Evaluation of the risk of mixtures of paddy insecticides and their transformation products to aquatic organisms in the Sakura River, Japan

Abstract

To assess the risk of mixtures of six paddy insecticides and their transformation products (TPs) to aquatic organisms in the Sakura River, Japan, their concentrations in the river water were monitored during the rice cultivation season in 2008 and 2009, and acute toxicity tests for Cheumatopsyche brevilineata (caddisflies) and Daphnia magna (daphnids), surrogate test species for caddisflies and cladocerans, respectively, were conducted. The mixture of fipronil, applied in the rice nursery box, and its desulfinyl, sulfide, and sulfone TPs were detected in the river for several months after transplanting, and they were more toxic to C. brevilineata than the other tested compounds. The toxicities of the parent compound and its TPs, such as fipronil and its TPs, may be related to their hydrophobicities. Risk quotients for mixtures (RQ(mix)) of only parent compounds did not exceed 1, but, in mid-June 2009, the RQ(mix) of parent compounds and TPs for caddisflies exceeded 1. Diazinon, fenitrothion, and fenthion sprayed on the rice crop and their TPs posed a sporadic risk for cladocerans, depending on the application timing, whereas fipronil TPs contributed to the RQ(mix) for caddisflies for several months after transplanting. The risk of mixtures of insecticides and their TPs differed seasonally between caddisflies and cladocerans, depending on insecticide application timing and the persistence and toxicity of TPs.

Metabolism, bioaccumulation, and toxicity of pesticides in aquatic insect larvae

“…However, the risk quotient calculated from the monitored concentration and EC 50 of each metabolite with a safety factor of 10 did not exceed 1 for these mixtures in a Japanese river. 138) Two metabolites showed higher acute toxicity in many species of EPT compared to the parent fipronil, and a toxic concern for the most sensitive species (C. dilutes) was reported for the California creek receiving urban storm-water runoff. 118) Furthermore, periodical feeding should be conducted in a longer-term study to assess the effects of metabolites on growth where the dietary exposure to pesticides needs to be considered.…”

Strawberry fields forever? Urban agriculture in developed countries: a review

“…In an agricultural community in the suburbs of Tokyo, it was found that aerosols of organophosphate pesticide-infiltrated houses and childcare facilities located near farms and, depending on the nature of the pesticide, exposure from indoor air constituted a significant portion of the daily pesticide inhalation (Kawahara et al 2005). Surface runoff from agricultural pesticides has also contributed to the degradation of water quality and increased toxicity to aquatic organisms (Okamura et al 2002;Iwafune et al 2011). In addition, intensive fertilizer use has significantly increased nitrate concentrations in groundwater near tea plantations, orchards, vegetable fields, and livestock farms, including those areas in close proximity to urban centers (Kumazawa 2002;Gallardo et al 2005).…”

Behavior of nursery-box-applied fipronil and its sulfone metabolite in rice paddy fields

“…However, extensive use of fipronil may have unfavorable effects on nontarget aquatic organisms, and it has been reported to have a significant ecological impact on aquatic communities in paddy ecosystems (Hayasaka et al, 2012;Sánchez-Bayo et al, 2013). Fipronil and its metabolites have also been detected in aquatic environments, such as in the Sakura River, which flows through a region comprising many paddy fields, during the pesticide application period in May 2008 and 2009 in the Ibaraki prefecture, Japan (Iwafune et al, 2010(Iwafune et al, , 2011. Many studies have shown that fipronil sulfone, a fipronil metabolite, has a similar or even greater toxicity to aquatic invertebrates than the parent fipronil (Schlenk et al, 2001;Aajoud et al, 2003;Gunasekara et al, 2007).…”