Oral Bioavailability - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 313

Since its inception, the BARGE group has been active in the field of oral
bioavailability and bioaccessibility. The activities include the undertaking of a
number of round robin studies (see section below); liaising with the International
Standards Organisation on the preparation of a technical specification entitled
'Soil quality - Assessment of human exposure from ingestion of soil and soil
material - Guidance on the application and selection of physiologically based
extraction methods for the estimation of the human bioaccessibility/bioavailability
of metals in soil'; the dissemination of findings through the development of
a website ( www.bgs.ac.uk/barge ), the hosting of workshops/dedicated speaker
sessions on bioaccessibility related topics at International conferences such as
ConSoil ( http://consoil.ufz.de /); and the preparation of a peer reviewed special
publication on bioaccessibility topics (Gron and Wragg 2007 ).
As the research on oral bioavailability, and the development of oral bioavailabil-
ity factors, is not an issue specific to Europe, and affects contaminated site practi-
tioners worldwide, the BARGE group is an ever expanding International research
network, combining the cross-continental collaborative efforts of Europe and North
America. In a similar vein to the BARGE group, researchers, Risk Assessment prac-
titioners and regulators in Canada with an interest in oral bioavailability and the
application of resulting tools have joined forces to form BioAccessibility Research
Canada (BARC). The long term aim of this group is 'to provide a scientific basis
for evaluating and predicting inorganic and organic contaminant bioaccessibility
in soils found at contaminated sites in Canada' (BARC 2006 ). To address issues
relating specifically to the measurement of arsenic oral bioavailability and bioac-
cessibility by in-vivo and in-vitro methodologies respectively, researchers from both
the BARGE and BARC groups have joined forces with other research institutes and
government bodies to share knowledge via an electronic forum.
7.5.1 Inter-Laboratory Studies
To date, four international inter-laboratory studies have been carried out to
investigate different aspects of bioaccessibility in the human gastro-intestinal tract.
Three have been undertaken by the BARGE group, two of which have been pub-
lished in peer reviewed publications (Oomen et al. 2002 ; Van de Wiele et al.
2007 ). Oomen et al. ( 2002 ) described a multi-laboratory study which compared
the bioaccessibility data returned by five in-vitro methods for three solid materials,
contaminated with arsenic, cadmium and lead. The methods included physiologi-
cally and non-physiologically based test systems of dynamic and static nature. The
salient points of the study were that, in many cases the bioaccessibility was <50%,
an important factor for Human Health Risk Assessment, although a wide range
of bioaccessibility values were observed across the in-vitro methods studied. The
primary driver for the range in bioaccessible values was attributed to the differ-
ence in gastric pH of the various test systems. High bioaccessibilities were typically
observed for the simplest method (stomach compartment only) with a low gastric pH
and the lowest values for the system with the highest gastric pH (4.0). Low bioac-
cessible values, however, were also observed with two-phase systems incorporating