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In vitro modeling of the post-ingestion mobilization and bioaccessibility of pesticides sorbed to soil and house dust
Citation:
Starr, J., E. Valentini, B. Parker, S. Graham, AND F. Waldron. In vitro modeling of the post-ingestion mobilization and bioaccessibility of pesticides sorbed to soil and house dust. Society of Toxicology Annual Meeting, Nashville, TN, March 19 - 23, 2023.
Impact/Purpose:
Soils and house dusts are sorbents that can function as sinks for many regulated organic compounds. Since children ingest relatively large amounts of soil and dust, it is important to understand the factors that determine uptake of sorbed organic toxicants when estimating the toxicity of these chemicals to children. Considering ingestion of soil or house dusts with sorbed organics, bioaccessibility is defined as the percent of contaminant desorption from the soil or dust. In this study we develop an in vitro post ingestion bioaccessibility model for pesticides sorbed to soils and house dusts. The results show that bioaccessibility depends on the solubility of the pesticide and the carbon content of the soil or house dust. The data will be useful for pesticide risk assessments such as those done by Office of Pesticide Programs and those studying children's health such as Office of Children's Health Protection
Description:
Soils and dusts can act as sinks for semivolatile lipophilic organic compounds and children ingest relatively large amounts of both soils and dusts. Following intake, sorbed chemicals may desorb (mobilize) and become available for intestinal absorption (bioaccessible). For chemicals that are not degraded in the digestive tract, mobilization and bioaccessibility are the same. Where mobilized chemicals are degraded or lost it can be useful to separate mobilization from bioaccessibility. In this study we used a three-compartment in vitro assay to build digestive mobilization and bioaccessibility models for 16 pesticides (log Kow from 2.5 to 6.8) sorbed to 32 characterized soils and house dusts. Models were constructed both with and without a tenax sink meant to mimic intestinal absorption. We found that pesticide mobilization was predicted by pesticide log Kow and the carbon content of the soils and dusts. Pesticide loss measurably reduced the bioaccessibility of most pesticides, and bioaccessibility was largely predicted by log Kow and pesticide loss rate constants. Introduction of the sink increased mobilization by x? = 4 ± 6% (soil) and x? = 9 ± 7% (dust) and bioaccessibility x? = 41 ± 21% (soil) and x? = 24 ± 12% (dust). The results show that the physicochemical properties of the soils, dusts, and pesticides could be used to model in vitro pesticide mobilization and bioaccessibility.
