5-propyloxan-2-one

Endpoint summary

Description of key information

According to the key ready biodegradability test (OECD Guideline 301B with GLP compliance, 2019), the registered substance attained 88 % biodegradation after 28 days of incubation and satisfied the 10 -day window validation criterion. Therefore, the substance is readily biodegradable.

Two other studies are available and were performed on the registered substance:

- An OECD Guideline 301F study (Guangdond Detection Center of Microbiology, 2012), assessed as a supporting study and showed a mean of 67.6% biodegradation after 28 days of incubation but does not fulfill the 10 -day window validation criteria. From the graph, 60% of biodegradation seems to be reached just after the 10-day window, on the 18th day of experiment (with the measurement just below 10% occurring on day 7).

- An OECD Guideline 301D study (Phytosafe, 2008), assessed as an invalid disregarded study. In this study, 50% biodegradation was observed after 36 days of incubation. As the substance was dissolved in a partially biodegradable solvent, it cannot be ascertained directly to what extent the chloroform degradaded in the solutions containing test substance. Consequently, the results of the study are not interpretable and the study is considered technically invalid.

Additional information

To assess the ready biodegradability of the registered substance, three studies are available.

The first study, from Covance, 2019, assessed as the key study (klimisch 1), was performed on the registered substance according to OECD Guideline 301B and EU Method C.4-C with GLP compliance. The substance, at a concentration of 10 mg carbon/L, was exposed to activated sewage sludge micro-organisms with mineral medium in sealed culture vessels in the dark at temperatures of between 21 and 24 °C for 28 days. The biodegradation of the test item was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the reference item, sodium benzoate, together with a toxicity control were used for validation purposes. The test substance attained 88% biodegradation after 28 days and satisfied the 10-day window validation criterion, whereby 60% biodegradation must be attained within 10 days of the biodegradation exceeding 10%. The substance can therefore be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301B.

The second study, from Guangdong Detection Center of Microbiology, 2012, assessed as the supporting study (klimisch 2), was performed on the registered susbstance according to OECD Guideline 301F with GLP compliance, and according to the Chinese Guideline 301F Ready Biodegradability: Manometric Respirometry test. Activated sludge was exposed to the test substance at a concentration of 21.4 mg/L, with culture medium, for 28 days, in aerobic conditions. According to this test, the degree of degradation, calculated from the O2 consumption of two replicates was 62.5 % and 72.7 % respectively, mean of 67.6 %, after 28 days, but without the 10 -day window. Thus, the test substance should be regarded as readily biodegradable but failling the 10-day window criteria. More measurements could have been made during the 10 -day window, allowing a better evaluation of the 10 -day window criteria.

The third study, from Phytosafe, 2008, assessed as a disregarded study (klimisch 3), was performed on the registered substance according to the EU Method C.4-E: Determination of the ready biodegradability - Closed bottle test. The test material was exposed to inoculum from surface waters, at a concentration of 2.04 mg/L in Test 2, in culture medium, in closed bottles, in the dark, at 20 +/- 1 °C, for 36 days. The degradation of the test substance was assessed by the measurement of oxygen consumption. The validity criteria were fulfilled for Test 2, for a concentration of test substance of 2.04 mg/L. 50 % biodegradation occurred within 36 days and the 10-day window criteria was not fulfilled, even if the pass-level was almost reached. However, in both tests, the test substance was dissolved in a partially biodegradable solvent, chloroform was used to prepare a "stock solution" prior to adding an aliquot of this solution to the mineral medium. The biodegradation of the solvent in the test substance solutions was determined by substracting the degradation in a solvent control. However, it cannot be ascertained directly to what extent the chloroform degraded in the solutions containing test substance, the results of the study are not interpretable and the study is considered technically invalid. Consequently, the test cannot be considered valid.

In conclusion, based on the key study, the registered substance is readily biodegradable.