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Environmental fate & pathways

Phototransformation in air

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Description of key information

The half-life for phototransformation in air of 24 hours will be used in the present assessment.

Key value for chemical safety assessment

Additional information

The following text was copied from the EU Risk Assessment Report (2003), pg. 30: "In polluted urban air half-lives of few hours have been reported (Sakugawa et al. 1990). No clear figures of overall photolysis rates have been presented in the literature. A study done by Olzyna (1988) in Whitetop Mountain indicates that in unpolluted air at night time (during 8-10 hours) indirect photolytic degradation decreases H2O2 levels by about 25% and consequently 50% decrease would take 16-20 hours (it is assumed that the night time production rate of H2O2 is low or negligible). In polluted air diurnal variations in concentrations seem to be more or less larger than in unpolluted air. According to the existing test data from different atmospheric conditions (Olszyna 1988, Sakugawa et al. 1990, Kleinman 1986) a half-life of 24 hours (rate constant of 0.029 h-1) will be chosen to represent the average degradation half-life in the atmosphere."