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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The effect of 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate on the respiration rate of activated sludge was assessed by the method detailed in Directive (EC) 440/2008, Method C.11, ‘Biodegradation - Activated Sludge Respiration Inhibition Test’. Samples of activated sludge (suspended solids 1.6 g/L), fed with synthetic sewage, were exposed to dilutions of the test substance for three hours. The 3-hour EC50 was calculated to be 756 mg/L (95% confidence limits, 482 to 1230 mg/L). The 3-hour EC20 was calculated to be 102 mg/L (95% confidence limits, 37 to 230 mg/L). The EC80 could not be calculated as this was considered above the highest concentration tested, 1000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
756 mg/L

Additional information

The effect of 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate on the respiration rate of activated sludge was assessed by the method detailed in Directive (EC) 440/2008, Method C.11, ‘Biodegradation - Activated Sludge Respiration Inhibition Test’. Samples of activated sludge (suspended solids 1.6 g/L), fed with synthetic sewage, were exposed to dilutions of the test substance for three hours. Their rates of oxygen consumption were determined using an oxygen electrode and were compared with those of controls that contained activated sludge and synthetic sewage alone and were established at the beginning and end of the test. The study employed nominal concentrations of 10, 30, 100, 300 and (triplicate) 1000 mg/L. The reference inhibitor 3,5-dichlorophenol (3,5-DCP) was employed at 3, 10 and 32 mg/L, as a positive control. The specific respiration rate of the control culture established at the end of the test (Control 2, 37.5 mgO2/g/h) was 89% of the rate established at the start (Control 1, 42.3 mgO2/g/h). The three-hour 50% effect concentration (EC50) for 3,5-DCP was calculated to be 9.2 mg/L (95% confidence limits, 6.2 to 13.7 mg/L). These results show that the sample of activated sludge employed was sensitive to inhibition. Concentration-related inhibition of respiration rates were observed at concentrations between 100 and 1000 mg/L, with the highest concentration (1000 mg/L) showing 51 to 53% inhibition. The three-hour EC50 was calculated to be 756 mg/L (95% confidence limits, 482 to 1230 mg/L). The three-hour EC20 was calculated to be 102 mg/L (95% confidence limits, 37 to 230 mg/L). The EC80 could not be calculated as this was considered above the highest concentration tested, 1000 mg/L.