2,6-di-tert-butyl-p-cresol

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

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.