Bioaccessibility Of Dioxin Like Compounds In Foods And Their Application To Dietary Exposure Assessment

In present thesis, an in vitro gastrointestinal tract model based on Holland RIVM method was employed to simulate the release of dietary dioxin contaminants in the gastrointestinal tract and determine the concentrations of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in digestive juice. In comparison with their original concentrations in foods, we obtained the bioaccessibility (Bac%) of PCB and PCDD/F in different foods with the influence of different cooking methods, which provides operable data for the dietary exposure assessment of POPs. Considering recent monitoring results of relevant contaminants, we finalized the corrected Bac% and related dietary exposure results and compared total dietary exposure results observed between the year 2000 and 2007.The present thesis consists of the following five sections:1. Current in vivo and in vitro research progress on the bioaccessibility of POPs in both domestic and international studies has been comprehensively reviewed.2. A sensitive method based on programmable temperature vaporization large volume injection coupled with gas chromatography and high-resolution mass spectrometry (PTV-GC-HRMS) has been developed for the determination of ultra-trace levels of dioxin-like polychlorinated biphenyls(DL PCB) in small amount samples. Good linearity was achieved when the injection volume varied from 2 μL to 40 μL Using this analytical method, the requirement of blood sample amounts could be reduced to 1-2 mL from 10 mL so that the method sensitivity was greatly improved. This method provides substantial supports for small-amount sample analysis and metabolic analysis of PCB and PBDE.3. The author established an in vitro gastrointestinal tract model based on Holland RIVM method and investigated the effect of different cooking conditions on the bioaccessibility in various foods. Finally, we obtained detailed bioaccessibility data for the PCDD/F and PCB concentrations in various foods including rice, vegetable, milk, egg, beef and fish.For boiled rice, Bac% of PCDD/F and PCB range from 5 to 10% and 10 to 15%, respectively; for fried rice, Bac% of PCDD/F and PCB range from 15 to 20% and 30 to 85%, respectively. For boiled milk, Bac% of PCDD/F and PCB range from 25.73 to 30.50% and 28.46 to 95.56%, respectively. For boiled vegetable, Bac% of PCDD/F and PCB range from 0.3 to 3.4% and 2.0 to 7.7%, respectively; for fried vegetable, Bac% of PCDD/F and PCB range from 12.4 to 19.0% and 20.9 to 50.0%, respectively. For boiled egg, Bac% of PCDD/F and PCB range from 7.3 to 12.4% and 20.4 to 43.4%, respectively; for fried egg, Bac% of PCDD/F and PCB range from 11.0 to 23.5% and 39.4 to 85.0%, respectively. For boiled beef, Bac% of PCDD/F and PCB range from 5.9 to 12.1% and 41.4 to 59.0%, respectively; for fried beef, Bac% of PCDD/F and PCB range from 22.4 to 31.4% and 69.4 to 85.0%, respectively. For boiled fish, Bac% of PCDD/F and PCB range from 6.1 to 13.0% and 18.2 to 60.6%, respectively; for fried fish, Bac% of PCDD/F and PCB range from 19.9 to 36.6% and 59.4 to 103%, respectively.4. The author analyzed relevant data obtained from national food contaminants survey through 2009-2014, and estimated dioxin exposure levels in dairy products, pork, beef and fresh water fish. Considering the above analysis, dietary consumption and bioaccessibility parameters, we obtained corrected dietary exposure levels of dioxin like contaminants in local populations of Zhejiang province. The result shows the dietary exposure range from 13.0 to 41.8 pg TEQ/d.person, with a mean value of 27.4 pg TEQ/d.person, depending on different cooking conditions (boiling or frying), which is close to those of which were found in both 2000 and 2007 national total dietary survey (2000 TDS:29.3 pg TEQ/d.person; 2007 TDS:32.2 pg TEQ/d.person). These results indicate that current bioaccessibility parameters were comparable with the results from the Total Dietary Study and successfully used for the exposure assessment. Meanwhile, the present study is expected to be a powerful validation and potential supplement for the Total Dietary Study.5. The author investigated the analytical technology of OH-PCB from the metabolites of PCB. We optimized the derivatization conditions for the formation of MeO-PCB using TMSDM as the derivatization agent and finalized m/z parameters of various MeO-PCB and MeO-PBDE monomers during the isotope dilution high resolution mass spectrometry analysis. Finally, we conducted a chromatographic separation and obtained retention times of over 10 kinds of MeO-PCB using 60m DB-5 MS gas chromatograph column, which provides methodological basis for the metabolite analysis in tissue samples.