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Environmental fate & pathways

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After evaporation or exposure to the air, 2-mercaptoethanol will be rapidly degraded by photochemical processes with OH-radicals. Due to the structural properties, hydrolysis is not expected to be an important fate path. In water, 2-mercaptoethanol will be degraded by indirect photodegradation with OH radicals within 4.7 to 393 days, depending on the concentration of the OH radicals. Testing of the stability in water was performed by Stevens et al (1983). This study is given in detail in IUCLID chapter 5.6. The stability was investigated with the test substance dissolved in 0.1 M potassium chloride buffer with initial concentrations ranging between 0.5 and 1.0 mM. It was found that the half-life of 2-mercaptoethanol is influenced by pH and temperature. With increasing pH and temperature the degradation increases too. At pH 8.5 and 20°C a half-life of 4 h was measured while at the same pH and 40°C a half-life of 1h was found. The chemical mechanism as well as the products of degradation were not examined in this study. According to the OECD QSAR Application Toolbox v1.0 2-mercaptoethanol forms disulfide bonds due to its mode of action (disulfide formation). In a biodegradation test performed by Japanese MITI Institute 2-hydroxyethyldisulfide (CAS 1892-29-1) was formed under the given test conditions (MITI 1992) (for further information see IUCLID chapter 5.2.1). Therefore, it can be assumed, that 2-hydroxyethyldisulfide (CAS 1892-29-1) is the main product of abiotic degradation.