Environmental Engineering Reference
In-Depth Information
In summary, Biomonitoring can be very supportive for site-specific Risk
Assessment, mostly in higher tier Human Health Risk Assessment and, gener-
ally, for large-scale contamination, since the costs involved are relatively high.
However, as mentioned above, these measurements also have some drawbacks. In
Section
1.7.3
, a more general viewpoint on the benefits and disadvantages of mea-
surements is given. It was concluded that the ideal Human Health Risk Assessment
is based on a smart combination of calculations (less accurate, but more representa-
tive for the long term) and measurements (more reliable, but mainly representative
for the short term).
5.3.3 Exposure Calculations
5.3.3.1 Exposure Models
A very useful and practical methodological possibility for assessing human expo-
sure is that of
calculating
human exposure, using a so-called
exposure model
. These
exposure models enable the calculation of the rate of soil contaminants that enter the
human body, blood stream, or target organs. Exposure models consider direct con-
tact with the soil and intake of so-called contact media that include contaminants
from the soil. Contact media are environmental compartments, which are in direct
contact with the soil and to which soil contaminants can migrate, such as vegetables,
indoor air and house dust.
Most of the existing exposure models use a representative
total soil concen-
tration
as a starting-point. Depending on the purpose of the Human Health Risk
Assessment, this representative soil concentration could be a relatively high esti-
mate of actual concentration (e.g., in a first tier Human Health Risk Assessment) or
an average soil concentration.
In Fig.
5.2
, the layout of the Dutch exposure model CSOIL (Brand et al.
2007
; Van den Berg 1991/1994/1995) is given, as an example. Three elements are
recognized in exposure models (see Fig.
5.2
):
•
The determination of the contaminant distribution over the soil compartments,
that is, the solid phase, pore water and soil air.
•
The determination of contaminant transfer from (the different mobile compart-
ments of) the soil into contact media (
intercompartimental relationships
).
•
The calculation of (direct and indirect) exposure of humans.
Similar often cited exposure models are CalTOX from the USA (McKone
1993
),
CLEA from the UK (DEFRA and EA 2002) and VlierHumaan from Flanders,
Belgium (Provoost et al.
2004a
).
Current Risk Assessment models generally limit exposure calculations to the
calculation of relevant concentrations, for example, in indoor air, or to
external
exposure. For the majority of soil contaminants, Toxicological Reference Values
exist for these exposure metrics, and Risk Characterisation is thus possible.
Search WWH ::
Custom Search