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Toxicity to microorganisms

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Description of key information

The 3h-EC50 value of ptBP was found to be > 10 mg/L.

Key value for chemical safety assessment

Additional information

The inhibitory concentration of ptBP on the respiration of aerobic waste water bacteria was determined in amixed population of activated sewage sludge (SafePharm, 1991). The test method followed the OECD Guidelines for Testing of Chemicals No. 209. 3,5-Dichlorophenol was used as the reference substance at concentration of 3.2 and 32 mg/L. In this study the oxygen consumption rates were measured after time of 3 hours at concentrations of 10, 100, and 1000 mg/L of the test substance in the range finding study, and 10 mg/L ptBP in the definitive study (3 replicates). The inhibitory concentration (EC50) (3h contact time) for reference substance was 11 mg/L, while the EC50 value (3h contact time) for the test substance was >10 mg/L.

In a similar supporting study the inhibitory concentration of ptBP was determined in an oxygen consumption test with Pseudomonas putida in the presence of nominal concentrations of 125, 250, 500 and 750 mg/L of ptBP for 6 hours (Hüls AG, 1994). A 5% emulsifier concentration (nonylphenol ethoxy propoxylate) was used to obtain sufficient solubility of the test substance. The EC10 (6 h contact time) value for ptBP was determined to be 140 mg/L. No reference substance was used in this study.