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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The inhibition of the degradation activity of activated sludge is not anticipated when introduced in appropriately low concentrations.

Key value for chemical safety assessment

EC50 for microorganisms:
100 mg/L

Additional information

A weight of evidence approach was used to assess toxicity of 1-Methyl-2-pyrrolidone (NMP, CAS 872-50-4) to microorganisms:

- A literature study performed according to national Polish guidelines is available (Gomolka et al., 1981). In several tests with changing test parameters, different levels of respiration inhibition were found depending on the concentration of the substance and the status of adaption of the inoculum. At a prolonged onflow of NMP to a sewage treatment plant employing non-adapted sludge the NMP concentration in the wastewater shall not be higher 100 mg/L (similiar to an EC10).

- In a further test performed according to ISO 8192, using activated sludge from the BASF STP which might be pre-adapted to NMP, an EC50 (30 min) > 600 mg/L was found (BASF AG, 1987).


Both studies indicate the substance to not exhibit an inhibitory effect on the degradation activity of activated sludge at a test concentration of 100 mg/L.

Additionally, the key study on ready biodegradability according to OECD guideline 301C used a concentration of the test substance of 100 mg/L without an inhibitory effect (= comparable to NOEC) while the substance is readily biodegradable (see chapter 4.1.2).


Therefore, 1-Methyl-2-pyrrolidone (NMP, CAS 872-50-4) is assessed to not inhibit the degradation activity of activated sludge when introduced in appropriately low concnetrations.