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Ecotoxicological information

Toxicity to soil macroorganisms except arthropods

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Description of key information

2-mercaptoethanol has a 14 d LC50 of 908 mg/kg soil dw. However, transfer to the soil compartment is not expected.

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil macroorganisms:
908 mg/kg soil dw

Additional information

In a 14-day GLP test with artificial soil according to OECD TG 207, the acute toxicity of 2-mercaptoethanol to the earthworm Eisenia fetida was investigated. Statistical evaluation of the endpoint mortality revealed a 14-day LC50 of 908 mg/kg soil dw, based on nominal concentrations.

The available data for 2-mercaptoethanol do not indicate a potential for high adsorption or high persistence in the soil but do indicate that the substance is very toxic to aquatic organisms. Based on the results of the OECD 309 study, 2-mercaptoethanol degrades in the aquatic environment to a level of >70% within a 28 day period and therefore, the substance is considered rapidly biodegradable. Also, as the logKoc and LogPow are below 3 and no cationic and surface active properties are given, a low adsorption potential is indicated and therefore, transfer to the soil compartment is not expected. However, aquatic ecotoxicity tests showed Daphnia magna were the most sensitive species revealing a 48 hour EC50 of 0.4 mg/L and a 21 day NOEC of 0.0632 mg/L and thus, 2-mercaptoethanol is considered acutely and chronically very toxic for aquatic organisms.

On the basis of the available data, 2-mercaptoethanol would meet the criteria for soil hazard category 2 and, as such, confirmatory short-term soil toxicity tests were conducted on terrestrial invertebrates (earthworms) and terrestrial micro-organisms. As the initial risk assessment using equilibrium partitioning for the soil compartment and the updated risk assessment using the terrestrial toxicity data did not indicate risk, no further toxicity testing on soil organisms is considered necessary and the Annex IX and X higher tier tests on soil organisms have been waived.