Proposals to overcome limitations in the EU chemical risk assessment scheme

The notification of new chemicals in the European Union requires a risk ass essment. A Technical Guidance Document (TGD) was prepared for assistance. T he TGD proposes QSARs, regressions and models from various sources. Each me thod has its own range of applicability and its own restrictions. Regressio ns used in the assessment of indirect human exposure have a common regressi on range from log K-OW 3.0-4.6. Most models are compartment models, which d o not consider a spatial distribution of the chemical, and were originally developed for non-dissociating, lipophilic persistent chemicals with measur able vapor pressure. Taking this into account, the TGD is only applicable f or a minority of chemical classes. Dissociating compounds, ions, polar and very non-polar compounds do not belong to them. The effect of mixtures cann ot be considered, except for hydrocarbons. Using the example of plant uptak e, it is shown that in certain cases uptake is underestimated by the model due to processes not considered. This may lead to a wrong security in risk assessment. To overcome these limitations, a set of alternative models with different application ranges should be developed. When no applicable metho d is available, it might be better not to use a model at all instead of an inadequate model, and look for other sources of information. (C) 2000 Elsev ier Science Ltd. All rights reserved.