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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

The biodegradability under anaerobic and aerobic conditions as well as the elimination are investigated for 2-mercaptoethanol. In an OECD 310 study evaluating the biodegradability in an STP using non-adapted domestic activated sludge, 2-mercaptoethanol was found to biodegrade 69% after 60 days exposure. In an OECD 309 surface water mineralisation study, 2-mercaptoethanol was found to be rapidly eliminated from surface water, with a half-life of 0.079 days.

Based on the results of the OECD 309 study, the substance degrades in the aquatic environment to a level of >70% within a 28 day period and therefore, the substance is considered to be rapidly biodegradable.

Key value for chemical safety assessment

Half-life in freshwater:
0.079 d
at the temperature of:
22 °C

Additional information

The mineralisation of 2-mercaptoethanol in surface water was determined in a GLP-compliant study following OECD guideline 309. Radiolabelled substance was added to surface water at concentrations of 10 and 50 µg/L and incubated for 21 days under aerobic conditions. Samples of the test solutions were analysed to determine the distribution of radioactivity between the surface water and the volatilised radioactivity in the traps, and to identify, where possible, the transformation products.Mineralisation was a significant route of degradation and activity recovered as CO2 increased to more than 60% after 14 days of incubation at both test concentrations. Three major transformation products were detected which exceeded 10% of applied activity at both test concentrations. Transformation product M-1 reached a maximum of 26% after 4 hours (0.17 days) at the low test concentration and a maximum of 13% after 8 hours (0.33 days) at the high test concentration, and then decreased to non-detectable amounts after 6 days of incubation (both concentrations). Transformation product M-3 reached a maximum of 36% (low test concentration) and 30% (high test concentration after 2 days and then decreased to 14% after 9 days of incubation (low test concentration) and to <5% after 14 days of incubation (high test concentration). Transformation product M-6C reached a maximum of 41% (low test concentration) and 39% (high test concentration after 4 hours (0.17 days) and then decreased to non-detectable amounts after 6 days of incubation.It was concluded that 2-mercaptoethanol degrades quickly in water, with a half-life of 0.079 days, and no parent compound was detected in the water layers of both test concentrations after 1 day of incubation.