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Environmental fate & pathways

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Biodegradation studies are not available for the Reaction Mass of Ethylbenzene and m-Xylene. However, it is difficult to assess the persistence of the substance using standard test methods as the tests measure the properties of the whole substance but do not provide information on the individual constituents. Instead, it is more appropriate to consider whether the representative components of these streams are persistent. Therefore, data has been read across from the xylene isomers and ethylbenzene as these are the major constituents of the substance.

Data are available for all three xylene isomers from GLP-compliant guideline studies (Dr Noack 2015). The studies followed OECD guideline 301F (ready biodegradability: manometric respirometry test) using a mixture of sewage and soil micro-organisms. m-xylene reached 60% biodegradation after 5 days and 98% biodegradation after 28 days. o-xylene reached 60% biodegradation after 8 days and 94% biodegradation after 28 days. p-xylene reached 60% biodegradation after 7 days and 90% biodegradation after 28 days. The studies show that the xylene isomers are readily biodegradable, meeting the 10 day window criterion.

The EU RAR (2007) concludes that ethylbenzene is readily biodegradable. The Risk Assessment Report is peer-reviewed by the Scientific Committee on Toxicity, Ecotoxicity and the Environment (CSTEE), now renamed Scientific Committee on Health and Environmental Risks (SCHER) which gives its opinion to the European Commission on the quality of the risk assessment. This Draft Risk Assessment Report has undergone a discussion in the Competent Group of Member State experts with the aim of reaching consensus by interpreting the underlying scientific information.

In addition to the key studies, additional supporting data on the biodegradability of the xylene isomers and ethylbenzene are available from a number of sources. Overall, the available data have been used to conclude that ethylbenzene and the xylene isomers, and therefore the substance itself, are readily biodegradable and thus not Persistent (P) or very Persistent (vP) based on the screening criteria for persistence stipulated in ECHA's Guidance on information requirements and chemical safety assessment - Part C: PBT Assessment (2008).