Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Ready biodegradation data are available for ethanethiol from a GLP-compliant manometric respirometry test conducted in accordance with OECD guideline 301F (Clark, 2011). An initial test showed no biodegradation after 28 days at an initial concentration of 50 mg ethanethiol/L. 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 study for the biodegradation of ethanethiol in water is supported by Van Leerdam (2006). This is a published paper, which measured the sulphide produced when ethanethiol was added to anaerobic granular sludge and converted methanol, acetate or hydrogen. This is also supported by the key study included in the OECD HPV SIDS Initial Assessment Report for C2-C4 Aliphatic Thiols at SIAM 30 (April 2010) (Thiebaud 1994), which is a non-GLP study following OECD guideline 301D (Closed Bottle Test), in which 27% degradation was reported in 28 days. However, only the summary of this study is available and therefore it cannot be fully evaluated.

Results from these supporting studies also indicate that ethanethiol is not readily biodegradable in water.

No data are available for the biodegradation of ethanethiol in soil or water and sediment. The result of the Chemical Safety Assessment indicates that further testing of biodegradation is not necessary.