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Environmental fate & pathways

Phototransformation in water

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Description of key information

Photolysis in water is expected to contribute significantly to the overall degradation of disulfiram (analogue substance experimental half-lives < 10 hours) in aquatic systems.

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Additional information

No data on photodegradation of disulfiram in water are available. Therefore, a conclusion had to be drawn based on data from an analogue substance. The photolytic degradation in water of tetramethylthiuram disulfide (CAS No. 137-26-8) was investigated in two studies (Norris, 1990 and Knoch, 1994). The first test (Norris, 1990) was carried out according to EPA’s Pesticide Assessment Guidelines, Series 161-2, Photodegradation Studies in Water (1988), under GLP conditions. A14C-thiramsolution (test concentration = 8.9 mg/L) was exposed to natural sunlight at 25°C. The results showed a rapid photodegradation of the test compound, with a half-life of 8.8 hours (being CS2 the major degradation product). The second test (Knoch, 1994) was conducted according to OECD Guideline draft: Phototransformation of Chemicals in Water – Direct and Indirect Photolysis (2007), under GLP conditions. A14C-thiram solution (test concentration = 10.25 mg/L) was exposed to artificial light (xenon lamp) at 25°C. The resulting predicted half-life was 4.1 hours.