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Environmental fate & pathways

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Two studies were available and were selected as key studies, because they were quoted with reliabilty 1 according to Klimisch scale, and followed the recommended OECD guidelines 301D and 301F respectively.

In the first study (CIT, 2004), the aim was to assess the ready biodegradability of the substance Guetol in a closed bottle test following recommended guidelines (OECD 301D).

The inoculum used for this test was a non-adapted inoculum collected from a domestic water treatment plant. After filtration it was diluted into OECD mineral medium to reach 10E4 cells/mL of bacteria. Mineral medium was aerated prior testing in the test room.

Inoculum blank, toxicity control, procedure control and test vessels were measured for O2 consumption in duplicate in bottles on day 0, 3, 7, 10, 14, 17, 21, 24, and 28. The reference substance used was acetate sodium.

O2 concentrations, biodegradation values in replicate at the end of the 10d-window, toxicity control and procedure control criteria were fulfilled and thus validated the test. The 10d-window started on day 4 and 47% of the substance degraded after 14 days of test. After 28 days of test, 72% of the substance degraded. The substance was therefore found inherently biodegradable.

In the second one (Harlan, 2010), the test item GUETOL was investigated for its ready biodegradability in a manometric respirometry test over 28 days (Harlan, 2010), according to the EU Commission Directive 92/69EEC, C.4-D, Commission Regulation (EC) No 440/2008, C.4‑D and the OECD Guideline for Testing of Chemicals No.301 F.

 

The percent biodegradation of the test item was calculated based on the theoretical oxygen demand (ThOD) of 2.20 mg O2/mg test item.

 

The biochemical oxygen demand (BOD) of GUETOL in the test media significantly increased from Exposure Day 6 until test termination after 28 days. The 10-day window started between Exposure Day 5 and 6. At the end of the 10-day window, mean biodegradation of GUETOL amounted to 55 and 56% on Exposure Day 15 and 16, respectively. At the end of the 28‑day exposure period, the mean biodegradation of GUETOL amounted to 63%.Consequently, the test item GUETOL was not readily biodegradable under the test conditions. It was reaching the pass level of 60% at the end of the 28 days, but the 10-day window was not fulfilled.

 

In the toxicity control, containing both GUETOL and the reference item sodium benzoate, GUETOL had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 101 mg/L.

 

In the procedure controls, the reference item sodium benzoate was degraded by an average of 89% 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.

In conclusion, based on results of these two studies, GUETOL was not readily biodegradable under the test conditions, reaching the pass level of 60% at the end of the 28 days, but without fulfilling the 10-day window criterion.