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Toxicity to microorganisms

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Description of key information

3 hour EC50 (activated sludge): 1174 mg/L

Key value for chemical safety assessment

EC50 for microorganisms:
1 174 mg/L

Additional information

In the key study from the NOACH laboratory, the respiration inhibition of Chloracetamid (which contains > 98% a.i.) to activated domestic sludge obtained from the municipal treatment plant of 31137 Hildesheim, Germany was determined in a GLP test following OECD testguideline 209. Two deviations to the guideline were observed: The sludge was washed and diluted with autoclaved tap water to 3.0 +/- 0.6 g dry sludge/L instead of 4.0 g dry sludge /L as described in the test guideline. Furthermore, another reference substnace was used. These deviations are considered to be not major deviations to the guideline which would affect the reliability of the obtained results. Based on the good documentation and the general compliance with the test guideline, the study is scored as Klimisch 2.

The nominal test concentrations were 0 (control, two replicates), 111, 333, 1000, 3000 and 9000 mg Chloracetamid/L. From each treated test solution, one replicate was set up. Dose verification analysis was not performed. The oxygen consumption was measured for at least 3 minutes after 3 hours incubation. The temperature ranged from 18 to 22 °C. The oxygen consumption in the controls varied by < 15% and hence this validity criterion is fulfilled. The EC50was calculated as 1174 mg Chloracetamid/L (95% C.I.: 828-1664 mg/L). The EC20and EC80values were 141 and > 9000 mg Chloracetamid/L.

This study is considered to be acceptable for the risk assessment.

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