Oral Bioavailability - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 311

statistical modelling of geochemical soil survey data) was used. The findings
showed that the bioaccessible arsenic was generally less than and mainly contained
within calcium iron carbonate (sideritic) assemblages and only partially iron alumi-
nosilicates, probably berthierine, and iron oxyhydroxide phases, probably goethite.
The bulk of the non-bioaccessible arsenic was bound up with less reactive iron oxide
phases.
Naturally occurring arsenic in soils (13-384 mg kg -1 ) at a new housing site in
southwest England (Nathanail and Smith 2007 ) were demonstrated not to pose unac-
ceptable risk to human health by site specific estimates of bioavailability and region
specific estimates of soil to plant uptake factors. Independent lines of evidence,
consisting of data from sequential extraction of representative test soils and soil to
plant uptake factors for the site were used to justify the arsenic exposure factors
for oral bioavailability. The results of the study and subsequent Risk Assessment
avoided the need for remediation and unnecessary public concern.
Denys et al. ( 2007 ) studied the bioaccessibility of lead in soils with a high
lead carbonate (cerrusite) content (up to 870 g kg − 1 ). The authors found that lead
bioaccessibility, using the RIVM in-vitro protocol, in high carbonate soils can be
low (down to 20% of the total soil Pb content) and is not correlated with cerus-
site soil contents even if the concentration of this mineral is relatively high. This
research indicates that mineralogical analysis alone is not a reliable predictor of the
bioaccessible fraction.

7.4.2 Anthropogenic Influences

Basta and co-workers have investigated the bioaccessibility of arsenic and lead,
using the in-vitro gastro intestinal method (IVG) in smelter impacted soils over a
number of years (Basta et al. 2007 ; Rodriguez et al. 1999 ). Method development
of the IVG included validation and dosing trials of immature swine for fifteen soils
ranging in total arsenic concentrations of 401-17,460 mg As kg − 1 . The research
indicates that IVG methodology was linearly correlated with the animal model
( r 0.83, p <0.01) for arsenic relative bioavailability ranging from 2.7 to 42.8%

(Rodriguez et al. 1999 ). Further research by this group investigated the effect of
the dosing vehicle used to determine the bioaccessibility, using the same contam-
inated materials as employed in the 1999 research (Basta et al. 2007 ). Similarly
to previous research, the IVG was shown to produce strong relationships with the
in-vivo arsenic bioavailability, with or without the presence of a dosing vehicle
( r

=

0.96 (without) p < 0.01). Further to the work
on arsenic, the applicability of the IVG methodology has been investigated for
soils contaminated with cadmium (Schroder et al. 2003 ). Relative bioavailable cad-
mium for ten soils (containing total cadmium ranging between 23.8 and 465 mg
kg − 1 ) was obtained from dosing trials using juvenile swine and ranged from 10.4
to 116%. Linear regression with cadmium bioaccessibility from the IVG method-
ology indicated strong correlations with both the stomach ( r

= 0.92 (with), p < 0.01) and r =

= 0.86) and intestinal

( r = 0.80) phases of the IVG.