the acetylcholinesterase activity, and because thisinhibition was stronger than that caused by the parent organophosphate. Moreover,some oxons were degraded only slightly compared to the parent organophosphates.Therefore, they can remain in water for longer times than the organophosphates can(Arai et al. 2005).The concentrations of some oxons as well as the original organophosphates in riverwaters are presented in Table 3. Butamifos oxon, fenitrothion oxon, fenthion oxon,isoprothiolane oxon and Isoxathion oxon were detected in river waters together withtheir parent pesticides. In contrast, isoprothiolane oxon and tolchlofos methyl oxonwere only detected without their parent pesticides.Iwafune et al. (2010) reported that the ratios of fenthion oxon to fenthion were0.048-0.062 in Sakura River. The ratios of butamifos oxon to butamifos were 0.30-0.61 (mean 0.42) in the Shin River (Mitobe et al. 1999). Regarding fenthion, twoadditional transformation products, fenthion sulfone and fenthion sulfoxide, wereAcademyPublish.org - The Impact of Pesticides214