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Environmental fate & pathways

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The test substance is a solid with very low vapour pressure, very high solubility and low Kow. It was estimated as hydrolytically stable at pH 4, 7 and 9 at 50 °C and it has an estimated half-life period longer than one year at 25 °C at pH 4, 7 and 9. The substance has not hydrolysable chemical groups in the chemical structure.

Based on calculations according to AOPWIN v1.92, the substance is indirectly photodegraded by reaction with hydroxyl radicals in the atmosphere with half-lives of about 0.4 hours taking into account a 12-h day and a mean OH radical concentration of 1.5E06 radicals per cm³.

The substance is a member of the Stilbene Fluorescent Whitening Agents category and, based on the data on analogous substances in the category, it is estimated to undergo direct photodegradation in surface waters, with half-lives ranging from about to 4 to 5 hours in the photic zone of lakes and rivers. Field measurements combined with mathematical modelling of sedimentation and photolysis show that direct photolysis is the only pathway of degradation and effective throughout the aquatic zone due to the dynamics of rivers and layers in lakes. There is no indication of biodegradability.

Adsorption will partially bring the substance onto the surface of suspended particles and will also contribute to the adsorption of the substance into sediments, where an anaerobic degradation process can be effective. Nevertheless this is unlikely to occur in the usual conditions of use, where the substance is adsorbed to the sludge in the STP, therefore significant release into surface waters is not expected and exposure of sediment is thereby unlikely.

The substance is estimated as not bioaccumulative, based on the log Kow and the testing results on similar substances in the category.