In vitro oral bioaccessibility investigation and human health risk assessment of heavy metals in wheat grains grown near the mines in North China.

There is limited research on the effects of gut microbiota on bioaccessibility of heavy metals in wheat grains. In this study, bioaccessibility of heavy metals (Cu, Cd, Pb, and Zn) in wheat was determined to elucidate transfer characteristics in the soil-grain-human systems near two large-scale mining areas in Shandong Province, North China using the physiologically-based extraction test (PBET) in combination with a simulator of human intestinal microbial ecosystems (SHIME). The results showed the bioconcentration factors (BCFs) of Cu, Cd, Pb, and Zn were 0.123-0.327, 0.188-0.478, 0.019-0.099, and 0.262-0.825, respectively. Significant and positive correlations were observed between heavy metals in soils and wheat grains. In the simulated colon phase, bioaccessibility of Cd and Zn significantly decreased to 7.81% and 8.81%, respectively, being 53% and 64% of that in the simulated small intestinal phase. However, bioaccessibility of Pb showed an obvious escalating trend, being 2.4 times higher than that of intestinal incubation. Based on the estimated daily intakes and contribution, the relative high contribution of Cu to the benchmark dose in both phases, Cu metabolism by human gut microbiota should be considered in human health risk assessment regarding wheat consumption.