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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

Growth inhibition test on Tetrahymena pyriformis - 40 hours: EC50=171.4 mg/l
OECD 301C (100 mg/l of PMP, 30 mg/l of activated sludge): 86% degradation in 28 days based on BOD and 99% based on TOC removal. 100 mg/l can be used as a NOEC.

Key value for chemical safety assessment

Additional information

Two data of reliability 2 are referenced for toxicity to microorganisms:

- the first one (Schultz TW, 1997), reports the results of a tetratox test with Tetrahymena pyriformis under static conditions. Based on nominal test material concentration, an 40 hours IGC50 (Inhibitory Growth Concentration) was calculated to be 171.4 mg/L.

- the second one (Ribo and Kaiser, 1983), reports the light emission reduction of the marine bacteria Vibrio fischerii (former Photobacterium phosphoreum) in a microtox test. It led to 30 min EC50= 4.6 mg/L, 15 min EC50= 4.3 mg/L and 5 min EC50= 3.7 mg/L, based on nominal test material concentration.

Only data from ciliate growth inhibition tests, and specially with T. pyriformis, are relevant for the risk assessment for STPs.

The data from the OECD 301C available on the paramethoxyphenol can also be used : since in the conditions of this test, PMP has been demonstrated to be readily biodegradable, the concentration to which PMP has been tested can be used as a NOEC value, ie 100 mg/l.