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Environmental fate & pathways

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Based on calculations according to AOPWIN v1.92 the substance is indirectly photodegraded by reaction with hydroxyl radicals in the atmosphere with a half-life of less the 1 hour.

Three studies on the hydrolysis in the category of derivatives of 4,4’-bis(1,3,5-triazinyl-2-yl)amino)stilbene-2,2’-disulfonic acid, each with one anilino and one alkyl amino moiety,are available. All studies (for EC 432-690-8, EC 476 -900 -6, and EC 416 -640 -2) demonstrate that the test substances are stable (hydrolysis < 10 %) at pH 4, 7 and 9 at 50 °C and that the half life of the tested substances for hydrolysis is proved to be greater than 1 year. Therefore, it is assumed that the substance defined in section 1 is hydrolytically stable in water as well.

In dilute solutions and in presence of sunlight, the substance undergoes reversible isomerization of the stilbene moiety. In this process, two isomeric forms occur. The E- and Z-isomers are under environmental conditions in equilibrium within a few minutes. The parent substances used as fluorescent whitening agent consist of the E-isomer, while isomerization to the Z-form leads to complete loss of fluorescence. The studies for the analogue CAS 16470-24-9 demonstrate that at solar latitude 60°, at 25°C, and on surface layer depths of 0 to 5m the remaining E-isomer fraction is 17.8 to 13.3, respectively. The preceding isomer equilibrium influences the photo-degradation rate. The half-life for photo-oxidation in natural water was measured for the same substance and under the same light conditions on the surface layer: 313 min (CAS 16470-24-9). The experimental kinetic data are used to calculate photochemical half-lives as a function of surface layer depth, optical density of the water, and time of the year.

Although there are no data available concerning ready biodegradability, the substance is very unlikely to be readily biodegradable. Studies on the biodegradability in water of three members of the category of derivatives of 4,4’-bis(1,3,5-triazinyl-2-yl)amino)stilbene-2,2’-disulfonic acid, each with one anilino and one alkyl amino moiety, are available. All studies (for EC 432-690-8, EC 476 -900 -6, and EC 416 -640 -2) demonstrate that the test substances are not readily biodegradable in the available studies. Therefore, the substance defined in secction 1 is considered non readily biodegradable.

No data on the biodegradation in sediments and surface water are available for the test item. However, further biotic degradation testing shall be proposed if the chemical safety assessment according to Annex I indicates the need to investigate further degradation of the substance and its degradation products. By read-across the substance was found to be non-biodegradable in studies concerning ready biodegradability as well as BOD5. It is assumed that the test substance is not biodegradable in simulation tests either. Therefore, simulation studies on surface water and sediments are not provided.