Environmental risk assessment of chemical substances in the European Union is based on a harmonised scheme. The required models and parameters are
laid down in the Technical Guidance Document (TGD) and are implemented in the EUSES software. An evaluation study of the TGD exposure models was
carried out. In particular, the models for estimating chemical intake by humans were investigated. The objective of this study was two-fold: firstly, to
develop an evaluation methodology, since no appropriate approach is available in the scientific literature. Secondly, to elaborate applicability and limitations
of the models and to provide proposals for their improvement.
The principles of model evaluation in terms of quality assurance, model validation and software evaluation were elaborated and a suitable evaluation protocol
for chemical risk assessment models was developed. Quality assurance of a model includes internal (e.g. an investigation of the underlying theory) and
external (e.g. a comparison of the results with experimental data) validation, and addresses the evaluation of the respective software. It should focus not
only on the predictive capability of a model, but also on the strength of the theoretical underpinnings, evidence supporting the model?s conceptualisation, the
database and the software. The external validation was performed using a set of reference substances with different physico-chemical properties and use
patterns. Additionally, sensitivity and uncertainty analyses were carried out, and alternative models were discussed. Recommendations for improvements
and maintenance of the risk assessment methodology were presented. To perform the software evaluation quality criteria for risk assessment software were
developed.
From a theoretical point of view, it was shown that the models strongly depend on the lipophilicity of the substance, that the underlying assumptions
drastically limit the applicability, and that realistic concentrations may seldom be expected. If the models are applied without adjustment, high uncertainties
must inevitably be expected. However, many cases were found in which the models deliver highly valuable results. The overall system was classified as a
good compromise between complexity and practicability. But several chemicals and classes of chemicals, respectively, with several restrictions were
revealed: The investigated models used to assess indirect exposure to humans are in parts currently not applicable for dissociating compounds, very polar
compounds, very lipophilic compounds, ions, some surfactants, and compounds in which metabolites provide the problems and mixtures. In a strict sense, the
method is only applicable for persistent, non-dissociating chemicals of intermediate lipophilicity. Further limitations may exist. Regarding the software, it
was found that EUSES basically fulfils the postulated criteria but is highly complex and non-transparent. To overcome the inadequacies a more modular design is proposed.
| Identifer | oai:union.ndltd.org:uni-osnabrueck.de/oai:repositorium.ub.uni-osnabrueck.de:urn:nbn:de:gbv:700-2000090413 |
| Date | 04 September 2000 |
| Creators | Schwartz, Stefan |
| Contributors | Prof. Dr. rer. nat. Michael Matthies, Prof. Dr. rer. nat. Stefan Trapp |
| Source Sets | Universität Osnabrück |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis |
| Format | application/zip, application/pdf |
| Rights | http://rightsstatements.org/vocab/InC/1.0/ |
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