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The concentrations of PBDEs in 299 vegetable and animal-based food samples of 31 species, collected in Shanghai, China, and the bioaccessibility of PBDEs in part of the samples were determined. The PBDE concentrations ranged from 0 to 1245.4pgg(-1) with animal-based food containing more PBDEs than vegetables. The bioaccessibility of PBDEs, determined by a method simulating human gastrointestinal digestion process, were from 2.6% to 39.9% in vegetables, and from 5.2% to 105.3% in animal-based food. For animal-based food, good correlations were observed between the bioaccessibility of PBDEs and the fat content, thus the fat content in animal-based food was able to be used to estimate the bioaccessibility of PBDEs. The total daily intake of PBDEs via ingestion of vegetables and animal-based food for an average Shanghai resident was estimated as 13235.7 and 13668.0pg d(-1), respectively, but the amounts available for human absorption were reduced to 2674.4 and 4316.6pgd(-1) after the PBDE bioaccessibility was considered. Finally, the contributions of different food groups to the total daily intake of PBDEs were evaluated. The results revealed that, when not considering the bioaccessibility of PBDEs, vegetables were the leading contributor (49.2%), followed by fish (34.0%). However, the sequence was reversed after the PBDE bioaccessibility was taken into account. The results indicated that human exposure to PBDEs via food ingestion might have been significantly overestimated and the exposure assessment could be misleading if the bioaccessibility of PBDEs was not considered.

Bioaccessibility of a contaminant in foods is the fraction of the contaminant mobilized from the food matrices during gastrointestinal digestion. In the present paper, the bioaccessibility of polybrominated diphenyl ethers (PBDEs) in 13 types of foods, including fish, meat, rice, flour, and vegetables, was determined using an in vitro digestion method. The bioaccessibility obtained ranged from 2.6% to 41.3%. It was found that the bioaccessibility of PBDEs exhibited positive correlations with fat and carbohydrate contents and negative correlations with protein and dietary fiber contents in the foods. Fat was the most important factor affecting the bioaccessibility of PBDEs. The mechanism underlying the correlations was discussed in view of partition of PBDEs between liquid and solid phases. To our knowledge, this is the first article systematically investigating the bioaccessibility of PBDEs in foods and demonstrating the influence of the food constituents on the bioaccessibility of PBDEs.

Compound-specific carbon isotope ratio analysis is a promising tool to assess the origins and fates of organic contaminants in many fields. The present study aims to investigate the isotope effects of dichloro-diphenyl-trichloroethane (DDT) and its degradates in carrots during digestion processes simulating the human gastrointestinal tract. To accurately interpret isotopic data obtained for unreleased DDTs (p,p-DDT, p,p-DDD and p,p-DDE) from carrots during digestion, spiked carrots with known d 13 C values of DDTs were incubated in simulated gastric and intestinal solutions using a static in vitro model of the human gut. The d 13 C values and concentrations of DDTs remaining in the carrot and in the digestive solutions were measured. The difference in the d 13 C values of the added DDTs and the matrix-bound DDTs after digestion was always

A static in vitro digestion model simulating human gastrointestinal tract was used to investigate digestion mechanism of polychlorinated biphenyls (PCBs) in food during digestion. The results showed that the release process of PCBs from food matrix conformed by the pseudo-second-order kinetic model at non-equilibrium condition and reached equilibrium after 2h in small intestine, while the adsorption and release processes at equilibrium were follow Langmuir isotherm equation (R 2 > 0.99). The study results also demonstrated that the relationship between the released PCBs and their levels in food is a partitioning-based model, and has nothing to do with their contamination levels. The present study provides basic information for advanced in vitro and in vivo studies on the mechanism or uptake of PCBs or other chemicals in human body.

Factors affecting the bioaccessibility of PCBs in food matrix during digestion were investigated using a static in vitro digestion model simulating human gastrointestinal (GI) tract. The results showed that the ratios of digestive juice to the mass of food (L/M), the pH values of the digestive juice and the ageing time of PCBs in food matrix had significant effect on it. The PCBs bioaccessibility increased with the L/M ratio and the pH values increasing, while it decreased with the ageing time prolong. The present study provides basic information for advanced in vitro studies on the bioaccessibility of PCBs in human body.

The factors affecting the bioaccessibility of polybrominated diphenyl ethers (PBDEs) in foodstuffs were investigated using a static in vitro model. The results showed that the gastrointestinal digestion increased the bioaccessibility of PBDEs in the intestinal solution. The incubation time significantly affected the bioaccessibility, which increased to about 25% in 4-6 h and reached equilibrium. The adsorption and release processes followed a Langmuir isotherm equation (R(2)0.99). The concentrations of PBDEs in foodstuffs did not affect the bioaccessibility, while the ratios of liquid to the mass of foodstuffs had a significant effect when the ratios were less than 90. The bioaccessibility of PBDEs increased with increasing pH, reached a maximum at a pH of 7.3 +/- 0.1, and then decreased in the intestine. To our knowledge, this is the first report demonstrating the digestive parameters playing such an important role for the bioaccessibility of PBDEs in foodstuffs. Even though in vitro tests are often conducted to study bioaccessibility, the extrapolation of such results to explain what is happening inside the highly dynamic environment of the human gastrointestinal tract is still sometimes uncertain and sometimes underestimated.