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BARC (Bioaccessibility Research Canada) was established in 2005 to develop collaboration
and funding opportunities for advancing understanding of the factors influencing
soil inorganic and organic contaminant bioaccessibility and its correct measurement.
This is important because the correct estimation of bioaccessibility has the potential
to significantly impact risk assessments and cleanup goals at contaminated sites.
For most contaminants, toxicity depends on how much of the contaminant is absorbed
into the body. When the exposure route is ingestion of soil borne contaminants toxicity
depends upon absorption from the gut. Hence, information on the bioavailability of
a contaminant (how well a contaminant is absorbed from the gut) is important to determining
how much of a contaminant humans can be exposed to without posing a health risk.
Bioaccessibility is a measure of the physiological solubility of a metal in the gut.
Because solubility is usually required for absorption across membranes bioaccessibility
may be a predictor of bioavailability when solubility is the major determinant of
absorption across the gut epithelium
The exposure media (i.e. soil versus food or water) can influence the absorbance
of a contaminant and therefore accounting for potential differences in absorption
between different exposure media can be important to site risk assessment. It is
now widely accepted that contaminants in soil may be absorbed to a lesser extent
than contaminants in food or water. Hence, if the exposure media used to derive a
TRV is water or food, risks from ingestion of the contaminant in soil might be overestimated.
For sites where large volumes of soil need to be remediated even a relatively small
bioavailability adjustment can have significant impacts on estimated risks and cleanup
To advance the meaningful incorporation of bioaccessibility in HHRA risk assessment
BARC activities are focused on achieving the following research goals:
· The development of reliable and rapid bioaccessibility tests that have been validated
with in vivo studies ;
· The development of two or more Canadian reference materials with in vivo data
for ensuring the reliability and consistency of bioaccessibility test results; and
The development of standardized in vitro and in vivo protocols for ensuring the correct
application of bioaccessibility data in HHRA.
is defined as the proportion of the mass of a soil-borne contaminant reaching the
GIT that is systemically absorbed (in vivo assay), or that is deemed to be available
for systemic absorption (in vitro bioaccessibility assay).
is defined as the absolute bioavailability (or bioaccessibility) from the site-specific
soil samples divided by the absolute bioavailability of the same substance under
the conditions used to derive the toxicological reference value (TRV)