Bioaccessibility And Human Health Risk Assessment Of Arsenic In Soil,Shrimp And Rice

Arsenic(As), especially inorganic arsenic, is well known as a non-threshold,class 1 carcinogen. The predominant route for As exposure to humans is via oral ingestion. Therefore, it is important to accurately evaluate the health risk associated with oral exposure to As. To overcome the overestimation of risks based on total As concentration, bioaccessibility of As has been extensively used in human risk assessment. Thus, it is meaningful to systematically study the As bioaccessibility associated with oral exposure to As. However, few studies have focused on the regulations of As bioaccessibility and species after oral ingestion, not to mention the As metabolism of microbiota from human gut. Herein, a combined in vitro model which cultured the Chinese human gut microbiota was constructed, and As bioaccessibility, the changes of As species and human health risks were evaluated by using this combined model. The main conclusions are as follows:After incubation for 21 days, the constructed SHIME model reached stable. The gut microbiota mainly composed of Bacteroidetes, Proteobacteria, Firmicutes and Synergistetes, with various species up to 324 genus.The values of soil As bioaccessibility in gastric, small intestinal and colon phases were 13.84%±5.09%, 21.45%±10.62% and 17.65%±6.62%, respectively. The bioaccessibility of As was significantly(P<0.05) increased by human gut microbiota.Only inorganic arsenic(iAs) was detected in stomach and small intestine, with arsenate [As(V)] being the dominant As species. In colon phase,monomethylmonothioarsonic [MMMTA(V)] with unclear toxicological properties and monomethylarsonous acid [MMA(III)] with highly toxic were formed by human gut microbiota, which may result in the increase of potential risks.The values of shrimp As bioaccessibility in stomach, small intestine and colon phases were 79.48%±7.79%、87.08%±5.70% and 68.64%±19.71%, respectively.Nontoxic arsenobetaine [AsB] was the main As species, and a tiny amount of As(III)and As(V) was also observed in shrimps. In addition, the As species was not changedin colon phases, and there was no significantly difference in As bioaccessibility and species between boiled and fried shrimps.The values of rice As bioaccessibility in stomach and small intestine were56.18% ± 18.39% and 68.74% ± 18.98%, respectively. As(III) was the main As species in rice, and no As transformation was observed in digestive tract.The results of health risks evaluated by analyzing the As bioaccessibility was lower than that by analyzing total As concentrations. All of the values of Hazard Quotient(HQ) index were below 1, while the values of Carcinogenic Risk(CR) index were over the limited value(1.0×10-6). This indicated that the ingestion of As from soil, shrimp and rice would increased the carcinogen risks.