PARENT SESSION
PS19 - Bioavailability
Sunday, 17 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P183) Mobilization processes of soil-bound PAHs in the gastrointestinal tract.
Van de Wiele, Tom*,1, Verstraete, Willy1, Siciliano, Steven1, 1 Laboratory Microbial Ecology and Technology, Ghent University, Ghent, Oost-Vlaanderen, Belgium
ABSTRACT- Site-specific risk assessments incorporate soil ingestion as an important exposure route to the human body for environmental contaminants. To assess the risk for intestinal uptake of soil-bound polyaromatic hydrocarbons (PAHs), more information is required on the release mechanisms that influence PAH mobilization along the gastrointestinal tract. We assessed PAH release from a soil matrix using a SHIME reactor (Simulator of the Human Intestinal Microbial Ecosystem). A contaminated soil (49 mg PAH/kg DW) from a recreation area was digested according to a stomach, duodenal and colon model. Pellet and supernatant of the suspensions were analyzed for PAHs with GC-MS, yielding a 92, 89 and 97 % mass recovery for stomach, duodenal and colon digests, respectively. Soil organic matter, contaminant hydrophobicity, stomach pH, enzymatic or biliary secretions and presence of microbial biomass, were investigated for their influence on PAH mobilization. PAH release, observed for the stomach digestion was 0.46 %, where pH influence was of minor importance. Presence of food components gave rise to a higher release, 1.41 %, in the stomach model, due to an increased number of hydrophobic sorption sites in the aqueous phase. Lower PAH concentrations in the supernatant from duodenum (0.16 %) and colon (0.22 %) digests could be attributed to complexation with bile salts, dissolved organic matter or colon microbiota. Microscopic analysis of a mixture of bile salts, particulate organic matter and a fluorescent PAH derivative confirmed these observations. The presence of bile salts or organic matter in the aqueous phase enhanced the PAH release from the soil, but large aggregates with bile and organic matter lowered the readily absorbable fraction of the mobilized PAHs. These data demonstrate that several processes are involved in PAH mobilization from soil along the gastrointestinal tract.
Key words: Bioavailability, ingestion, PAH, soil