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Toxicity to microorganisms

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Description of key information

Key study,guideline OECD 209, K2:

NOEC (3h)= 1000 mg/L

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

The effects of Amitrole on the respiration rate of microorganisms contained in activated sludge after a contact of 3 h was assessed in accordance with OECD guideline 209, "Activated sludge, respiration inhibition test" (1984).

Amitrole was tested at concentrations of 1000, 316, 100, 31.6 and 10 mg/L. There was no decrease in oxygen consumption observed in any of the concentrations tested. The 3h EC50can therefore be concluded to be above 1000 mg/L. The reference material 3.5 -dichlorophenol was tested at concentrations of 30, 15 and 5 mg/L. The 3h EC20, EC50and EC80vlaues were calculated to be 6.3, 10.7, and 18.0 mg/L respectively.

The respiration rates for the 2 control vessels were within 15% of each other, and the EC50 of the reference material was in the range 5 to 30 mg/L, meeting the criteria for a valid test.