Benzo[a]pyrene bioavailability from pristine soil and contaminated sediment assessed using two in vitro models

Abstract

A major route of exposure to hydrophobic organic contaminants (HOCs), such as benzo[a]pyrene (BaP), is ingestion. Matrix-bound HOCs may become bioavailable after mobilization by the gastrointestinal fluids followed by sorption to the intestinal epithelium. The purpose of this research was to measure the bioavailability of [14C]-BaP bound to pristine soils or field-contaminated sediment using an in vitro model of gastrointestinal digestion followed by sorption to human enterocytes (Caco-2 cells) or to a surrogate membrane, ethylene vinyl acetate (EVA) thin film. Although Caco-2 cells had a twofold higher lipid-normalized fugacity capacity than EVA, [14C]-BaP uptake by Caco-2 lipids and EVA thin film demonstrated a linear relationship within the range of BaP concentrations tested. These results suggest that EVA thin film is a good membrane surrogate for passive uptake of BaP. The in vitro system provided enough sensitivity to detect matrix effects on bioavailability; after 5 h, significantly lower concentrations of [14C]-BaP were sorbed into Caco-2 cells from soil containing a higher percentage of organic matter compared to soil with a lower percentage of organic matter. The [14C]-BaP desorption rate from Caco-2 lipids consistently was twofold higher than from EVA thin film for all matrices tested. The more rapid kinetics observed with Caco-2 cells probably were due to the greater surface area available for absorption/desorption in the cells. After 5 h, the uptake of BaP into Caco-2 lipid was similar in live and metabolically inert Caco-2 cells, suggesting that the primary route of BaP uptake is by passive diffusion. Moreover, the driving force for uptake is the fugacity gradient that exists between the gastrointestinal fluid and the membrane.

Assessment of the bioaccessibility of polycyclic aromatic hydrocarbons in topsoils from different urban functional areas using an in vitro gastrointestinal test

“…The surrogates containing d 10 -acenaphthene, d 10 -phenanthrene, d 12 -chrysene, and d 12 -perylene were purchased from Aldrich Chemical (USA). The spiking process was according to the method described by Vasiluk et al (2007). Soil (5 g) was put into a 50-mL cleaned glass vial to which 10 μL 20 mg/L mixed surrogates were added.…”

Impact of reference geosorbents on oral bioaccessibility of PAH in a human in vitro digestive tract model

“…Former studies on soil samples suggested soil organic carbon (SOC) to be one reason for variable PAH bioaccessibility (Hack and Selenka 1996;Lu et al 2010;Pu et al 2004;Tao et al 2010;Vasiluk et al 2007). Grøn et al (2007) and Hansen et al (2007) estimated maximum bioaccessibility (25-40 %) at lowest "humic content" (2 %) and lower bioaccessibility (6-24 %) at 4-5 % "humic content."…”

Health risk assessment of mixed contaminants: Interaction of metals on the uptake of polycyclic aromatic hydrocarbons in human liver cells

“…There are few studies in literature that have investigated bioavailability of organic contaminants including PAHs by use of in vitro gastrointestinal digestion of spiked soils in combination with Caco-2 cells Vasiluk et al, 2007). In this Chapter the availability of individual PAHs and mixtures of PAHs with As, Cd and Pb on 7 day aged soils and soils aged up to 90 days were investigated using UBM and HepG2 cells in vitro methods.…”

“…Moreover, the results in this chapter suggest that a major route of PAH uptake in HepG2 cells is passive diffusion. In a previous study, Vasiluk et al (2007) It is generally believed that hydrophobicity might play a role in bioavailability of PAHs. Gilbert et al (2014) has reported diffusive transport is particularly relevant for the transport of highly hydrophobic chemicals (log Kow > 5).…”

“…The use or absence of food component is referred to as the "fed" or the "fasted" state. Bioaccessibility of a PAHs can also be influenced by a number of soil properties such as total organic carbon (Hack and Selenka, 1996;Vasiluk et al, 2007), silt and clay (Meyer et al, 2015;Duan et al, 2014) and black carbon (Meyer et al, 2015). Further, the effect of ageing and weathering of soils is also reported to influence PAH absorption, hence bioaccessibility (Ruby et al, 2016).…”