Environmental Engineering Reference
In-Depth Information
Figure 11.13 Alternatives between no observed effect concentration (NOEC) and lowest observed
effect concentration (LOEC) on the concentration-response curve.
and a laboratory which is accredited. But to reduce uncertainties, the concept of
the compilation of the best fitting tool battery is also necessary, which considers
the aim of the assessment, the nature of the contaminant and the environment.
There is no scientific consensus in this field and the available decision support is
also poor;
- Method uncertainty (measurement errors), its distance from reality (validity of the
model) and the type of extrapolation are combined in extrapolation uncertainty .
Extrapolation uncertainty should be considered when using read-across for similar
substances, applying mathematical models, such as quantitative structure-activity
relationships (QSARs), and chemical, biological or microcosm models. Applying
probability-based extrapolation gives a result closer to the real environment than
extrapolation based on the use of assessment factors. Extrapolation in the field of
exposure assessment mainly covers transport and fate modeling and mapping. The
following extrapolations are used in hazard assessment: interspecies, intraspecies,
acute to chronic, route to route and laboratory to field.
Figure 11.14 shows that a model does not provide an exact representation of the
real environment. A chemistry-based model can hardly represent a complex ecological
system: the picture drawn by the chemistry-based model has a different shape on the
scheme. The microcosm model gives a shape similar to the real environment. Both
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