Registration Dossier

Ecotoxicological information

Toxicity to soil microorganisms

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

2-mercaptoethanol has a 28 day EC50 of >1000 mg/kg soil dw and a 28 day EC10 of 330 mg/kg soil dw. However, transfer to the soil compartment is not expected.

Key value for chemical safety assessment

Short-term EC50 for soil microorganisms:
1 000 mg/kg soil dw
Long-term EC10 or NOEC for soil microorganisms:
330 mg/kg soil dw

Additional information

In a 28-day GLP test with natural soil according to OECD TG 216, the nitrogen transformation of 2-mercaptoethanol was investigated. Statistical evaluation of the endpoint nitrate formation revealed an EC50 (28-day) of > 1000 mg/kg soil dw and an EC10 (28-day) of 330 mg/kg soil dw, related to the nominal concentrations.

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 to be 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. 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.