2,2,5-trimethyl-5-pentylcyclopentan-1-one

Biodegradation in water: screening tests

Description of key information

Weight of evidence approach using experimental study (OECD Guideline 301D, no-GLP) and QSAR data (Biowin v4.10):
Not readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

To assess the ready biodegradability of the registered substance, a weight of evidence approach was used based on one experimental study and one QSAR.

The experimental study (AkzoNobel, 2012) was performed on the registered substance according to OECD Guideline 301D but without GLP statement. The test substance (at 2 mg/L) was exposed to two inocula, activated sewage sludge microorganisms and river water, with culture medium in closed bottles in the dark at 22-24°C for 7, 14, 21, 28, 42, 56 and 84 days. The degradation of the test substance was assessed by the measurement of oxygen consumption. According to the results of this study, the test substance is partially degradable. The test substance undergoes 14-21% and 51-55% biodegradation after 28 and 84 days, respectively, depending on the inoculum used. Thus, the test substance should be regarded as not readily biodegradable according to this test. However, the degradation observed strongly suggests that it is primarily biodegradable within 28 days.

The QSAR data was performed on the registered substance. The model used is Biowin v4.10, plug-in from EPISUITE v4.1 from US EPA. This model is recommended by the ECHA guidance document on information requirements and is well documented with regard to validation parameters according to OECD principles. Moreover, the substance is fully characterised for the applicability domain. The Biowin 3 result is "weeks-months", therefore it's expected that the substance is not readily biodegradable but this result nevertheless supports the conclusion that biodegradation of the substance can be anticipated over time.

In conclusion, as we obtained the same results between the experimental and the predicted data, we can conclude, based on this weight of evidence approach that the registered substance is not readily biodegradable but that the degradation observed strongly suggests that it is primarily biodegradable within 28 days.

In addition, in a preliminary biodegradability test performed on the registered substance and available in the bioaccumulation study report (Kyushu, 1986), no sign of possible biodegradability was observed at 100 ppm of test substance. This test was performed in July 1980 by Chemical Inspection & Testing Institute, Japan, and is considered as non official since the test was not done following official standard method.