Oral Bioavailability of Polychlorinated Dibenzo-p-Dioxins/Dibenzofurans in Industrial Soils

Abstract

In this study, the oral bioavailabilities of numerous 2,3,7,8-PCDD/F congeners were evaluated in soil samples from an industrial site. The purpose of this study is several-fold: (1) to compare the soil bioavailability results of the different PCDD/F congeners; (2) to evaluate the consistency of the bioavailability results with those obtained in an in vitro bioaccessibility study with simulated GI tract fluids; and (3) to develop quantitative bioavailability measurements that are appropriate for use in a health risk assessment for this site. Soil samples containing PCDD/F toxic equivalent (TEQ) concentrations ranging from 0.53-45.2 ng/g were administered to female Sprague Dawley rats via oral gavage. Reference formulations of PCDD/Fs were administered intravenously or by oral gavage. The overall relative bioavailability of PCDD/Fs in the soil samples on a TEQ basis ranged from 17 to 51%, with a mean of 38%. The results of the in vitro bioaccessibility study were consistent with the bioavailability results (mean extracted TEQ of 22%). Because of the clear relationship between increasing chlorination and decreasing bioavailability and bioaccessibility observed in this study, we suggest that simply extrapolating results from one congener to another may be associated with a high degree of uncertainty.

Bioaccessibility Extractions for Contaminant Risk Assessment

“…Particle size, specifically the fraction of the sample that passes through a defined sieve size (e.g., <250 mm), is prescribed in some methods, and has been proposed to be relevant to the method development of bioaccessibility extractions. 89,[159][160][161][162][163] To advance the appropriate selection of sieved particle size, research should address the link between sieved particle size and mean particle size. For example, the discrepancy between particle size, which is defined by a particular sieve size, and the parameter considered to be relevant for risk assessment, which is the mean particle size that adheres to human hands, is not usually considered.…”

Selective Soil Particle Adherence to Hands: Implications for Understanding Oral Exposure to Soil Contaminants

“…U.S. EPA has also developed a swine model for determination of relative arsenic bioavailability from soil, which uses a <250 μm soil fraction . U.S. EPA’s selection and use of the <250 μm soil fraction most likely influenced later research groups, which generally have used the <250 μm particle size for oral bioavailability research models (Maddaloni et al, lead in humans; Roberts et al, arsenic in primates; , Budinsky et al, dioxins/furans in rats and swine; Finley et al, dioxins/furans in rats). Recently, James et al developed a swine model for PAH bioavailability from soil using a <45 μm soil fraction .…”

Lead and Arsenic Bioaccessibility and Speciation as a Function of Soil Particle Size

“…Since the 1990s, USEPA utilized a swine model for the determination of relative Pb and As bioavailability from soil, which uses a <250‐μm soil fraction (USEPA, 2005). Thereafter, most researchers have used the <250‐μm particle size for oral bioavailability research models (Maddaloni et al, 1998, Pb in humans; Roberts et al, 2007, As in primates; Budinsky et al, 2008, dioxins and furans in rats and swine; Finley et al, 2009, dioxins and furans in rats; Casteel et al, 2006, and Denys et al, 2007, Pb and As in juvenile swine; Bradham et al, 2011, 2013, 2015, As in mice).…”