Comparison of Five In Vitro Digestion Models To Study the Bioaccessibility of Soil Contaminants

Abstract

Soil ingestion can be a major exposure route for humans to many immobile soil contaminants. Exposure to soil contaminants can be overestimated if oral bioavailability is not taken into account. Several in vitro digestion models simulating the human gastrointestinal tract have been developed to assess mobilization of contaminants from soil during digestion, i.e., bioaccessibility. Bioaccessibility is a crucial step in controlling the oral bioavailability for soil contaminants. To what extent in vitro determination of bioaccessibility is method dependent has, until now, not been studied. This paper describes a multi-laboratory comparison and evaluation of five in vitro digestion models. Their experimental design and the results of a round robin evaluation of three soils, each contaminated with arsenic, cadmium, and lead, are presented and discussed. A wide range of bioaccessibility values were found for the three soils: for As 6-95%, 1-19%, and 10-59%; for Cd 7-92%, 5-92%, and 6-99%; and for Pb 4-91%, 1-56%, and 3-90%. Bioaccessibility in many cases is less than 50%, indicating that a reduction of bioavailability can have implications for health risk assessment. Although the experimental designs of the different digestion systems are distinct, the main differences in test results of bioaccessibility can be explained on the basis of the applied gastric pH. High values are typically observed for a simple gastric method, which measures bioaccessibility in the gastric compartment at low pHs of 1.5. Other methods that also apply a low gastric pH, and include intestinal conditions, produce lower bioaccessibility values. The lowest bioaccessibility values are observed for a gastrointestinal method which employs a high gastric pH of 4.0.

Health risks from the exposure of children to As, Se, Pb and other heavy metals near the largest coking plant in China

“…Using bioavailable or bioaccessible elements concentrations (Brown et al, 1999) to conduct human non-carcinogenic and carcinogenic risk evaluations is considered to be the most reliable and accurate method (Oomen et al, 2002). However, animal experiments to quantify the bioavailable element concentrations and estimate the human health risk usually are costly and could suffer from ethical concerns, whereas in vitro digestion models are not suitable for estimating both the dermal contact and inhalation exposure.…”

Lead bioaccessibility in 12 contaminated soils from China: Correlation to lead relative bioavailability and lead in different fractions

“…method (DIN), and unified BARGE method(UBM) [17][18][19][20][21]. However, due to variation in gastrointestinal fluid components and assay parameters (e.g., pH, soil/solution ratio, and extraction time), different assays often producedifferentbioaccessibility results [10,15,22]. Therefore, before these assays can be used to accurately predict Pb-RBAin contaminated soils, they need to be correlated toPb-RBA determined via animal models.…”

Heavy Metal Bioavailability and Bioaccessibility in Soil

“…Several distinct approaches for performing in vitro gastrointestinal extraction are available (7,8); however, two are considered in this chapter.…”