Consideration of non-extractable residues (NER) in PBT-assessment

The formation of NER in simulation studies on degradation in the environment is an issue addressed in all European regulations on chemical substances. Some of these residues can be released back into the environment over the long term. This proportion must therefore be considered in the persistence assessment. The project summarised existing proposals for characterising the different NER types. The extraction methods proposed for determining the total NER and for differentiating into NER types I (strongly sorbed or physically entrapped), NER type II (covalently bound) and NER type III (biogenically bound) were tested and refined for practical suitability. An evaluation concept was developed to determine the proportion of NER that can be remobilised in the long term (NER type I), taking this into account in the persistence assessment. The report is aimed at regulators, industry and academia.