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from different disciplines, rather than from one set of tools in one discipline. This
makes the Triad approach a scientifically sound and practical instrument, during
different stages of ERA.
15.4 Practical Issues for Adoption of the Triad Approach
15.4.1 Uncertainty
Uncertainty is a key element in Risk Assessment and should be properly addressed
and communicated. Uncertainty can be seen as the state of imperfection within the
total available amount of information with respect to the environmental problem and
the requested decision to be made in time (Walker et al. 2003 ). Uncertainty contains
both subjective and objective elements. The subjectivity originates from the judg-
ment about the validity and appropriateness of the information. Objectivity comes
from the data and facts related to the contaminated site. Uncertainty is therefore
often separated in:
Variability and error, i.e. lacking or imperfect data and data from systemic vari-
ations in space and time. An example is the variation in results by application
of a specific tool: in one assay with real replicates, with pseudo replicates, from
inter-laboratory variation, and through gradients in space or time.
Incertitude, i.e. model imperfections; or in more popular terms: you do not know
what you do not know. This uncertainty is demonstrated by application of dif-
ferent tools at one occasion (sample or site), both within a line of evidence, or
between different lines of evidence.
It is important to realize that both types of uncertainty need appropriate, but
inherently different approaches in the Risk Assessment. Recently, linguistic uncer-
tainty was introduced additionally to these two types of uncertainty (Carey and
Burgman 2008 ;Levin 2006 ). Linguistic or language related uncertainty between
risk assessors and risk managers may arise especially in the case of ERA, because
of a lack of appropriate terms and definitions, imprecise problem framing and dif-
ferent perspectives and views on the environment (Kellett et al. 2007 ). A clear and
transparent communication between stakeholders before, during and after the exe-
cution of an ERA is therefore crucial: it is the only way to minimize the chance on
misperceptions.
It is beyond the scope of this chapter to recapitulate all aspects of uncertainty.
Instead references are made to the respective literature, (e.g. Beer 2006 ;Burton
et al. 2002a , 2002b ;Levin 2006 ; Nayak and Kundu 2001 ;Walkeretal. 2003 ). As an
idea we state that variability and error are primarily solved by increasing the amount
of effort, e.g. via more samples, more replicates, and further optimizing the noise to
signal ratio via improving of assessment tools. Weight of evidence approaches like
the Triad seems to be preferred in order to reduce uncertainty caused by incertitude
(including ignorance and indeterminacy).
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