Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

Not readily biodegradable, but considered as inherently biodegradable as determined in the key study (OECD 301F, 53% in 28 days). Similar levels of degradation were observed in two supporting studies (OECD 302C, extended 56 d OECD 301B). 

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

The ready biodegradability of the substance has been determined by the Manometric Respirometry Method (OECD 301F). In this key study, Strawberry Pure underwent 53 % degradation after 28 days and must be regarded as not readily biodegradable. The REACH guidance on Information Requirements R.7b states “When results of ready biodegradability tests indicate that the pass level criterion is almost fulfilled (i.e. ThOD slightly below 60 %) such results can be used to prove inherent biodegradability". Therefore the substance is considered to be inherently biodegradable.

Similar levels of degradation were observed in two supporting studies: 49.6 % after 56 days in a modified OECD 301B study (sealed CO₂ evolution test with only this time-point examined) and 53 % after 28 days in a study to OECD 302C guideline (Inherent Biodegradability: Modified MITI Test (II)).

Time plots, available for two studies, show a possible plateau towards the end of the test indicating that either stable metabolites may have been formed or that the test substance and/or degradation products were lost from the test system.

Probable biodegradation pathways have been simulated using the CATALOGIC 301C v.07.08 model. The model provides results for % BOD (biological oxygen demand) and quantities of parent and biodegradation products. It predicts that Strawberry Pure will achieve 33.5 % BOD and that 0 % of the parent will remain at the end of a 28 day ready test (i.e. Strawberry Pure will undergo complete primary biodegradation). Four metabolites are predicted to have a lower probability to metabolise than the parent: ethyl 2,3-dihydroxy-3-phenylbutanoate, 2,3-dihydroxy-3-phenylbutanoic acid, 2-hydroxy-2-phenylpropanoic acid and benzene. The predicted quantities of these metabolites at the 28 day time-point are 10.5 %, 20.4 %, 15.6 % and 48.4 % respectively. Since the model underestimates the % BOD of Strawberry Pure compared to the observed degradation levels of 50 to 55 % it is likely that the quantity of metabolites at the end of the 28 day test would be lower than predicted. In addition benzene is known to be subject to rapid volatilization when released to water [1], which could explain the plateau observed at the end of biodegradation studies (i.e. the substance is lost from the test system into the headspace and is not available for further biodegradation). The remaining 3 metabolites, which have a higher probability to metabolise than benzene, would be expected to biodegrade further to produce benzene. There is evidence that benzene may be subject to biodegradation under certain environmental conditions and that it is photodegraded [1].

Reference: [1] http://www.epa.gov/ogwdw/pdfs/factsheets/voc/tech/benzene.pdf