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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

Disulfiram is not expected to be persistent in aquatic environments (DT50 < 2 days).

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No data on the biodegradation of disulfiram (CAS No. 97-77-8) in water and sediment were available. Therefore, a conclusion based on data from an analogue substance had to be drawn. Biodegradation in water/sediment systems of tetramethylthiuram disulfide (CAS No.137-26-8), substance structurally and composition related to tetraethylthiuram disulfide, was investigated in two studies.

These tests were conducted according to the German BBA Guidelines, Part IV, Section 5-1 (1990): “Degradability and metabolism of Plant Protection Products in Water/Sediment Systems”, under GLP conditions. A concentration of 1.195 mg14C-thiram/L water of the radiolabelled compound was incubated in the first study (1992) for 101 days.14C-thiram was very rapidly degraded, mainly to14CS2,14CO2and at least 20 minor metabolites, which were further degraded to CO2, other small fractions and disappeared by adsorption to sediment. The half life of the compound was 1.9 days. The non-extractable radioactivity was there further degraded and mineralised. In the second study (1995), 16.26 ug/L a.i. were incubated for 10 days under similar conditions, resulting in a rapid degradation (half life= 0.7 days) leading to several minor metabolites that further mineralised, being CO2the main degradation product.