Registration Dossier

Ecotoxicological information

Toxicity to microorganisms

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study meets generally accepted scientific principles but the publication reports several chemicals, therefore exhaustive details are not provided.
Principles of method if other than guideline:
The method was carried out under sterile conditions. Tetrahymena pyriformis was pre-cultured at 30 ºC for 24 h. The stock solution of the chemical was added to the sterile medium to provide a concentration ratio of 1.8 in 10 ml of 2% proteose peptone. The solutions were then inoculated with 0.2 mL of pre-cultured T. pyriformis and cultivated at 30 ºC for 24 h without agitation. The number of cells was then counted.
GLP compliance:
not specified
Analytical monitoring:
not specified
Vehicle:
yes
Details on test solutions:
Several chemicals were tested: a stock solution of each test chemical at high concentration was prepared and stored in a refrigerator. Water-soluble chemicals were dissolved directly in water; those only slightly soluble in water were dissolved in dimethylsulfoxide (DMSO). DMSO did not affect the growth of T. pyriformis at 10000 mg/L and the test was carried out at a concentration of < 5000 mg/L. Since BHT is slightly soluble in water it can be assumed that DMSO was used as vehicle.
Test organisms (species):
Tetrahymena pyriformis
Details on inoculum:
Tetrahymena pyriformis was preserved in a sterile medium of 2% proteose peptone at 20 ºC which was renewed at 2-4 week intervals.
Test type:
static
Water media type:
freshwater
Total exposure duration:
24 h
Reference substance (positive control):
not specified
Key result
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
1.7 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth inhibition
Validity criteria fulfilled:
not specified
Conclusions:
The 24 -h EC50 for the substance dibutylhydroxytoluene (BHT) in Tetrahymena pyriformis was 1.7 mg/L.
Executive summary:

A study to assess the toxicity of BHT to the aquatic protozoa Tetrahymena pyriformis was conducted. The experimental animals were pre-cultured at 30 ºC for 24 h. The stock solution of the chemical was added to the sterile medium to provide a concentration ratio of 1.8 in 10 mL of 2% proteose peptone. The solutions were then inoculated with 0.2 ml of pre-cultured T. pyriformis and cultivated at 30 ºC for 24 h without agitation. The number of cells was then counted. The relative growth rate was calculated as the ratio of the number of cells cultured wth a chemical against the number cultivated in a blank. The effective concentration 50% (EC50) values were obtained by plotting the relative growth rates against the concentration of chemical on logarithmic-probability paper. The 24 -hour EC50 for BHT was 1.7 mg/L.

Description of key information

Tetrahymena pyriformis. EC50 (24h)= 1.7 mg/L based on growth inhibition.

The 30min-EC50 of BHT to Photobacterium phosphoreum based on light emission is 8.98 mg/L.

The 36h-NOEC of BHT to Pseudomona fluorescens based on the number of viable cells was 50 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
1.7 mg/L

Additional information

Weight of evidence

Tetrahymena pyriformis. EC50 (24h)= 1.7 mg/L based on growth inhibition.

The 30min-EC50 of BHT to Photobacterium phosphoreum based on light emission is 8.98 mg/L.

The 36h-NOEC of BHT to Pseudomona fluorescens based on the number of viable cells was 50 mg/L.