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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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For the test substance studies on the ready and inherently biodegradability according to OECD TG 301 F (Currenta 2009) and OECD TG 302 C (Currenta 2010), respectively, were conducted. In the ready biodegradability test the substance showed a degradation of 47 % after 28 days, indicating a basic biodegradability. In the inherent biodegradability test the substance showed a degradation of 78 % after 28 days leading to the conclusion, that the substance is inherently biodegradable. Based on those results it is considered that the test substance might not fulfil the criteria for persistency.
Moreover, the substance is poorly soluble, therefore adjusting according to Annex III (OECD TG 301) is advisable when performing an OECD 301 study.
Repeating the test according to OECD 301 D (Closed Bottle) instead of 301 F is recommended, as OECD 301 D is carried out within the range of the water solubility of the substance (2 - 5 mg/L).
A repetition of the previously conducted OECD 301 F will likely result in an improved degradation rate and a possible declaration as "readily biodegradable" due to the constant adaption of the inoculum of the wastewater treatment plant. Since this has direct implications on the PBT assessment of the substance, these measures are considered the best mode of action by the registrant.
Therefore, the registrant considers creating new data on the ready biodegradability of the substance, which is expected to provide sufficient and conclusive information on the biodegradability behavior. The necessity for simulation studies will be reevaluated based on the results.

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