Site-Specific Ecological Risk Assessment - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 703

respective tools in comparative cases. If not, this should be specifically addressed.
This is often the case with tools used in higher tier Risk Assessment, because of
insufficient scientific foundation.
As a rule of thumb, simple, common, standardized and low-cost tests should be
used in the lower tiers of the ERA, whereas more laborious and sophisticated tests
should be applied in the higher tiers. Guidance for selecting appropriate tools is
available (e.g. Fairbrother et al. 2002 ; Jensen and Mesman 2006 ; Römbke et al.
2006a ; Rutgers et al. 2008a ). The highest level of protocol standardization of tests
is reached in international guideline programs such as ISO and OECD. Whereas the
OECD test program has focused on tests suitable for the evaluation of chemicals,
the ISO guideline program has, at least recently, focused on test systems for the
evaluation of the risks of contaminated soil (Römbke et al. 2006b ). Additional pro-
tocol standardization comes from quality assurance systems like Good Laboratory
Practice (GLP). Methods described in the scientific literature can also be used, espe-
cially in the higher tiers of ERA. In any case, it may frequently be necessary to adopt
the tests to site-specific conditions. The number of laboratories able to perform a
specific test on a routine or semi-routine basis is another issue when selecting the set
of tools. Finally, the acceptance of the tests by the stakeholders, risk assessors and
the scientific community plays a role in the selection criteria. Last but not least, it is
important to minimize the bias caused by the risk assessor's background. It is, for
example, a human commonality to overstress the importance of the own expertise
in solving complex problems. With large multidisciplinary research teams, however,
this problem is somewhat reduced.
The combination of different tools from different disciplines at different levels
of standardization, robustness, sensitivity and ecological relevance without being
able to fit them all in one comprehensive and accepted ecosystem theory is in fact
a matter of combining 'apples and oranges'. This highlights the need for a proper
multi-criteria decision analysis (MCDA) in ERA (Chapman et al. 2002 ;Linkov
et al. 2006 ). With MCDA it is possible to combine different pieces of not a-priory
related information in an unconstrained way. It opens the possibility to cope with
divergent, but best professional judgments from separate experts in a transparent
framework process.
15.4.3 Quantification and Scaling
Essentially, the results from all tools to be applied, including bioassays and eco-
logical field surveys, should be funneled into the ERA. Key for efficient use of
information is 'scaling'; i.e. the projection of results from different tools on a com-
mon and unified 'effect scale' (e.g. inhibition of growth, or loss of reproduction
should be both expressed in the comparable units as an ecological effect). The pri-
mary aim is to maximize the utilization of individual results, and to use results
from all tests together in transparent and integrative schemes, for example in a deci-
sion matrix. Burton et al. ( 2002a, b ) reviewed several possibilities for disseminating