Residue And Dietary Risk Assessment Of Imidacloprid And Chlorfenapyr In Chieh-qua And Soil

In order to find out the safety of20%imidacloprid&chlorfenapyr suspension on chieh-qua, a field trial about the pesticide on chieh-qua was conducted in Guangzhou and Nanning in2012and2013. An analytical method for determination of imidacloprid and chlorfenapyr residue in chieh-qua and soil was developed in this study. The dissipation dynamic and terminal residue of imidacloprid and chlorfenapyr in chieh-qua and soil were studied, and the dietary risk assessment of imidacloprid and chlorfenapyr on chieh-qua was also evaluated. This paper provides a scientific basis for the rational use of20%imidacloprid&chlorfenapyr suspension, and has a realistic significance for protecting human’s health and environment. The results were as follows:(1) A simple and rapid method for determination of imidacloprid and chlorfenapyr in chieh-qua and soil sample was developed by liquid chromatography-tandem mass spectrometry. When spiked at0.01,0.10and1.00mg/kg, the average recoveries of imidacloprid were from103.1%to106.1%in chieh-qua with the relative standard deviation (RSD) from3.4%to7.4%, and from85.4%to107.7%in soil with RSD from6.3%to6.5%, respectively. The average recoveries of chlorfenapyr were from89.9%to110.3%in chieh-qua with RSD from2.8%to12.5%, and from80.4%to104.5%in soil with RSD from2.9%to11.1%, respectively.(2) Dissipation dynamic of imidacloprid and chlorfenapyr in chieh-qua and soil in Guangzhou and Nanning followed the first-order chemical kinetic equation Ct=CoE-Kt. The half lives of imidacloprid were from3.3to6.5days in chieh-qua and from5.5to7.6days in soil, respectively. The half lives of chlorfenapyr were from2.4to5.9days in chieh-qua and from2.8to9.4days in soil, respectively.(3) As3days,5days and7days after application, the terminal residues of imidacloprid were from0.01to0.21mg/kg in chieh-qua and from0.01to0.48mg/kg in soil, and that of chlorfenapyr were below0.46mg/kg in chieh-qua and below0.60mg/kg in soil, when applied at the maximum recommended dosage and1.5times that of20%imidacloprid&chlorfenapyr suspension concentrate with spraying1or2times at an interval of7days. According to the results, the reasonable suggestions were given for the use of20%imidacloprid&chlorfenapyr suspension on chieh-qua:the dosage was60to90g a.i/hm2, sprayed once with spraying interval of7days, and the interval to harvest was3days.(4) Under good agricultural practice, the supervised trials median residue (STMR) of imidacloprid was0.06mg/kg; the national estimated daily intakes (NEDIs) of imidacloprid were0.27-0.59μg·kg-1bw·d-1for all groups of Chinese residents, the percent ratios to acceptable daily intake (ADI) were0.45%-0.99%. The results showed that, the chronic intake risk of imidacloprid was acceptable for all groups of Chinese residents. Theoretical maximum daily intakes (TMDIs) of imidacloprid were2.27-4.93μ·gkg-1bw·d-1, the consumer protection level (CPL) of exiting imidacloprid MRL was12.16-26.40for all groups. The results indicated that, the CPL of exiting imidacloprid MRL0.5mg/kg was acceptable.(5) Under good agricultural practice, the STMR of chlorfenapyr was0.11mg/kg, the NEDIs of chlorfenapyr were0.50-1.09μ·gkg-1bw·d-1for all groups of Chinese residents, the percent ratios to ADI were16.67%-36.18%. The results showed that, the chronic intake risk of chlorfenapyr was acceptable for all groups of Chinese residents. TMDIs of chlorfenapyr were2.27-4.93μ·gkg-1bw·d-1, the CPL of chlorfenapyr MRL was1.08-1.32for the group over14years old and0.61-0.87for the rest groups. The results indicated that, the CPL of chlorfenapyr MRL0.5mg/kg was acceptable for the group over14years old, but unacceptable for the rest groups.