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Is food type important for in vitro post ingestion bioaccessibility models of polychlorinated biphenyls sorbed to soil?
Citation:
Starr, J., W. Li, S. Graham, H. Shen, AND F. Waldron. Is food type important for in vitro post ingestion bioaccessibility models of polychlorinated biphenyls sorbed to soil? 2019 American Chemical Society Fall Meeting, San Diego, CA, August 25 - 29, 2019.
Impact/Purpose:
Soils are sorbents for many regulated organic compounds and children consume relatively large amounts of soil. To better the estimate the risk from this exposure pathway, requires an understanding of the behavior of sorbed chemicals following soil ingestion. We examined the role of co-ingested foods in determining the post-ingestion bioaccessibility (mobilization) of 18 polychlorinated biphenyls (PCBs) sorbed to 10 characterized soils. Across all treatments, percent soil carbon was the primary bioaccessibility determinant, accounting for ≥ 87% of the explained variation. All sink materials (protein, bile, and fat), effectively increased PCB bioaccessibility and reduced freely dissolved PCB concentrations. This suggests competitive removal of desorbed PCBs. Without sink material, intra-PCB mobilization differences were observed as freely dissolved PCB concentrations correlated (negative, p < 0.05) with their respective log Kow's, When added to the complete digestive fluid, increasing oleic acid mass increased PCB bioaccessibility (p 0.05). This indicates that fat intake may be the sole consideration when modeling dietary contributions to bioaccessibility of soil sorbed PCBs.
Description:
Soils are sorbents for many regulated organic compounds and children consume relatively large amounts of soil. To better the estimate the risk from this exposure pathway, requires an understanding of the behavior of sorbed chemicals following soil ingestion. We examined the role of co-ingested foods in determining the post-ingestion bioaccessibility (mobilization) of 18 polychlorinated biphenyls (PCBs) sorbed to 10 characterized soils. The bioaccessibility test system (DIN 19738, 2004) was an in vitro, 3-compartment, digestive tract containing salts, protein, and bile. Each soil was fortified with PCBs, then, digestive fluids appropriate to each compartment, were added sequentially. Next, digestive fluid and soil were seperated and PCB concentrations in both were measured. Bioaccessibility was defined as percent of each PCB in the fluid. The “complete” assay was then reduced to assess contributions of individual endogenous digestive fluid constituents (water, salts, pancreatin, bile, and mucin), and representative foods: protein (bovine serum albumin (BSA)), sugar (glucose), and fat (oleic acid). Finally, increasing concentrations of BSA, glucose, and oleic acid were added (individually) to “complete” test systems. In a subset of the samples, solid phase microextraction (SPME) measured freely dissolved PCBs. Across all treatments, percent soil carbon was the primary bioaccessibility determinant, accounting for ≥ 87% of the explained variation. All sink materials (protein, bile, and fat), effectively increased PCB bioaccessibility and reduced freely dissolved PCB concentrations. This suggests competitive removal of desorbed PCBs. Without sink material, intra-PCB mobilization differences were observed as freely dissolved PCB concentrations correlated (negative, p < 0.05) with their respective log Kow's, When added to the complete digestive fluid, increasing oleic acid mass increased PCB bioaccessibility (p 0.05). This indicates that fat intake may be the sole consideration when modeling dietary contributions to bioaccessibility of soil sorbed PCBs.
