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Toxicity to microorganisms

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Description of key information

The 3 hour EC50 of 2-amino-6-chloro-4-nitrophenol for inhibition of respiration rate of activated sludge was 281.5 mg/L, based on nominal concentration of test substance.

Key value for chemical safety assessment

EC50 for microorganisms:
281.5 mg/L

Additional information

An activated sludge respiration inhibition test, following OECD 209 guideline and GLP, was conducted on 2-amino-6-chloro-4-nitrophenol.

Inoculum was activated sludge collected from the aeration tank of the Company's sewage treatment plant, receiving predominantly domestic sewage.

The respiration inhibition of sludge microorganisms exposed to the test item was determined after 3 hour incubation time under static conditions. The percentage of inhibition of sludge respiration was 0, 14.7, 22.5, 27.1, 22.5 and 53.5 induced by the test item concentrations of 0, 1.43, 4.60, 14.6, 46.9 and 150 mg/L, respectively. The calculated EC50 for total respiration of activated sludge was 281.7 mg/L expressed as nominal concentration.

A concentration dependent inhibition of respiration was seen with 3,5-dichlorophenol and the calculated EC50 was 25.5 mg/L. The EC50 of thereference substance was between 5 and 30 mg/L and satisfied the validity criterion.

The results of this study indicate that the test item has no marked adverse effect on the respiration of activated sludge, under the reported experimental conditions.

This activated sludge, respiration inhibition test is classified as acceptable, and satisfies the guideline requirements for the OECD 209.