Evaluation of Tier 1 Exposure Assessment Models under REACH (eteam) Project – Substudy Report on Uncertainty of Tier 1 Models

In this work package of the eteam project different aspects of the tools were evaluated which may lead to an uncertainty of the model estimate, i.e. a deviation of the estimate from the actual exposure value at a workplace. For this purpose a qualitative approach as suggested by the WHO and the corresponding REACH guidance document about uncertainty assessments was used. In order to assess the overall uncertainty, a matrix was developed for each model, which includes a list of all possible sources of uncertainty and a categorisation of different aspects (e.g. transparency and uncertainty of the knowledge base). The different aspects were then discussed and compared. As a result it was shown that for each tool a number of possible sources of uncertainties exists, however, it has to be taken into account that it always depends on the model and the situation itself which sources of uncertainty are dominant and how uncertain the final exposure estimate may be.