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Diss Factsheets

Environmental fate & pathways

Phototransformation in water

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Administrative data

Link to relevant study record(s)

Description of key information

Half life, 20.73 days, EPA 161-2, Sparrow (2001)
Half life, 15.88 days, EPA 161-2, Anderson (2001)
Half life, 13.98 days, EPA 161-2, Schwartz (1999)
Half life, 17 days, EPA 161-2, Dixon (1999)

Key value for chemical safety assessment

Half-life in water:
20.73 d

Additional information

The effect of phototransformation in aqueous solution has been determined in four studies, provided as a weight of evidence to address this endpoint.

All four studies were performed under similar conditions. The test material was applied at a dose rate of approximately 10 ppm and incubated at 25ºC for between 30 and 32 days. Samples were irradiated for 12 hours per day at an intensity based on 75% of the measured peak intensity of natural sunlight. Sparrow (2001) and Anderson (2001) were performed using sterile lake water as the test medium, whereas Schwartz (1999) and Dixon (1999) used pH 7 sodium phosphate buffered solution.


All four studies were performed according to GLP, in line with standardised guidelines, with a high standard of reporting and have thus been assigned a reliability score of 1 in line with the principles for assessing data quality set out by Klimisch (1997).


The consensus is that photolytic degradation only slightly increases the rate of degradation. The half lives and degradation patterns produced in both irradiated and non-irradiated samples are very similar, thus it can be concluded that the major pathway for degradation is hydrolysis and not photolysis. The available data are considered to be complete and the half life has been reported based on the worst case, at 20.73 days.