Evaluation and application of models for the prediction of ready biodegradability in the MITI-I test

Three existing models and one newly developed model for the prediction of ready biodegradability of organic compounds are evaluated by comparing the descriptors they use, and the consistency of the models when applied to the set of High Production Volume Chemicals (HPVC) in the European Union. Linear regression models developed for the OECD showed the best performance in the external validation (84.7 per cent correct), although comparison with the other three models is flawed because of the class specificity of these models. With these models 567 of the 894 compounds could be predicted in the validation. The multivariate statistical model showed the performance in the external validation (82.7 per cent correct)combined with the broadest applicability of the model. The evaluation of the predictions of the models for the HPVC shows that all models are highly consistent in their prediction of not-ready biodegrability, but much less consistency is seen in the prediction of ready biodegrada bility. This com plies with the observation that all 4 models show better performance in their predictions of not-ready biodegradability.