Reaction mass of m-terphenyl and o-terphenyl

PBT assessment

PBT assessment: overall result

PBT status:

the substance is PBT / vPvB

Justification:

At least o-terphenyl fulfils both vP and vB criteria. As o-terphenyl occurs in significant concentrations in the UVCB substance (> 50 %), the UVCB “reaction mass of m-Terphenyl and o-Terphenyl” is considered to fulfil vPvB criteria.

The UVCB substance was assessed by evaluating the different relevant constituents present in the substance. Detailed information in provided in Section 8 of the CSR. 

The group level is used to group the constituents into groups of “similar” constituents (see Table 1 of CSR for an overview of the different groups, what they contain and their concentration range). For the UVCB under discussion one group was identified:

Group T: the group containing the terphenyl constituents,

Justification of vPvB classification for o-terphenyl:

vP: For ortho-terphenyl and meta-terphenyl, the potential for primary and ultimate degradation is demonstrated in studies on ortho-terphenyl. According to the approach of the study authors the half-life for disappearance of parent substance is below the threshold for freshwater and the original calculations based on study results revealed very short dissipation half-lifes- demonstrating that the mixture as tested does not persist in soil. Based on recent evaluation results of the eMSCA, the modelling approach chosen by the study authors was not appropriate to describe the degradation of the compound in soil. According to the outcome of remodelling of the study results by the eMSCA terphenyl fulfils the vP criterion in soil based on the degradation study by Monsanto Company (1989) and remodelling by eMSCA. The different isomers of terphenyl, quaterphenyl, and polyphenyl were not differentiated in this study. Nevertheless the reliability of this soil dissipation test is limited due to the fact that information on the composition of the tested mixture is missing. In general eMSCA considers that degradation of a hydrocarbon in a mixture study (such as Monsanto Company (1989)) may be overestimated compared to testing of each constituent separately (due to co-metabolism). However, in the present case the possible overestimation is acceptable as the half-life for terphenyl fulfills the vP criterion. In a CO2-evolution study of Bayliss (2018) according OECD 301B the UVCB "reaction mass of m-Terphenyl and o-Terphenyl" (concentration 10 mg carbon/L) attained 11% biodegradation after 28 days and therefore cannot be considered to be readily biodegradable.

vB: For ortho-terphenyl, information on the bioaccumulation is available from different sources. Based on the measured BCF-values in Rainbow trout (Schlechtriem 2017, NITE 2012), it can be concluded that o-terphenyl fulfils the B and vB criterion. This conclusion is supported by measured BMF values (OECD 2012, Inoue 2012), which predict BCF values around 2000 and even over 5000. QSAR models predict BCF values around 2000, being in concordance with the measured BCF values on Carp, further supporting the conclusion. It should however be noted, that in several other guideline-compliant studies from different labs, values clearly below 5.000 supporting the assessment as B but not vB were found. In addition, it was also mentioned in the dossier, that the intention of the study by Schlechtriem was to test a specific dosing regimen and more important, that there were significant and relevant deviations from the guideline, having a potential impact on the outcome of the study (significant higher growth rate, potentially also increasing the BCF values obtained).