There is general agreement that the formation of non-extractable residues (NER) in soil or sediment can have a significant impact on a chemical’s behaviour in the environment and it is therefore important that they should form an integral part of the environmental risk assessment (ERA) of chemicals. However, the significance of NER and exactly how they should be considered in ERA remains unclear. There are two contrasting views of the role of NER. On the one hand, NER represents a hidden fraction of the original chemical capable of subsequent release and potentially causing harm. On the other hand, NER represents an effective and safe method of rendering the chemical innocuous and allowing slow degradation in the bound state to products that pose no harm. These contrasting views remain and guidance on how to incorporate information on NER into environmental risk assessment is lacking.
This ECETOC task force has established a scheme to be used in the environmental risk assessment of NER. The task force has, where possible, suggested trigger values and provided further guidance on how to incorporate NER into ERA. The scheme includes a Tiered approach and has used case studies to demonstrate how it may be used as a practical approach to incorporating NER into the ERA of chemicals. Whilst the task force has developed this scheme, knowledge gaps remain where further work is required and these have been highlighted in the report.