Oral Bioavailability - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 315

examine the variability amongst individual methods and by comparison of results to
toxicological reference values (BARC 2008 ).

7.5.2 Utilization of Bioaccessibility Data Across Europe

The utilization of the concept of oral bioavailability/bioaccessibility is used in a
highly variable manner across Europe. In France, until recently, bioaccessibility was
not taken into account in Human Health Risk Assessment. However, more recently,
the Institut National de l'Environnement Industriel et des Risques (INERIS) has
been tasked with the development of research programs that include the application
of bioaccessibility testing in Human Health Risk Assessment and assessing the ben-
efits of the inclusion of such testing regimes. As a part of its risk based approach to
the management of contaminated land there is guidance is in place in the UK that
recognises the potential benefits of, and allows for the inclusion of, oral bioavail-
ability/bioaccessibility data in Human Health Risk Assessments when addressing
exposure to significant possibilities of significant harm (SPOSH) (Department for
the Environment Food and Rural Affairs and the Environment Agency 2002 ; ODPM
2004 ). Similarly, in Canada, although absorption factors for ingestion are usually
100% in screening level Risk Assessments, oral bioavailability is often determined
as bioaccessibility, and for complex Risk Assessments site specific bioaccessibility
values may be determined as a surrogate of bioavailability (Health Canada 2004 ).
However, currently there is a paucity of guidance available concerning the appli-
cation of bioaccessibility data in UK and Canadian Risk Assessments, which has
lead to a degree of uncertainty within the practitioner community regarding the use
of this potentially beneficial tool. In the US, the 'Risk Assessment Guidance for
Superfund, Volume 1' (USEPA 1989) considers the determination of bioavailabil-
ity on a site-specific basis, and more recently guidance has become available for
a number of issues surrounding site-specific bioavailability data (USEPA 2007a).
Such issues include:

• implementation of a validated methodology, and documentation of data collec-

tion and analysis;

•

EPA criteria for the evaluation of a bioavailability methodology, to test its
suitability for use.

Additionally, after recent validation of an in-vitro methodology for lead against
in-vivo swine data, there is growing support for the use of reliable bioaccessibility
data, in the first instance for Pb in Human Health Risk Assessments (USEPA 2007b).
Despite apparent confusion surrounding the science and application of bioacces-
sibility testing within the UK contaminated site community, process understanding
of the mechanisms controlling bioaccessibility has continued with respect to priority
UK contaminants (arsenic, chromium, nickel, lead and poly aromatic hydrocarbons
(PAHs)), in addition to the application of bioaccessibility data in site-specific UK
detailed quantitative Risk Assessments. Research on bioaccessibility testing has