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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 appropriate low concentrations.

Key value for chemical safety assessment

Additional information

There is one valid study according to ISO 8192 available (BASF AG, 1986). Another study conducted by BASF AG, 1991, demonstrates the effect of the test substance on Pseudomonas putida. The ISO guideline study resulted in an EC20 value of >1000 mg/L. However it is not mentioned whether the inoculum (industrial activated sludge) was treated with neutralised or not-neutralised samples. As stated in the guidance document results derived from tests using industrial activated sludge may not be used to extrapolate to domestic sludge.

In the test with Pseudomonas the EC50 value was >1000 mg/L using neutralised samples. Exposure to not neutralised samples resulted in EC10 and EC50 values of 72 and 110 mg/L, respectively. As a worst-case consideration the EC10 value of 72 mg/L was used for the PNECstp derivation.

Two reliable publications are cited in the Beilstein database. Polytox, a blend of 12 streams of aerobic bacteria, was used as inoculum. Nirmalakhandan N et al. (1994) determined a IC50 of 85 mg/L and Prakash J et al. (1996) observed an IC50 of 88 mg/L. There was no statement whether the samples were neutralised or not in both publications.