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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Biodegradation in water (screening tests): 0% biodegradation in 28 days

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Clarke (2011) is a GLP compliant ready biodegradability, manometric respirometry test conducted according to OECD guideline 301F. A re-inoculation test showed no degradation after 28 days at an initial concentration of 20 mg/L. The study was modified, at the request of the study sponsor, to use soil and activated sludge from a wastewater treatment facility in a composite microbial inoculum. This follows REACH Guidance Chapter R.7b: Endpoint specific guidance, in order to increase the potential for the substance to be biodegraded. Although the study is GLP compliant, the homogeneity, concentration or stability of the test item formulation was not analysed, but this is not believed to have affected the outcome of the study. The study is considered Klimisch 1, reliable without restrictions, and suitable for use as key study for this endpoint. On the basis of this study, ethanethiol is not readily biodegradable.

 

The key data are supported by Thiebaud (1994), a non-GLP, guideline study, according to OECD 301D (Closed Bottle Test), which was reported as the key study in the OECD HPV SIDS Initial Assessment Report for C2-C4 Aliphatic Thiols at SIAM 30 (April 2010). 27% biodegradation was reported in 28 days.. The study is considered Klimisch 2 (reliable with restrictions) and suitable for use for this endpoint. Only the summary of the study is available and therefore the study cannot be fully evaluated.

Van Leerdam (2006) is a published paper. The study is non-GLP, non-guideline but can be considered reliable and suitable for use as supporting information for this endpoint. The study measured the sulphide concentrations in methanol and acetate experiments. The toxicity of ethanethiol and propanethiol was tested by adding them to anaerobic granular sludge that converts methanol, acetate or hydrogen.