Registration Dossier
Registration Dossier
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EC number: 201-143-3 | CAS number: 78-79-5
Biodegradation in water: screening tests
Administrative data
Link to relevant study record(s)
Description of key information
Using a weight of evidence approach, isoprene is expected to be rapidly biodegradable and potentially readily biodegradable.
In a key study, conducted in accordance with OECD TG 301F and GLP. An average of 61% degradation was observed across 3 replicates which also met the 10 -day window which in most circumstances would mean the substance can be classified as readily biodegradable. However, the variability between the replicates exceeded 20% which according to the guidelines warrants a repeat of the test. Therefore, this test demonstrated the ability for isoprene to rapidly degrade but the data are insufficiently robust enough to support a conclusion of ready biodegradability. It should however be noted that it is not possible for this test to show a false positive due to the strict nature of the test conditions and so this study shows a strong possibility for the substance to be readily biodegradable.
Supporting studies are also available that show the substance could potentially be readily biodegradable. In an additional OECD TG 301D Closed Bottle test, 60% biodegradation was measured in one replicate on day 18. On day 28, the average biodegradation between two replicates (2 and 58%) was 30%. Therefore, the criteria for ready biodegradability were not met. A maximum extent of 64% biodegradation was measured on day 7 of a supplementary investigation, which confirms that isoprene can be rapidly biodegraded in the presence of an acclimated inoculum. The test substance showed no inhibitory effect on the normal degradative activity of the microbial inoculum in the supplementary study.
This is further supported by QSAR modelling using the Biowin and BioHCwin models which show the substance is likely to be readily biodegradable.
In conclusion. the substance is considered readily biodegradable based on the strong evidence in the key study that it is potentially readily biodegradable, which is supported by the supplementary studies and QSAR models.
Key value for chemical safety assessment
- Biodegradation in water:
- readily biodegradable
Additional information
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