Registration Dossier
Registration Dossier
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EC number: 287-502-5 | CAS number: 85536-20-5
Biodegradation in water: screening tests
Administrative data
Link to relevant study record(s)
Description of key information
Based on read across from the xylene isomers, and the EU RAR's assessment of ethylbenzene, the streams in this category are considered to be readily biodegradable
Key value for chemical safety assessment
Additional information
Biodegradation studies are not available for any of the streams in this category. However, it is difficult to assess the persistence of UVCB streams 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 components of the streams in this category.
Exxon Biomedical Sciences (1995) conducted an OECD 301F test with p-xylene. This GLP-compliant guideline study found p-xylene to be readily biodegradable with >60% biodegradation by day 10. Exxon Biomedical Sciences (1996) conducted a GLP compliant guideline study with o-xylene. Although >60% biodegradation was observed within 28 days the 10 day window criterion was not met. Therefore, this study does not demonstrate that o-xylene is readily biodegradable but does indicate that it has the potential to biodegrade.
Bridie et al (1979) report the results of a 5 day BOD/ThOD test. This study predates the implementation of GLP and the OECD guidelines for biodegradation screening tests. The study authors report that they followed guidelines in operation at the time, although the level of detail in the publication is very limited. In particular the concentration of the test substance is not reported. Despite these limitations, this study does demonstrate that the xylene isomers can be biodegraded by non-adapted sewage sludge. The results of this study indicate that the xylene isomers degrade with a 5 day BOD/ThoD in the range of 44 to 80%. These results suggest that all three isomers are likely to meet the criteria for ready biodegradability.
MITI (2001) reports that 100% biodegradation (based on BOD and GCMS) was observed in an OECD 201C study with m-xylene. In a second study with p-xylene 38% biodegradation based on BOD and 92% biodegradation based on GCMS analysis was reported. We have been unable to obtain copies of these reports so have not been able to assess their reliability.
The EU RAR for ethylbenzene (EU, 2008) concludes that the substance is readily biodegradable. CITI (1992) also report that ethylbenzene meets the criteria for inherent biodegradability.
Overall, these studies demonstrate that the xylene isomers and ethylbenzene, and therefore the streams in this category, can be considered to be readily biodegradable.
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