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Residue behavior and risk assessment of thiamethoxam in sugarcane and soil
  • Residue behavior and risk assessment of thiamethoxam in sugarcane and soil

Residue behavior and risk assessment of thiamethoxam in sugarcane and soil

Key words:thiamethoxam;metabolite clothianidin;sugarcane;soil;residue behavior;risk assessment
Details
Abstract:【Objective】Residue and degradation dynamic of thiamethoxam on sugarcane and soil were determined in this study,the health risk to consumers and environment risk to non-target organism earthworm in soil were also assessed according to the residues of thiamethoxam,the results would provide references for the rational use of thiamethoxam on sugarcane.【Method】The residue degradation dynamic and final residue experiments of 10% thiamethoxam granule in sugarcane and soil were conducted in Hainan and Guangxi during 2015 and 2016,the acute and chronic dietary exposure risk to human and environment risk to non-target organism earthworm were also assessed according to the residues of thiamethoxam and metabolite clothianidin in sugarcane stalk and soil respectively.【Result】Results of residue degradation dynamic experiments showed the half-lives of thiamethoxam were 8.4-18.2 d and 17.3-22.4 d in sugarcane plant and soil respectively. Final residue experiments showed the final residue of thiamethoxam and its metabolite clothianidin in sugarcane shoot
and stalk were all below limit of quantitation(LOQ)(0.05 mg/kg),but at the high dosage of 562.5 g a.i/ha,the final residues of thiamethoxam in soil were higher than LOQ and up to 0.146-0.153 mg/kg at harvest time. The results of dietary exposure risk assessment showed the estimated daily intakes(EDI)of thiamethoxam and clothianidin were just 0.0039%- 0.0049% of the acceptable daily intake(ADI)to the general people while the estimated short-term intakes(ESTI)were just 0.17%-0.29% of the acute reference dose(ARfD). The results of environment risk assessment showed the risk quotient(RQ)of thiamethoxam to earthworm was below 0.01 while it was 0.016 for clothianidin.【Conclusion】After furrow application of 10% thiamethoxam granule at 375.0-562.5 g a.i/ha for once-twice at sugarcane seedling stage,the final residue of thiamethoxam and clothianidin in sugarcane are under the maximum residue limit(MRL)of China and Code AlimentariusCommission(CAC),and the acute and chronic dietary exposure risk of residues to human health are within the acceptable limit. However,it is recommended to note the environmental risk of the metabolite clothianidin to the non-target organism earthworm in soil when the product is registered for use on sugarcane.




A:Blank plant;B:Plant spiked with 0.05 mg/kg thiamethoxam;C:Blank stem;D:Stem spiked with 0.05 mg/kg thiamethoxam;E:Blank shoot;   F:Shoot spiked with 0.05 mg/kg thiamethoxam


                                        A:Blank soil;B:Soil spiked with 0.05 mg/kg thiamethoxam


              A:Blank plant;B:Plant spiked with 0.05 mg/kg clothianidin;C:Blank stem;D:Stem spiked with 0.05 mg/kg       clothianidin;E:Blank shoot;F:Shoot spiked with 0.05 mg/kg clothianidin;G:Blank soil;H:Soil spiked with 0.05 mg/kg clothianidin