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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

Diefenbach (1999) provided EC50 (respiration) of 950 mg/L

Key value for chemical safety assessment

EC50 for microorganisms:
950 mg/L

Additional information

A reliable study of common sewage activated sludge microorganism exposed to nonylphenol was reported by Diefenbach (1999). The test organisms represented a mixture of microorganisms contained in common activated sludge treatment of wastewater and effects concentration reported as EC50 was based on percent inhibition of respiration. The mixture of microorganisms was exposed to nominal concentrations 125, 251.6, 500, 1000, and 2002 mg nonylphenol/L under static conditions. An EC50 was estimated at 950 mg nonylphenol/L as the maximum percent inhibition after 3 hrs exposure was 44% and a 50% inhibition level was not attained. The authors concluded total inhibition of activated sludge respiration could not be expected due to the limited water solubility of nonylphenol.