Registration Dossier
Registration Dossier
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EC number: 609-336-8 | CAS number: 371756-75-1
Endpoint summary
Administrative data
Description of key information
Additional information
Based on calculations according to AOPWIN v1.92, the substance is indirectly photodegraded by reaction with hydroxyl radicals in the atmosphere with half-lifes ranging of about 0.6 hours, taking into account a 12-h day and a mean OH radical concentration of 1.5 E6 radicals per cm³.
Two studies on the hydrolysis of the substances in the stilbene fluorescent whitening agents are available. Both studies (for CAS 16090-02-1 and CAS 16470-24-9) 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 (CIBA-GEIGY 1992).
Therefore, reading across, it is assumed that the subtsance CAS 371756 -75 -1 is stable in water as well.
In dilute solutions and in presence of sunlight, the substances in the stilbene fluorescent whitening agent category undergo 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. Two studies (for CAS 16090-02-1 and 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 13.9 to 9.5 and 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 substances and under the same light conditions on the surface layer: 278 min (CAS 16090-02-1) and 313 min (CAS 16470-24-9). Based on measured kinetic parameters and the quatum yield, photochemical half-lives in three Swiss lakes are calculated according to GCSOLAR as a function of surface layer depth and time of the year (Kramer, 1996). Both substances degrade with nearly identical half-lives. Therefore, reading across, it is assumed that this substance follows the same photolytical processes and is effectively degraded in surface waters.
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