Registration Dossier

Ecotoxicological information

Toxicity to microorganisms

Currently viewing:

Administrative data

Link to relevant study record(s)

toxicity to microorganisms, other
Tetrahymena pyriformis
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
no guideline followed
Principles of method if other than guideline:
Test procedure according to T.W. Schultz (1993) Aquatic toxicology of nitrogen heterocyclic molecules: Quantitative structure-activity relationship, in J.O. Nriagu, (Ed.) Aquatic Toxicology, Wiley, New York, 1983, 579-612.
GLP compliance:
Specific details on test material used for the study:
purchased from commercial sources (Aldrich Chemical Co., Milwaukee, WI, U.S.A. or Pfaltz and Bauer Inc., Sanford, CT, U.S.A.) and not repurified.
Analytical monitoring:
dimethylsulfoxide (DMSO)
Details on test solutions:
Due to solubility and toxicity differences, stock solutions of the individual test compounds were prepared in dimethylsulfoxide (DMSO) at a number of concentrations: 5000,
10000, 25000, or 50000 mg/L. In all cases the amount of stock solution added to the cultures was less than 0.75%. Such levels have no effect on Tetrahymena growth.
Test organisms (species):
Tetrahymena pyriformis
Details on inoculum:
Axenic cultures used.
Test type:
not specified
Water media type:
Limit test:
Total exposure duration:
60 h
Nominal and measured concentrations:
5 concentrations tested and a control
Details on test conditions:
- Cell-population levels were estimated spectrophotometrically
- Assayed in duplicate for a minimum of 3 replicates.
Reference substance (positive control):
not specified
60 h
Dose descriptor:
Effect conc.:
119.62 mg/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Remarks on result:
other: 95% CL: 99.57 - 155.38 mg/L
Reported statistics and error estimates:
Biological response was determined using probit analysis in the Statistical Analysis System software. In this analysis, Y equaled the % control absorbance and X equaled the concentration of toxicant in mg/L.
Validity criteria fulfilled:
not applicable

Description of key information

IC50 (60 h): 119.62 mg/L (nominal)

Key value for chemical safety assessment

EC50 for microorganisms:
119.62 mg/L

Additional information

The toxicity of 2,5-Xylenol to aquatic microorganisms was investigated in a study on the ciliate Tetrahymena pyriformis. The ciliates were exposed to five different concentrations for a test period of 60 hours. Cell-population levels were estimated spectrophotometrically. The determined IC50 (60 h) was 119.62 mg/L (nominal) based on growth inhibition.