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Environmental fate & pathways

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No data on the biodegradation is available for sodium 2 -mercaptoethanolate (target chemical). Read across can however be made to 2- mecaptoethanol (CAS 60-24-2). The (sodium) 2-mercapthoethanolate ion is a conjugated base, the read across substance 2-mercaptoethanol its undissociated acid. With a pKa value of ca. 9.5 for both substances, in an aqueous environment with pH 7, they will be present almost exclusively as 2-mercaptoethanol. Furthermore, as sodium is inorganic degradation does not occur.

2-mercaptoethanol is considered to be rapidly biodegradable as it has shown to quickly degrade in the surface water, with a half-life (DT50) of 0.079 days (1.9 hours) at 50 µg/L. After 1 day of incubation, no parent could be detected in the water layers of both test concentrations. Under biotic conditions, Ethanol, 2-mercapto degraded into the major metabolites, M-1, M-3 (both unidentified) and converted into disulphide M-6C (identified as 2-Hydroxylethyl disulphide). These intermediate compounds degraded to form CO2 (ultimate degradation) in less than 21 days. This result corresponds to a degradation of >70% within 28 days. The test substance is poorly biodegradable under anaerobic conditions.

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