| BackgroundPerchlorate（ClO4-）is a persistent inorganic pollutant that can be concentrated in food through the food chain and thus endanger food safety and human health through the food chain.Diet has been shown to be the main route of human exposure to perchlorate.Now,the main dietary exposure assessment focuses more on the external exposure level after the intake of food,ignoring the differences in food substrate and the influence of perchlorate bioaccessibility and bioavailability.Infants and young children are at high risk of exposure to pollution,The level of health hazards caused by perchlorate should arouse the special attention of the public.It has great scientific and practical significance to comprehensively evaluate the risk of perchlorate in infant food to infant population and further evaluate the bioaccessibility and bioavailability of perchlorate in different food substrates.MethodEstablishing the isotope dilution liquid chromatography tandem mass spectrometry（LC-MS/MS）to detect the content of perchlorate in infant milk powder and supplementary food.The RIVM digestion model factors of perchlorate in three food substrates（lettuce,rice and milk powder）were optimized to simulate gastrointestinal digestion under optimal conditions,and the maximum bioaccessibility of perchlorate in different food substrates was obtained.A caco-2 cell intestinal absorption model was constructed and RIVM in vitro digestion method was used to analyze the transmembrane transport mechanism and bioavailability parameters of perchlorate in different food substrates,to assess the risk level of perchlorate exposure in representative foods for infants and young children based on their bioavailability parameters.Result1.Analysis and detection of perchlorate in infant food and risk assessment of exposureThe detection limit of this method was 0.02 g/kg,the recovery was 80.0%109.2%,and the RSD was within the allowable error range.The detection results of perchlorate in seven categories of infant food on the market showed that the detection concentration of perchlorate ranged from 0.1 to 103.34μg/kg,and the detection rate reached 85.3%.The average content of perchlorate in milk powder,rice powder and domestic infant noodle food was higher than other types of food.The exposure level of perchlorate in infants ranged from 0.00 to 0.28μg/kg bw/day,and the exposure level of first stage infant formula was 0.28μg/kg bw/day,and the lowest exposure level was food nutrition supplement.The exposure contribution rate of perchlorate of milk powder and rice powder decreased gradually with the growth of infant age,while that of other kinds of food,especially noodles and vegetable puree,increased steadily.2.Bioaccessiblity of perchlorate in different food substratesThe optimal conditions for pH,digestion time and digestive liquid volume of lettuce,rice and milk powder in oral cavity were 6.2,6.2,7.1;6 min,5.5 min,7 min;8 mL,6 mL,7 mL respectively.The optimal digestion conditions in the stomach were 2.5,3,2.5;3 h,2h,1 h;11 mL,12 mL,11 mL.The optimal digestion conditions in the intestinal tract were6.0,5.5,6.5;2.5 h,2 h,3 h;11+5.5 mL,11+5.5 mL,14+7 mL.After digestion using the optimized in vitro RIVM model,the maximum bioaccessibility parameters of different food substrates in each digestion chamber were obtained by comparing with the control group.The bioaccessibility of lettuce,rice and milk powder were:（68.23±2.06）%,（68.27±3.45）%and（58.70±2.86）%respectively.3.In vitro bioavailability and transport mechanisms of perchlorate in food substratesThe Caco-2 intestinal absorption and transport model established in the experiment met the requirements of the transport experiment.Compared with the final transmissibility of three different food substrates,the size relation of perchlorate absorption in the gastrointestinal tract was successively:rice>lettuce>milk powder>control.The absorption level of perchlorate in the body reached more than 20%,which belongs to the absorption of general substances and its transport between intestinal epithelial cells is likely to be passive diffusion.The in vitro bioavailability of perchlorate in lettuce,rice and milk powder was（34.5±1.0）%,（37.9±1.9）%and（26.2±1.3）%respectively,both higher than sodium perchlorate control group（23.6±1.2）%.At the same time,the in vitro bioavailability of rice and milk powder group was significantly higher than that of sodium perchlorate control group（P<0.05）.The results showed that perchlorate in food matrix was more easily absorbed by human body in small intestine than pure sodium perchlorate.Based on the bioavailability in vitro,the evaluation results of the exposure level of perchlorate showed that the exposure level and risk quotient of milk powder and rice in the first,second and third stages were decreased,but milk powder was still the main risk factor of perchlorate in infant food.ConclusionThe risk level of perchlorate exposure in infant group is within the safe range.However,the HQ value of the first and second stage milk powder is 0.95 and 0.91respectively,which is close to 1.The risk of infant milk powder exposure to perchlorate should be of concern to researchers.The presence of food matrix can promote the release ratio of perchlorate ions in the digestive juice and the bioaccessibility sizes are:rice>lettuce>milk powder.The absorption of perchlorate on caco-2 cells in different food substrates was significantly different,and the bioavailability was in order:rice>lettuce>milk powder.Milk powder is still the main risk factor of perchlorate in infant food. |
