Human Exposure Pathways - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 483

• Some exposure parameters are poorly known, such as the quantities of soil

ingested by animals. Depending on the conditions in which the animals are
reared, this parameter can vary substantially (for example, there are differences
between soil with a dense cover of grass versus bare ground, and between graz-
ing animals versus confined animals). Exposure data should be adapted to the site
under consideration, but reliable reference data are rather scarce, especially for
soil ingestion.

Finally, There are uncertainties involved in the calculation of human exposure.
They are due to the fact that humans eat different products, which are merged
into a few categories, which are more or less representative of the actual con-
sumption and which are assumed to have a single contaminant concentration.
Besides, the impact of food preparation on the concentration in animal prod-
ucts is not taken into account. Another factor concerns inter-individual differences
between humans. Some individuals consume more animal products concentrat-
ing high levels of contaminants (such as offal) than the average population. If
such subpopulations are present on the site, their specific exposure should be
considered.

11.4 Exposure Via Domestic Water

Groundwater used as domestic water can be contaminated through leaching of con-
taminants from the soil and subsequent transport to the groundwater. The process of
groundwater contamination is very site-specific and is often treated in a simplified
manner in Risk Assessment models, e.g., the models used for Soil Quality Standards
in USA, Sweden and Flanders. The contaminant concentration in the groundwater
is usually calculated based on dilution of the soil pore water in the groundwater,
neglecting the temporal evolution of the contaminant plume. See Chapter 19 by
Rolle et al., this topic. In many countries Soil Quality Standards do not consider
groundwater as a protection target for contaminants from the upper soil layers, e.g.,
the Netherlands and Denmark. Instead separate standards are developed for ground-
water quality based on the use of groundwater for domestic purposes and ecological
effects in the groundwater.
Domestic water can also be contaminated due to permeation of organic contam-
inants through plastic water pipes placed in contaminated soil. For example, this
pathway is included in the Dutch CSOIL model (Brand et al. 2007 ; Van den Berg
1991 / 1994 / 1995 ) and the Flemish Vlier-Humaan model (OVAM 2004 ). Surface
water may also be used as a source for domestic water. However, this pathway
is rarely considered in Risk Assessment models for contaminated soils, since the
groundwater pathway usually gives higher exposure than the surface water pathway,
due to less dilution.
This section will only deal with methods used to estimate the exposure due
to use of contaminated domestic water, not how the domestic water has been
contaminated.