Current issues and challenges faced on the PBT working group with respect to persistence
The PBT working group discussed under the interim strategy period before REACH around 120 existing substances and also several new substances and biocides. The assessment conclusion ‘not persistent’ for existing substances was drawn in equal amounts from biodegradation screening information and other information (e.g. abiotic degradation, information about reactivity). For a large number of the substances, the discussions consisted of considerations on the validity of available data in the light of the physico-chemical (PC)-properties and chemical reactivity. In discussion on available experimental degradation studies the relevance of the test conditions for PBT assessment was crucial. Conventions established at that time were incorporated into ECHA’s guidance, but for some paths (photodegradation, anaerobic biodegradation, hydrolysis, bound residues) uncertainties still remained in terms of whether and how to use the respective data in the context of PBT assessment.
Experience gained with substances like endosulfan shows that persistence in one compartment may still be significant although testing information of a specific path such as hydrolysis would primarily indicate rapid degradation.
A year ago about 150+ registered substances were prioritised for further PBT screening assessment by EU Member State experts as an activity beyond the formal REACH processes. The basis for the prioritisation was mainly QSAR estimations due to lack of experimental data. It seems that the main part of the ongoing PBT assessment work of the EU Member State experts will cover similar aspects as the PBT assessment work in the past. This screening and assessment work carried out by the EU Member State experts and ECHA is, among others, discussed in ECHA’s PBT Expert Group, which had its first meeting in February 2012. The group is an informal scientific expert group. The work is planned to be extended in future to cover unknown, variable composition or biological (UVCB) substances. It has not been possible so far to cover UVCBs in the PBT screening activities in a balanced way.
The first amendment of REACH Annex XIII, which the registrants must comply with by March 19, 2013, extended registrant’s obligations regarding the PBT assessment. Although CoRAP (Community Rolling Action Plan under REACH) remains the most powerful tool for requiring more information for the PBT assessment, the role of dossier compliance check may become more important than it is today as one of the tools for clarifying the PBT concern of a substance. The amendment of REACH Annex XIII also introduced into the legal text the scientific principles of the PBT assessment which were developed and applied by the former PBT WG. Nevertheless, a long list of scientific issues remains to be elaborated by ECHA’s PBT Expert Group for the further development of the PBT assessment. Following issues can be mentioned as examples:
- identifying the compartment of concern, - role of aquatic photodegradation,
- influence of the form of test item,
- improving understanding of the fate of substances (e.g. how to identify very persistent substances which form very slowly PBT substances),
- sediment issues,
- role of anaerobic biodegradation,
- use of monitoring data from contaminated sites
The substances so far identified as PBT/vPvB by ECHA’s Member State Committee in accordance with REACH Article 59 cover different types of substances which therefore have been assessed for persistence with different approaches. Finally, when looking at the substances identified as PBT/vPvB previously and under REACH, it seems that during the assessment of persistence field monitoring data has played an important role as supporting information.