Oral Bioaccessibility of Dioxins/Furans at Low Concentrations (50−350 ppt Toxicity Equivalent) in Soil

Abstract

Animal studies have indicated that the oral bioavailability of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in environmentally contaminated soil could range from 0.5 to 60%. To estimate the oral bioavailability of TCDD, and the 16 other 2,3,7,8-substituted dioxin/furan congeners, this study used a physiologically based extraction test, designed around the anatomic and physiologic characteristics of the human digestive tract. This test measures the fraction of dioxins/furans in soil that would be solubilized in the gastrointestinal tract (i.e., that would be bioaccessible) and therefore available for absorption. Eight soils from Midland, MI, were evaluated in this study and exhibited TCDD concentrations of 1.7-139 pg/g (ppt) and total TEQ concentrations of 6-340 ppt. Bioaccessibility of dioxins/furans from these soils ranged from 19 to 34% averaged across the 17 2,3,7,8-substituted dioxin/furan congeners), with an average of 25%. The total organic carbon in these soils was low--ranging from 1 to 4%--particularly for the soil series from which they were collected. Bioaccessibility of individual congeners did not appear to be correlated with degree of chlorination. Even though these dioxin/furan concentrations are much less than studied previously, these results are consistent with those from animal studies at other sites, which have generally yielded values of 20-60% relative bioavailability for TCDD in soil.

Bioavailability of Soil-Borne Chemicals: Abiotic Assessment Tools

“…PBET methods have been published for PAHs (Hack and Selenka 1996;Guha et al 1998;Holman 2000), PCBs (Hack and Selenka 1996;Oomen et al 2000), lindane (Oomen et al 2000), and dioxins/furans (Wittsiepe et al 2001;Ruby et al 2002) in soil. Bioaccessibility of these HOCs from soil has generally been less than 50%, and has varied considerably, depending on the composition of the extraction fluid.…”

Arsenic relative bioavailability from diet and airborne exposures: Implications for risk assessment

“…Multiple versions of the in vitro test system have been developed; gastric and intestinal phases are included in most protocols with varying compartment constituents among methods (Ng et al, 2013). Digestive enzymes (e.g., pepsin) mucins, proteins, lipids, and selected intestinal microbes may be included in the gastric phase, whereas bile and pancreatin are usual constituents of the gastric phase (Charman et al, 1997;Dean and Ma, 2007;Molly et al, 1993;Oomen et al, 2003Oomen et al, , 2004Ruby et al, 2002;Tang et al, 2006). Incorporation of a microbial component has not been found to affect As bioaccessibility estimates consistently compared with methods that do not include microbial activity (Laird et al, 2009(Laird et al, , 2013.…”

Exposure assessment at a PCDD/F contaminated site in Sweden—field measurements of exposure media and blood serum analysis

“…It is conceivable that the intestinal tract availability of PCDD/Fs from a particulate matrix (e.g., soil and groundwater particles) is lower than for, e.g., fatty food (Budinsky et al 2008;Ruby et al 2002), and the real risk associated to soil and groundwater ingestion is possibly lower than indicated in Table 7. The pulmonary availability of 2378-TCDD was found to be high (95%; Diliberto et al 1996), and thus, the inhalation exposure pathway may be critical for the total internal dose.…”