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Toxicity to microorganisms

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Description of key information

 A Respiration Inhibition Test with activated sludge according to OECD Guideline No. 209 (2010) was carried out with the test item Cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, acetone oxime-blocked. Test system was activated sludge of a municipal treatment plant. The test was carried out under static conditions with the limit concentration of 1000 mg/L. The respiration rates of the control, reference and test item replicates were measured after a contact time of three hours by means of oximeter immediately after transferring the solution to the measuring cell and the oxygen depletion was recorded for at least 3 minutes on a flat bed recorder.
The inhibitory effects of the test and reference item were determined in comparison to the control respiration rate. The inhibition of respiration for the test item replicates ranged from -9 to -7 %.
In order to check the activity of the test system and the test conditions a reference test was carried out with copper (II) sulphate pentahydrate as reference item and the reference toxicity was determined. The EC50-value for the reference item was 108 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

The NOEC of the test item Cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, acetone oxime-blocked is 1000 mg/L. The test substance caused no inhibitory effects on activated sludge of a municipal sewage treatment plant at the limit concentration of 1000 mg/L.