Validation of the In Vitro Gastrointestinal (IVG) Method to Estimate Relative Bioavailable Lead in Contaminated Soils

Abstract

The effect of the dosing vehicle (e.g., dough) on the ability of an in vitro gastrointestinal (IVG) method to predict relative bioavailable Pb associated with soil ingestion was evaluated. Bioaccessible Pb determined by the IVG method was compared with relative bioavailable Pb measured from dosing trials using juvenile swine for 18 contaminated soils ranging from 1270 to 14200 mg Pb kg(-1). Bioaccessible Pb was measured in the IVG gastric extraction (GE) and intestinal extraction (IE) solutions. Mean bioaccessible Pb values were 32.2% for GE without dough, 23.0% for GE with dough, 1.06% for IE without dough, and 0.56% for IE with dough. It is possible that phytic acid associated with the dough addition decreased bioaccessible Pb. In vivo relative bioavailable Pb ranges for different swine tissues were 1 to 87% for blood, 0 to 110% for liver, 1 to 124% for kidney, and 0.04 to 94% for bone. Strong linear relationships between IVG GE Pb with dough (r > 0.76, P < 0.0002), IVG IE Pb with dough (r > 0.56, P < 0.015), and IVG GE Pb without dough (r > 0.81, P < 0.0001) and in vivo bioavailable Pb as estimated with blood, kidney, liver, and bone were found. Inexpensive in vitro methods may be useful in providing an estimate of the variability in relative bioavailable Pb at a single study site. The IVG method can be used to estimate relative bioavailable Pb, As, and Cd in contaminated soil.

Bioaccessibility of Pb from Ammunition in Game Meat Is Affected by Cooking Treatment

“…After cooking, whole Pb shot pellets were removed from each breast, as is normal when eating game, since the consumer will commonly detect and remove whole shot while masticating. The meat was then finely minced (simulating mastication) and processed to simulate human digestion following a previously described in vitro procedure [16], with some modifications based on other models [15], [17], [20].…”

“…This was composed of porcine bile extract (0.14 g/ml; Sigma) and pancreatin (0.014 g/ml; Sigma). The final concentration of these reagents in each tube was 3.5 mg/ml and 0.35 mg/ml respectively [16]. The pH was then adjusted to 6.5 with a saturated NaHCO 3 solution.…”

“…In order to utilise the model, we first had to transform our observed bioaccessibility data into bioavailability values as follows. In vitro and in vivo Pb bioaccessibility or bioavailability (for contaminated soil) are sometimes expressed in relative terms, i.e., with respect to values obtained for a reference material/dietary source such as Pb acetate [14], [16], [18]. The solubility of Pb acetate at an intestinal pH of 6.5 has been previously calculated as 14.3% [18].…”

Mineralogy affects geoavailability, bioaccessibility and bioavailability of zinc

“…Thus, simpler in vitro bioaccessibility tests to estimate bioavailability would be valuable. Several studies have estimated oral bioavailability of metals in contaminated soils and mine wastes using in vitro tests with a single extraction or series of extractions designed to mimic the GI system (Bradham et al, 2011; Casteel et al, 2006; Juhasz et al, 2009a; Juhasz et al, 2009b; Navarro et al, 2006; Ruby et al, 1996; Schroder et al, 2004). These studies concluded that the characteristics of each metal (Navarro et al, 2006), pH of the extraction solution (Juhasz et al, 2009a; Juhasz et al, 2009b; Ruby et al, 1996), mineralogical composition of samples (Bradham et al, 2011; Navarro et al, 2006), matrix properties and presence of other organic or inorganic components (Casteel et al, 2006) significantly influenced bioaccessibility.…”

“…Studies of Pb- and As-contaminated soils showed that in vitro extraction results successfully predicted Pb bioavailability in rats, but over-predicted As bioavailability in rabbits and primates (Ruby et al, 1996). Bioaccessibility of Cd in contaminated soils extracted in simulated gastric or intestinal fluids was significantly correlated with relative bioavailable Cd in swine (Schroder et al, 2004). …”