Introduction to Contaminated Site Management - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 33

body) or target organs (in case of local effects, i.e., related to effects to specific
organs at the place of contact or intake) is determined. This amount is expressed as
mass contaminant, per body weight mass, per unit of time (mg/kg body weight /day),
that is, as the internal exposure. Target organs are the organs that could be adversely
affected by specific contaminants. However, in most cases the external exposure is
calculated, that is, the amount of a contaminant that reaches the human body or the
organism.
With regard to the determination of human exposure, multimedia calculations
are usually combined with the calculation of human exposure in so-called exposure
models. A more detailed introduction to Human Health Risk Assessment is given
in Swartjes and Cornelis ( Chapter 5 of this topic). A quantitative determination of
human exposure is described in detail in Chapters 7 , 8 , 9 , 10 , and 11 of this topic.
An important first step in Exposure Assessment is to determine the representative
soil concentration . The representative soil concentration, and hence, the proce-
dure for soil and groundwater sampling, is dependent on the purpose of the Risk
Assessment, the site characteristics and the exposure pathways that are the most
relevant. Smart choices need to be made for location and depth of the samples, con-
struction of the composite samples, and contaminants that must be analysed (see
Section 1.4 ). A site visit and historical survey can be important activities in support
of the chosen sampling strategy.
Hazard Assessment includes two steps, namely, Hazard Identification and
Hazard Characterisation (IPCS 2004 ). Hazard Identification focuses on the pos-
sible effects of specific contaminants and the time frame for which these effects
occur. Subsequently, the Hazard Characterisation results in a dose-response assess-
ment, relating exposure to effects, and is the basis for the determination of Critical
Exposure (aka: Reference Dose).
The combination of Exposure Assessment and Hazard Assessment, the second
step of the Risk Assessment framework, is called Risk Characterisation . When
translated in objective terms, the Risk Characterisation results in a Risk Index .
This is the ratio between actual exposure and Critical Exposure with regard to
Human Health Risk Assessment, or the ratio between the actual concentration and
acceptable concentration in the soil with regard to Ecological Risk Assessment,
respectively. In Ecological Risk Assessments often the PEC/NEC (Predicted Effect
Concentration/No Effect Concentration) ratio is used for one organism, several
organisms or the whole ecosystem, with the same goal in mind. Dawson et al.
( 2007 ), as another example, established a Biological Soil Quality Index to help
visualize significant differences in hydrocarbon-polluted soils.
The actual performance of Risk Assessment is generally supported by appropri-
ate Risk Assessment tools . In Swartjes et al. ( 2009 ) a Risk Assessment tool is defined
as any instrument that can contribute to the determination of risks at a contami-
nated site. A Risk Assessment tool can be an equation, a description, a database,
a model, an instrument, a protocol, or a table. A combination of selected Risk
Assessment tools is called a Toolbox . Such a Toolbox does not include policy points
of view. The Toolbox for the determination of human health risks, for example, may
include algorithms for the calculation of exposure through different pathways, a
measurement protocol for the determination of the indoor air concentration, a table