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Environmental fate & pathways

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Description of key information

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Concerning the stability of Ethylhexyl Methoxycinnamate, one study on hydrolysis and one study on phototransformation in water are available. As a consequence, these studies were chosen as key studies.

The study on hydrolysis as a function of pH consisted of two separate tests, the first test was under flow-through conditions, the second one in a closed system. This second closed system test was performed because the results with the flow-through test were unsatisfactory. The half-life (hydrolysis) of Ethylhexyl Methoxycinnamate was found to be > 1 year at pH's 4, 7 and 9 at 20°C. The degradation products that were formed could not be succesfully identified, as both TLC methods (straight phase and reversed phase) did not confirm each other.

In the study examining the phototransformation in water, it was concluded that according to the classification scheme by Mensink, trans-2-Ethylhexyl 4-methoxycinnamate can be regarded as being very rapidly degradable when transition to cis-2-Ethylhexyl 4-methoxycinnamate is taken into account. When trans-cis transition is left out, 2-Ethylhexyl 4-methoxycinnamate can be classified as fairly degradable with a DT50 in the range of ca. 5-9 days. The main photolytic degradation products are p-methoxycinnamate (34.8% applied initial substance), unidentifiable substances M1 and M3 (according to TLC method I) or MA, MB and MD (according to TLC method II). The quantum yield for the trans-to-cis conversion was 0.0021. The quantum yield for the degradation into metabolites appeared to be in the range of 1*10^-5 to 2*10^-5.

It is concluded that hydrolysis is not a relevant degradation process, whereas the test substance is fairly degradable by phototransformation in water.