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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The 3-hour NOEC (EC10) of the test item to activated sludge microorganisms was at least 1000 mg/L (i.e. the saturation concentration of the test item). This value might even be higher but concentrations above 1000 mg/L were not tested. The 3-hour EC20, EC50, and EC80 could not be calculated but were clearly higher than 1000 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

The inhibitory effect of the test item Tert-butyl-4-methoxy-4’-dibenzoylmethane on the respiration rate of aerobic wastewater microorganisms of activated sludge was investigated in a 3-hour respiration inhibition test according to OECD Guideline 209 and EU Commission Directive 88/302/EEC, Part C.11. Based on the EU testing guidelines, a limit test with a nominal test concentration of 1000 mg/L was performed. In addition, two controls and three different concentrations of the reference item 3,5-dichlorophenol (5, 16, and 50 mg/L) were tested in parallel. The results of these treatments confirmed suitability of the activated sludge and the method used. At the test item concentration of 1000 mg/L, the test item was not completely dissolved in the test medium. Thus, the test concentration was clearly above the water solubility limit of Tert-butyl-4-methoxy-4’-dibenzoylmethane under the test conditions. The test item had no inhibitory effect on the respiration rate of activated sludge after the incubation period of three hours at a loading rate of 1000 mg/L. The saturation concentration (water solubility limit of Tert-butyl-4-methoxy-4’-dibenzoylmethane under the test conditions) was reached and no inhibitory effect was determined after three hours contact time. Thus, the 3-hour NOEC (EC10) of the test item to activated sludge microorganisms was at least 1000 mg/L (i.e. the saturation concentration of the test item). This value might even be higher but concentrations above 1000 mg/L were not tested. The 3-hour EC20, EC50, and EC80 could not be calculated but were clearly higher than 1000 mg/L.