Registration Dossier
Registration Dossier
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EC number: 220-618-6 | CAS number: 2835-95-2
Toxicity to microorganisms
Administrative data
Link to relevant study record(s)
Description of key information
The 3 hour EC50 value of 5-amino-o-cresol to micro-organisms was 17.6 mg/L for nitrification rate and >150 mg/L for heterotrophic respiration and total respiration inhibition. based on nominal test concentrations. The EC50 total respiration > 150 mg/L is considered as the most reliable value which integrates the effect of the 5 -amino-o-cresol on the functionning of all organisms in a STP.
Key value for chemical safety assessment
- EC50 for microorganisms:
- 150 mg/L
Additional information
An activated sludge respiration inhibition test, following OECD 209 guideline and the GLP, was conducted on 5 -amino-o-cresol. The inoculum was non-adapted activated sludge collected from the sludge return line at Burley Menston Sewage Treatment Works (West Yorkshire, U.K.) which has a predominantly domestic catchment.
A range-finding test was conducted at 1, 10, 100 and 1000 mg/L in order to establish suitable test concentrations for the definitive test. Significant inhibition was observed at all endpoints between 10 - 1000 mg/L concentration. For this reason, a full definitive test for total, heterotrophic and nitrification respiration was conducted.
The respiration inhibition of sludge micro-organisms was determined after 3 hour incubation time at nominal concentration of 0, 0.24, 1.2, 6 and 150 mg/L.
For total respiration inhibition, statistical significance was observed at 6 and 150 mg/L. A conservative NOEC of 1.2 mg/L was derived despite the lack of statistical significance at 30 mg/L. For heterotrophic inhibition, statistical significance was observed at 150 mg/L and no significant inhibition was observed at a lower level. Hence, the NOEC for heterotrophic respiration was derived to be 30 mg/L. For inhibition of nitrification respiration, statistical significance was observed at 6 and 150 mg/L. The NOEC for nitrification respiration was 1.2 mg/L.
The EC50 value for nitrification respiration, heterotopic respiration and total respiration of the reference substance was 1.198 mg/L, 10.73 mg/L and 7.718 mg/L, respectively. This satisfied the validity criterion for the EC50 values of the reference substance.
In conclusion, the 3-hour EC50 value of 5 -amino-o-cresol to microorganisms was 17.6 mg/L for nitrification rate and >150 mg/L for heterotrophic respiration and total respiration inhibition, based on nominal test concentrations. The EC50 total respiration > 150 mg/L is considered as the most reliable value which integrates the effect of the 5 -amino-o-cresol on the functionning of all organisms in a STP.
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