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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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In accordance with REACH Annex IX the study 9.2.1.4 Sediment Simulation Testing only has to be proposed by the registrant if the substance has a high potential for adsorption to sediment. Furthermore according to REACH column 2 Annex IX, the study need not be conducted if direct or indirect exposure of the sediment is unlikely. 
Due to its physico-chemical properties (high water solubility, hydrophilic, low octanol-water partition coefficient of -0.88) Acetoguanamine will not adsorb to soil or sediment organic matter fractions. As such, there is no potential for exposure of sediment, even in the event of direct release of Acetoguanamine to aqueous system Acetoguanamine will stay in the aqueous phase. Therefore no sediment simulation testing is required.
It is scientifically unjustified to perform a Simulation Biodegradation Test in Surface Water with Acetoguanamine.
For the test substance Acetoguanamine it is not expected to observe any signs of degradation in this test. In a screening test according to OECD Guideline 301E ("Ready Biodegradability: Modified OECD Screening Test") no biodegradability (no DOC removal at all within 48 days) was found for Acetoguanamine. Without biodegradation the result of the Simulation Test in Surface Water would show similar results of a hydrolysis test. Also in the test according to OECD 111 ("Hydrolysis as a function of pH") not any signs of hydrolysis were observed.
Furthermore the result of the required test only has an impact if a Risk Assessment has to be performed. The result serves for the correction of the PEC if the test substance degrades slower or quicker than the standard value predicts. For Acetoguanamine it is not necessary to perform a risk assessment because the substance was not identified as hazardous. Therefore a Simulation Biodegradation Test in Surface Water is scientifically unjustified because it would not lead to any new information on the hazard of Acetoguanamine

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