Assessment of Persistent Organic Pollutant (POP) Bioavailability and Bioaccessibility for Human Health Exposure Assessment: A Critical Review

Abstract

Persistent organic pollutants (POPs) are ubiquitous environmental contaminants which persist in the environment, bioaccumulate through the food chain, and pose a risk of causing adverse effects to human health and the environment. When quantifying exposure to POPs via incidental soil ingestion for human health risk assessment, it is assumed that 100% of the contaminant is bioavailable for absorption into systemic circulation. However, this assumption may overestimate exposure thereby influencing risk calculations. A variety of in vivo and in vitro methods have been developed in order to quantify POP bioavailability for exposure assessment. The authors review bioavailability assays utilizing animal models (in vivo), surrogate assays (in vitro) for estimating in vivo POP bioavailability, the validation of surrogate assays, and future research needs for POP bioavailability determination.

KEY WORDS:

• bioaccessibility
• bioavailability
• in vitro
• in vivo
• persistent organic pollutant

Notes

^aSolubility determined at 25°C.

^bSolubility determined at 20°C.

^cVapor pressure determined at 20°C.

^dVapor pressure determined at 25°C.

^eTetrachlorodibenzo-p-dioxin.

^aThe TIM bioaccessibility method developed by Minekus et al. (1995) is a dynamic system.

^bThe in vitro method consisted of 9 ml of esophageal phase, 13.5 ml of gastric juice, 27 ml of duodenal juice and 9 ml of bile solution.

^cThe in vitro method consisted of 20 ml of esophageal phase, 40 ml of gastric juice, 40 ml of duodenal juice and 20 ml of bile solution.

^dInformation in parentheses indicates the mode of pH adjustment.

^aInformation in parenthesis indicates method of pH adjustment.

^bInformation in parenthesis indicates method of pH adjustment.

^cMixed bile salts were added at 0.1, 5.0 and 20 mM to represent fasting, fasting with gall bladder emptying, and fat digestion states.

^dMixed intestinal lipids were only added during the fat digestion state.

^eThe duodenum digest suspension (100 ml) was supplemented with 100 ml of SHIME suspension (Simon and Gorbach, 1995). SHIME contained microbiota representative of the composition and concentration in the human colon. Lactobacilli, Bifidobacteria, Enterococci, Fungi, Staphylococci, and Clostridia were included with total anaerobic and aerobic microorganisms at approximately 8.4 and 7.8 log colony forming units (CFU) ml⁻¹. The colon digest was incubated at 37°C and stirred at 150 rpm for 18 h.

^aSee Tables 5 and 6 for a description of the in vitro bioaccessibility method employed.