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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Endpoint:
biodegradation in water: sediment simulation testing
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
other:
Justification for type of information:
According to REACH Annex XI column 2, “9.2. Further biotic degradation testing shall be proposed by the registrant if the chemical safety assessment according to Annex I indicates the need to investigate further the degradation of the substance and its degradation products. The choice of the appropriate test(s) depends on the results of the chemical safety assessment and may include simulation testing in appropriate media (e.g. water, sediment or soil).”

The 'ready' biodegradability of the test item was investigated in the Manometric Respirometry Test, according to OECD Guideline 301 F, EC 440/2008 C.4 -D, and GLP principles. A nominal test concentration of 50 mg O2/L ThOD was used. There was no oxygen consumption and no biodegradation in two replicates after 28 days, 0% degradation was stated.
In the available hydrolysis study according to OECD 111, the substance was determined to be hydrolytically unstable under acidic, neutral and basic conditions, the rate of the reaction increasing with increase in pH. A DT50 value of 12 hours was obtained at pH 4, 2 hours at pH 7 and a DT50 value of less than 5 minutes was obtained at pH 9.
N-Phenyl imide was identified via EpiSuite estimation as the potentially hydrolysable group, no further hydrolysable groups were identified.
So it can be concluded, that the substance is hydrolytically unstable, but not biodegradable, which also applies to potential hydrolysis products. This is proven by the biodegradation test of the actually registered substance, in combination with the short hydrolysis half-life of 2h at neutral pH.

With regard to sediment, although the substance is not likely to undergo significant biotic biodegradation in the environment, it is likely to have a high mobility. A Soil Adsorption Study performed by HPLC method calculated a soil adsorption coefficient, Koc of 970 (log Koc= 3.0). On this basis the substance would not be expected to adsorb onto sediment.
According to REACH Annex IX column 1, Sediment simulation testing is required for substances with a high potential for adsorption to sediment, which is not the case here and testing can hence be omitted.
In consequence it can reasonably be assumed that further testing, e.g. Aerobic mineralisation in surface water - simulation biodegradation test (test method: EU C.25./OECD TG 309) would result in no or not relevant additional degradation, and testing can be omitted as no further relevant results could be obtained.

Data source

Materials and methods

Results and discussion

Transformation products:
not specified

Applicant's summary and conclusion