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EC number: 219-702-5
CAS number: 2500-88-1
Preliminary Investigations and Evaluation of Study Design (non-GLP) - Part II
Simulation Study in Surface Water (OECD TG 309)Procedures for the application of the test item to surface water were investigated. A solubility of 1.4 g/L in 1-octanol at 23°C is described. This solvent cannot be used for the application of the test item to surface water because this solvent is not volatile enough. The residual concentration of this solvent, even after careful removal from the test vessels after application, could exceed the test concentration of the test item. 1-Octanol is readily biodegradable and could be preferably degraded and underestimate the biodegradation potential of the test item. Therefore, more suitable organic solvents were tested to verify if an accurate and reproducible application of the test item to surface water is possible.The amount of solvent added to the test solution must be as small as possible (<< 1%) to avoid any adverse effects on the microbial activity. Therefore, a stock solution of 1 g/L (better 10 g/L) is necessary for application. Acetone, methanol, ethanol and acetonitrile were considered as suitable solvents. Solubility data for methanol (provided by the sponsor) indicated that the solubility is for too low to prepare a suitable stock solution. The solubility in acetone, acetonitrile and ethanol was investigated at a concentration of 5 g/L. The test item was not soluble in any of these solvents. Even after up to 7 days agitation on a shaker, the test item was present as fine powder. It was concluded that the test item is highly insoluble and therefore OECD TG 309 is not feasible to conduct.
Alternative TestingOther Simulation StudiesStudies according to OECD TG 308 or OECD TG 307 are described in the decision as alternative simulation studies when a study according to OECD TG 309 is not possible. However, these simulation studies are also not technically feasible, as it is not possible to prepare an adequate application solution.
Enhanced Test OECD TG 310Therefore, an enhanced OECD TG 310 test in combination with LC-HRMS (high resolution mass spectrometry) analysis for detection and identification of metabolites was performed. This test simplifies the detection and identification of metabolites due to the higher test concentration. Previous studies (301F over 28 and 60 days) showed an incomplete mineralization of the test item. These results let assume that metabolites of the primary biodegradation pathway should be still present in the test solutions and that this approach should be suitable to get knowledge about the chemical structures of the metabolites.
According to a Compliance Check of ECHA, the identification of degradation products was required. The OECD TG 309 was recommended as the preferred test, if technically feasible.
Based on experiments demonstrating very low water solubility and likewise low solubility in other solvents, it was concluded that the test item is very poorly soluble and therefore OECD TG 309 is not feasible.Therefore, an enhanced OECD TG 310 test in combination with LC-HRMS (high resolution mass spectrometry) analysis for detection and identification of metabolites was performed.
Metabolites were investigated and mineralisation of the test item was determined in an enhanced screening test with a non-adapted activated sludge over a test period of 62 days in the Headspace Test. The study was conducted from 2021-11-23 to 2022-01-27, following OECD 310 at the test facility. The test item was tested at a concentration of 27.1 mg/L in duplicates (test end: 5 replicates), corresponding to a carbon content of 20 mg C/L.Investigations about metabolites were done by LC-HRMS analysis. The mineralisation of the test item was followed by TIC analyses of the quantity of CO2 produced by the respiration of bacteria. The amount of TIC produced was calculated by correcting the results of the test and reference item for endogenous TIC production of the control groups and the blind value of the sodium hydroxide solution. The biodegradation was calculated for each sampling time.To check the activity of the test system sodium benzoate was used as functional control. The percentage degradation of the functional control reached the pass level of 60 % within 10 days and came to a maximum of 92 % on day 16. The 95 % confidence interval on day 28 was 84 – 96 %.The test item replicates reached the 10% level (beginning of biodegradation) within 10 days. The biodegradation on day 28 was 20 % and reached 48 % until test end (day 62). The 95 % confidence interval on day 62 was 30 – 66 %.A plateau phase did not appear to have been reached after 62 days, and one replicate even reached 70% degradation after 62 days. This reinforces the assumption that the substance would be degraded even further.
The validity criteria according to the guideline are fulfilled.No metabolites were detected. Putatively, the alkyl chains of the test item can be completely mineralised. But, higher mineralisation of the test item will be very slow due to the low water solubility of the test item linked to a limited bioavailability.
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