In regulation of chemicals in Europe NER in degradation testing are an issue. In European regulations it is treated incoherently with REACH considering NER as non-degraded substance if not proven otherwise while other, e.g. plant protection product regulation, consider NER as degraded up to now. As this might have significant impact on degradation half-lives determined, the German Environmental Agency is working on a harmonized approach. However, a standardized method for further characterization of NER is still lacking. In the last years efforts have been made to differentiate NER into different categories of concern. A first approach was started on behalf of the German Environment Agency (UBA) in 2013. In September 2018 a follow up project was initiated by UBA order to harmonise those project results with the procedures described in the ECHA discussion paper on NER, published in June 2018 on experimental approaches to distinguish sequestered (type 1 NER), covalently bound (type 2 NER) and biogenic NER (type 3 NER). A parallel project was initiated by Concawe, which is closely related to the UBA project, but focusses on petroleum specific chemicals and includes additional bioavailability determinations to get a better understanding on relevant processes. In the UBA project we evaluate the applicability of the harmonised approach experimentally, supported by data from the Concawe project. We run these experiments using test substances labelled with 13C and 14C in parallel. In case of a positive correlation, data from literature using either label can be reconciled. Experiments are accompanied by the modelling tool Microbial Turnover to Biomass (MTB) that uses released CO2 as indicator of microbial degradation and the theoretical biomass yield in order to estimate the biogenic NER formation. Experimental data determined in the current project shall be used to verify the outcome of this approach. We test a set of four substances in a standard OECD 307 approach. Different procedures for exhaustive extraction are applied in order to compare current NER definitions. NER are subject to a set of harsh extraction methods in order to identify and quantify the different NER types described in the ECHA discussion paper.

Analysis of non-extractable residues (NER) for use in chemical persistency assessment – experimental results from a harmonised testing procedure

ACS Fall 2020 Virtual Meeting

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