Mobility of Polycyclic Aromatic Hydrocarbons in the Gastrointestinal Tract Assessed Using an in Vitro Digestion Model with Sorption Rectification

Abstract

In a previous study, it was demonstrated that mobilization of organochlorine pesticides would be underestimated by an in vitro gastrointestinal model if the sorption of the mobilized pollutants on the digestive residue was not taken into consideration. A multiple fluid/solid ratio procedure was developed to characterize the sorption. In this study, the sorption hypothesis was further tested for polycyclic aromatic hydrocarbons (PAHs), and the sorption of the mobilized PAHs on digestive residue was directly characterized by spiking the gastrointestinal digest with several deuterated PAHs. It was demonstrated that 10-41% of the spiked deuterated PAHs were sorbed on the assimilated residue, which would remain in the solid phase after separation. It appears that the mobility of PAHs would be underestimated if only those dissolved in the fluid is measured. The total mobilized fraction of a PAH compound was defined as a sum of that dissolved in the fluid and that sorbed on the residue. The average mobilized PAH fractions in the studied soils was 70 +/- 24% which was significantly higher than 47 +/- 19% in the fluid. It was also found that the sorption of the mobilized PAHs on the digestive residue was positively correlated with both soil organic carbon (SOC) and molecular weight (MW(t)) of PAHs, and a regression model was developed so that the sorption of different PAHs on soils with different SOCs could be estimated.

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

“…Previous studies on bioaccessibility of PAH in PBET models and on PAH desorption in the water-solid system (Hawthorne et al 2002) suggested decreasing bioaccessibility with increasing ring number, molecular weight, or log K ow of PAH (Cave et al 2010;Khan et al 2008;Tang et al 2006;Tao et al 2010). In this study, no negative correlation of PAH bioaccessibility with increasing molecular weight or log K ow was observed.…”

“…With regard to the behavior of single PAH, it is mostly concluded that PAH bioaccessibility decreases with increasing molecular weight (Cave et al 2010;Khan et al 2008;Tang et al 2006;Tao et al 2010) which implies increasing sorption tendency expressed by an increasing octanol-water partition coefficient (log K ow ).…”

“…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

“…In published literature, bioaccessibility of up to 20 % of total PAHs has been reported for fasted in vitro gastrointestinal tests similar to UBM (Tilston et al, 2011;Cave et al, 2010;Tao et al, 2010;Gron et al, 2007;DIN, 2000). 143 As a conservative measure of bioaccessibility assessment in static systems such as UBM, recent studies have investigated the role of sorption sinks using materials such as Tenax and silicone cord to improve the mass transfer of PAHs into gastrointestinal solutions, these materials prevented readsorption of PAHs to soil and hence bioaccessibility of total PAHs increased from 8.25 -20.8 % (without Tenax) to 55.7 -65.9% (using Tenax) and up to 81.7 ± 2.7 % using silicone cord Juhasz et al, 2016).…”

“…In general, a number of bioaccessibility tests for PAHs have been reported. Both batch (Tilston et al, 2011;Cave et al, 2010;Tao et al, 2010;Gron et al, 2007;DIN, 2000) and dynamic model (Van de Wiele et al, 2004) have been used, but most studies simulate the human stomach and upper intestine (Cave et al, 2010;Gron et al, 2007;DIN, 2000) and the colon compartment (Tilston et al, 2011;Van de Wiele et al, 2004) in bioaccessibility assessment. Notably, some bioaccessibility tests include a food component (Cave et al, 2010;DIN, 2000;Gron et al, 2007) such as lipids due to their effect on the extraction of PAHs (Harris et al, 2013).…”