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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

OECD Guideline 301F, EU Method C.4-D, GLP, Key study, validity 1:
79% biodegradation after 28d without strictly 10d window in one replicate (59% biodegradation at the end of the 10d window).
Considered as readily biodegradable based on supporting evidence on two analogue materials.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

To assess the ready biodegradability of the registered substance, METHYL CIS-3-OXO-2-PENTYL-1-CYCLOPENTANE ACETATE, three valid studies are available.

The first study (Eisner, 2010a), assessed as the key study, was performed on the registered substance according to OECD Guideline 301F and EU Method C.4 -D with GLP statement. The test substance at a concentration of 101 mg/L in two replicates was exposed to activated sewage sludge micro-organisms with culture medium for 28 days, under aerobic conditions. The degradation of the test substance was assessed by the measurement of daily oxygen consumption. Control solutions with inoculum and the standard material, sodium benzoate, together with a toxicity control were used for validation purposes. The toxicity control show that the test substance had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 100 mg/L. In the procedure controls, the reference item, sodium benzoate, was degraded by an average of 90% by exposure day 14, and reached an average biodegradation of 93% by the end of the test (day 28), thus confirming suitability of the activated sludge. At the end of the 28-day exposure period, the mean biodegradation of the test substance amounted to 79%. Consequently, the substance was found to be highly biodegradable under the test conditions within 28 days. However, the stringent pass level for ready biodegradability (i.e. biodegradation of at least 60% of the ThOD in a 10-day window within the 28-day period of the test) was marginally not reached by a few hours in one replicate (at the end of the 10-day window the biodegradation of the test substance reached about 59%). Nonetheless, the mean value of the two replicates met the 10 day window criterion and the assessment may conclude that the substance is “readily biodegradable”. Furthermore supporting evidence is available, in the form of data on analogue materials.

The second study (Rudio, 1994), assessed as a supporting study, was performed on a read-across substance, METHYL 3-OXO-2-PENTYL-1-CYCLOPENTANE ACETATE (quality High Trans isomer), according to OECD Guideline 301F with GLP statement (but without certificate). This read-across substance is a mixture of two diastereomers, approximately 10% cis- and 90% trans-diastereomers which cis-diastereomer corresponds to the registered substance. The test substance undergoes 89 % biodegradation after 28 days in the test conditions. Furthermore, the biodegradation rate reached at the 10-day window is 82 %, which exceeds the pass level of 60 %. This means that the test substance is readily biodegradable. The curves obtained with the reference substance, aniline, alone and with the test substance plus aniline show no toxic effect of the test substance on the microorganisms at the test concentration (100 mg/L).

The third study (Eisner, 2010b) assessed as a supporting study, was performed on a read-across substance, METHYL 3-OXO-2-PENTYL-1-CYCLOPENTANE ACETATE (quality High Cis isomer), according to OECD Guideline 301F and EU Method C.4 -D with a GLP statement. This read-across substance is a mixture of two diastereomers, approximately 71 to 76% cis- and 20 to 25% trans-diastereomers of which the cis-diastereomer corresponds to the registered substance. At the end of the 28-day exposure period, the mean biodegradation of the test substance amounted to 85%. Furthermore, the biodegradation rate reached after the 10 -day window was 68% (on average), which exceeds the pass level of 60%. This means that the test substance is readily biodegradable. The curves obtained with the reference substance, sodium benzoate, alone and with the test substance plus sodium benzoate show no toxic effect of the test substance on the microorganisms at the test concentration (100 mg/L).

In conclusion, based on the evidence from three studies including two analogue materials, the registered substance, METHYL CIS-3-OXO-2-PENTYL-1-CYCLOPENTANE ACETATE, can be considered as readily biodegradable.

These supporting substances are considered adequate for read-across purposes based on similar physico-chemical properties between the registered substance and the two analogue materials used, and the same readily biodegradability potential.

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