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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Of the four main constituents of the reaction mass three, n-hexane (CAS No. 110-54-3), cyclohexane (CAS No.110-82-7) and toluene (CAS No. 108-88-3) are readily biodegradable. The fourth main constituent 4-vinylcyclohexene (CAS No. 100-40-3) is not readily biodegradable.

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Additional information

Reliable biodegradation screening data is available for two of the main components of the reaction mass, cyclohexane (CAS No. 110-82-7) (Exxon Biomedical Science Inc, 1995) and 4-vinylcyclohexene (CAS No. 100-40-3) (MITI, 1992). The results from these studies indicate that cyclohexane is readily biodegradable and 4-vinylcyclohexene is not readily biodegradable.

Several standard biodegradable test using sewage sludge inocula (Price et al, 1974; Bridie et al., 1979) show a third main component, toluene (CAS No. 108-88-3), to be readily biodegradable. Although these studies do not follow current standard guidelines they are sufficient to demonstrate that toluene is readily biodegraded by both non-adapted and adapted sewage sludge inocula. These two studies were also used as part of a weight of evidence that toluene is readily biodegradable in the EU RAR for toluene (2003). In the absence of reliable experimental studies, the biodegradation potential of the fourth main component, n-hexane (CAS No. 110-54-3), was predicted using the QSAR models, Biowin and BioHCwin. Both models predict n-hexane to be readily biodegradable.