Polycyclic aromatic hydrocarbon release from a soil matrix in the in vitro gastrointestinal tract.
Soil ingestion is an important exposure route by which immobile soil contaminants enter the human body. We assessed polycyclic aromatic hydrocarbon (PAH) release from a contaminated soil, containing 49 mg PAH kg(-1), using a SHIME (Simulator of the Human Intestinal Microbial Ecosystem) reactor comprising the stomach, duodenal, and colon compartments. Polycyclic aromatic hydrocarbon release was defined as that fraction remaining in the digest supernatant after centrifugation for 5 min at 1500 x g. The PAH release in the stomach digest was only 0.44% of the total PAH present in soil, resulting in PAH concentrations of 23 micrograms PAH L(-1) chyme. The lower PAH releases in duodenum (0.13%) and colon (0.30%) digests, compared with the stomach digest, were thought to be attributed to combined complexation and precipitation with bile salts, dissolved organic matter, or colon microbiota. We studied these complexation processes in an intestinal suspension more in depth by preparing mixtures of 9-anthracenepropionic acid, a Bacillus subtilis culture, and cholin as model compounds for PAHs, organic matter, and bile salts, respectively. Bile salts or organic matter in the aqueous phase initially enhance PAH desorption from soil. However, desorbed PAHs may form large aggregates with bile and organic matter, lowering the freely dissolved PAH fraction in the supernatant. Using the model compounds, mathematical equations were developed and validated to predict PAH complexation processes in the gastrointestinal tract. Contaminant release and subsequent complexation in the gut is an important prerequisite to intestinal absorption and thus bioavailability of that contaminant. The data from this research may help in understanding the processes to which PAHs are subjected in the gastrointestinal tract, before intestinal absorption.
Van de Wiele
Tom Richard
TR
Laboratory Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, B-9000 Ghent, Belgium.
Verstraete
Willy
W
Siciliano
Steven Douglas
SD
D000042:Absorption; D001412:Bacillus subtilis; D001682:Biological Availability; D019149:Bioreactors; D003106:Colon / Q000737:chemistry / Q000502:physiology; D004386:Duodenum / Q000737:chemistry / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D008954:Models, Biological; D011084:Polycyclic Aromatic Hydrocarbons / Q000493:pharmacokinetics*; D012989:Soil Pollutants / Q000493:pharmacokinetics*; D013270:Stomach / Q000737:chemistry / Q000502:physiology
D011084:Polycyclic Aromatic Hydrocarbons; D012989:Soil Pollutants