Development and Validation of the Unified Barge Bioaccessibility Method for As, Cd and Pb In Soils.

 

The Bioaccessibility Research Group of Europe (BARGE) is a European network bringing together international institutes to study human bioaccessibility of priority contaminants in soils e.g. (As), lead (Pb) and cadmium (Cd) via the gastrointestinal (GI) tract.  A primary objective is to provide robust and defensible bioaccessibility data for human health risk assessments and policy making. Variable results from method comparison studies have hindered the adoption of bioaccessibility methods by some in the regulatory community. BARGE initiated the development of a harmonised in vitro bioaccessibility test: the Unified BARGE Method (UBM).

 

An International inter-laboratory trial determined the repeatability and reproducibility of results within and between testing laboratories.  Seven laboratories participated, extracting 34 contaminated samples (soils, mine wastes and slag materials).  The UBM met the stated benchmark criteria for in vivo validation (a vivo/vitro linear relationship, a very strong correlation coefficient (r >0.8 or r2 >0.6) and a slope >0.8 and < 1.2) for both the GI phases for As and the stomach phase for Cd. 

 

In addition INERIS and the University of Nancy undertook the validation of the UBM for As, Cd and Pb using a juvenile swine model which showed very strong correlation between the relative bioavailability and bioaccessibility for As, Pb and Cd. The slopes of the regressions were all > 0.9 and <1.1 and the intercepts were not significantly different from 0. An example in vivo/in vitro correlation plots for Pb is shown in Figure 1.

 

The UBM method has been applied extensively in the UK to assess the bioaccessibility of Pb and As in urban rural and mineralised areas. Figure 2 shows the relationship between total As and bioaccessible As in London soils.

 

Figure 1 Pb Bioaccessibility /Bioavailability comparison           Figure 2 Bioaccessibility of As in London soils