Pesticide Residues And Dietary Risk Assessment In The Processing Of Four Agricultural Products

Pesticides are indispensable in agricultural activities,in order to increase the yield and the quality of agricultural products,various pesticides are widely used to protect them against diseases,pests and weeds,.The application of pesticides inevitably cause pesticide residues in agricultural products,which may bring about potential risks to human health.In this study,rice,celery,onion and tea were selected as representative agricultural products to study the behaviour of pesticide residues during various processing,and the dietary risk assessment was conducted respectively,which could offer a valuable reference for reasonable usage of pesticides and various processing of agricultural products.A sensitive analytical method for determination of 68 pesticides and some metabolites residue in unhusked rice,rice and Chinese Baijiu was established and validated.Outstanding linearities were observed for the selected 73analytes in all matriceswith the coefficients of determination(R~2)larger than 0.9912.The LODs were between 0.1?g/kg and 2.9?g/kg,and the LOQs wasbetween 0.2?g/kg and 8.4?g/kg for the pesticides in three matrices.To assessthe accuracy and precision,recovery experiments were carried out for each matrix in quintuplicate at 0.01,0.1and 0.5mg/kg spiked levels,the average recovery rates of the pesticides ranged from62%to 118%with the RSDs lower than 14.7%.Therefore,this method was and suitable for residue analysis of relevant pesticides propiconazole unhusked rice,rice and Chinese Baijiu.The fate of 35 pesticides and some of the metabolites in field incurred rice samples during Chinese Baijiu production was systematically studied.The removal effect of pesticide residues in the process of soaking is related to the physicochemical properties such as the solubility of pesticides in water and octanol-water partition coefficient.,the removal effect was more obvious because of the higher solubility in water;during the steaming progress,the constant heating could enhance evaporation or thermal degradation and result in the reduction of pesticide residues and could convert residues to more toxic metabolites.Microorganisms in the fermentation process also have a certain degradation effect on pesticide decrease;distillation can effectively reduce the level of pesticide residues in Chinese Baijiu,and the migration rate may be related to the vapor pressure.The pesticides may easily distilled from the mash into the Chinese Baijiu with high vapor pressure.During the entire process,14 pesticides were completely removed.The processing factors of the remaining 21 pesticides in the process were between 0.0003and 0.054,and the migration rate of pesticides from rice to Chinese Baijiu was less than 1.26%,indicating the migration risk is low,and pesticide residues could be reduced obviously during the production of Chinese Baijiu from rice.The changes of 18 pesticide residues and processing factors during rice processing and cooking were studied.After the rice is harvested,the removal rate of18 pesticide is larger than 90%through the processes of hulling,rice milling,panning,and cooking.The residues of penoxsulam are completely removed during the whole process,and processed factors of the remaining 17 pesticides is between0.002 and 0.022,indicating that the processing and cooking step could remove most of the pesticide residues in the rice.The degradation behaviors and residue distributions of propiconazole in celery and onion under field trials were studied.The half-lives of propiconazole in onions and celery were 6.1-6.2 days and 8.7-8.8 days,respectively.The final residues of propiconazole in celery and onions are 0.404 mg/kg-10.3 mg/kg and<0.002mg/kg-0.037 mg/kg,serving as a reference to for the establishment maximum residue limits of propiconazole in celery and onions in China.By simulating field experiment samples,the effects of different washing and cooking methods on the changes of four pesticide residues in celery were studied.The removal rate is related to the kind of cleaning solvent,cleaning time,water solubility,octanol-water partition coefficient(log Kow)and other properties of pesticides.The processing factors of the four pesticides were between 0.05-0.33 during the entire process which manifested the pesticide residues in celery could be Significantly reduce by cleaning and cooking.The result offers certain guiding significance for daily washing and cooking.The residual changes of tolfenpyrad and dinotefuran and its metabolites DN and UF in the process of tea planting and brewing were studied under field trials.The half-lives of tolfenpyrad and dinotefuran in fresh tea were 4.30-7.73 days and4.65-5.50 days.With the extension of sampling time,DN and UF in tea showed a trend of first increasing and then decreasing.The final residues of tolfenpyrad and dinotefuran in made tea are 1.59 mg/kg-19.6 mg/kg and 0.556 mg/kg-7.13 mg/kg,respectively,which are lower than the maximum residue limits established in China.In the tea brewing test,with the increase of leaching times,the leaching rate gradually decreased.After 3 times of brewing,the leaching rates of tolfenpyrad and dinotefuran were 1.4%-2.3%and 93.7%-98.1%,respectively.The leaching rate of pesticides in tea infusion is mainly due to its physicochemical properties such as water solubility and octanol-water partition coefficient.Pesticides with low water solubility and high octanol-water partition coefficient are easily removed from the made tea to tea infusion during the brewing process and beneficial to reduce the dietary intake risk.Based on the pesticide residues in the market survey of rice and Chinese Baijiu,and field trials in celery,onion and tea,chronic and acute dietary risks have been assessed for the corresponding pesticides.The RQ_cof the pesticides in rice were less than 33.7%,respectively,which indicating that the detected pesticide residues are acceptable to consumers.The RQ_cof propiconazole,tolfenpyrad and dinotefuran are9.8%,37.6%and 24.7%,the RQ_aof propiconazole in celery and onion are less than5.0%and 0.036%,and the RQ_aof dinotefuran and tolfenpyradin tea is less than 5.4%and 0.84%,respectively.It indicated that,in the practice of using propiconazole,tolfenpyrad and dinotefuran under recommended application dosage,the produced agricultural products usuallydo not cause unacceptable health risks to the general consumers.