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EC number: 203-438-2
CAS number: 106-88-7
An experimental study was conducted to assess the biodegradability of the test item according to the guideline ISO 14593 (Draft, 1996). 4 mg/l inoculum of activated sludge (municipal sewage) were exposed to a concentration of 34 mg/l test item for 28 d in closed bottes. The CO2 evolution was determined weekly as TIC (Total inorganic carbon). After 28 d 80-90 % degradation was observed. All validity criteria were fulfilled and the test item can be rated as readily biodegradable according to OECD criteria.
The biodegradability of the test item was examined under aerobic conditions using the DOC (dissolved organic carbon) Die-Away Test, OECD Method 301 A. This method consisted of a shake flask biodegradation test with defined medium. For the test item, an average of 90% of the material was degraded in the viable reaction flasks after 28 days. For a compound to reach the "pass level", >70% biodegradation must be reached within 10 days of the start of biodegradation. By definition, biodegradation starts when the percent degradation exceeds the 10% level. In this study, loss of butylene oxide in the viable reaction mixtures exceeded the 10% level at day 5. However, 70% degradation was not achieved until day 19. Therefore, the test item did not meet the OECD criteria for ready biodegradability and cannot be classified as readily biodegradable. Benzoate was included as a positive control to ensure the viability of the inoculum Benzoate was extensively degraded after three days (e.g. 73% removal) thus confirming the viability of the inoculum. A separate control, containing benzoate and butylene oxide, was included to evaluate the toxicity of the test chemical to the inoculum. The presence of the test material did not appear to have a significant effect on the DOC removal capacity of the inoculum indicating no apparent toxicity of the test item. The removal of DOC as butylene oxide was biologically mediated, since DOC removal in the killed (abiotic) controls was <1% at the end of the study (28 d).
An experimental study according to OECD guideline 301C and GLP regulations was conducted to assess the biodegradation potential of the test item. A mixture of sewage, soil and water in an initial concentration of 30 mg/L was exposed to the test item with a concnetration of 100 mg/L for 28 d. The biodegradation based on the O2 consumption was measured. After 28 days 109 % of the test item was degraded as mean of three replicates regarding the BOD. The test item can be considered readily biodegradable.
In a CO2-Headspace Test according to ISO 14593 the substance was determined to be readily biodegradable in compliance with OECD criteria (80 - 90 % biodegradation based on CO2 evolution) fulfilling the 10-day-window criterion [BASF AG, 1999].
The ready biodegradability of the test item was investigated in three different screening tests, a headspace test according to ISO 14593 guideline (further on OECD 310), which base on the detection of CO2 evolution [BASF, 2000], a test from the Ministry of International Trade and Industry (MITI I, OECD 301C), which base on the measurement of oxygen consumption [MITI, 1997] and additional a DOC-Die-Away test according to OECD guideline 301 A [Dow, 1999]. As it is required for ready tests the used inoculum was not adapted in all three cases. Since the test item is moderately volatile (Henry’s law = 21.48 Pa.m3/mol) [EPIwin calculation, 2017], closed systems were indicated for testing the biodegradability. The headspace test (ISO 14593) and the MITI I test (OECD 301C) are commonly prepared in closed systems, whereas the DOC-Die-Away test (OECD 301A) is usually prepared in an open test system. In case of testing the test item, the DOC-Die-Away test (OECD 301A) was exceptionally prepared in a closed test system. Therefore, specially designed 1 liter shake flasks were used, which were filled with 500 mL mineral medium and a sufficient amount of test substance. After closing the test flasks the remaining space results into a headspace volume of air. In both studies with closed flasks (ISO 14593 and OECD 301A) abiotic controls were performed to assess volatilization processes. There was no indication of volatilization during the 28 days incubation period.
In all three reported guideline studies the pass level for ready biodegradabilityof 1,2-epoxybutane was reached within the required 28 days’ time period. Besides reaching the pass level within 28 days, the ready criteria include the requirement on achievement of the pass level within ten days from the onset of biodegradation. This so-called 10-day-time window requirement applies not to all test systems. MITI I (OECD 301C) is excluded from the ten-day-time window requirement. Hence from the result of the reported MITI I test the test item can be stated as ready biodegradable according to OECD criteria. In the headspace test according to ISO 14593 guideline the detection of the 10-day-time window turned out to be difficult, since the kinetic was recorded in 7 days measuring intervals. From the resulting curves it can be assessed, that the lag phase lasted for about 8 to 10 days and the pass level was reached after approximately 19 to 20 days. Since it was not possible to determine more precise time points, it is not definitely been proved that the 10-day-time window was hold. To take this lack of definition into account, the OECD guidelines permit in case of the Closed Bottle test (OECD 301D), which usually base also on a 7-days measuring interval, to use a 14-days window instead of a 10-day-time window. In the described headspace test the time window is very close to 10 days and a 14-days window was definitely hold. Therefore, in the study report of the headspace test (ISO 14593) of the test item is stated as readily biodegradable. The ready results from the MITI and from the headspace test are complimented by the results of the DOC-Die-Away test. At the end of the DOC-Die-away test the degradation exceed 90%, but missing the 10-day-time window.
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