tert-butyl perbenzoate

Endpoint summary

Description of key information

The test substance showed no sensitization in a Buehler study after induction at 75% in ethanol (minimally irritating( and challenge at 25% (highest non-irritating concentration). However, in a LLNA study, the substance resulted to extreme high SI scores in the LLNA at 25%, 50 and 100% in DMF of 20.0, 28.2, and 32.8 respectively.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Conducted according to OECD 402, in full comformance with GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

yes

Remarks:

The relative humidity in the animal room was between approximately 21 - 65 % for few hours, due to maintenance. This deviation to the study plan, however, does not affect the validity of the study.

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

other: CBA/CaOlaHsd

Sex:

female

Details on test animals and environmental conditions:

Test system Mice, CBA/CaOlaHsd
Rationale Recognised as the recommended test system
Source Harlan Laboratories B.V.
Postbus 6174
5960 AD Horst / The Netherlands
Number of animals for
the pre-test 2 females
Number of animals for
the main study
20 females
Number of animals per group 5 females (nulliparous and non-pregnant)
Number of test groups 3
Number of control (vehicle) groups 1
Age 8 - 12 weeks (beginning of treatment)
Body weight 18.9-23 g
Identification Single caging. The animals were distributed into the test groups at random and identified by cage number.
Acclimatisation At least 5 days prior to the start of dosing under test conditions after health examination. Only animals without any visible signs of illness were used for the study.

The animals were kept conventionally. The experiment was conducted under standard laboratory conditions.
Housing: single
Cage Type: Makrolon Type II, with wire mesh top
(EHRET GmbH, 79302 Emmendingen, Germany)
Bedding: granulated soft wood bedding
(Rettenmaier & Söhne GmbH + Co. KG, 73494 Rosenberg, Germany)
Feed: pelleted standard diet, ad libitum
(Harlan Laboratories B.V., 5960 AD Horst / Netherlands)
Water: tap water, ad libitum,
(Gemeindewerke, 64380 Rossdorf, Germany)
Environment: temperature 22 + 2°C
relative humidity 21-65%
artificial light 6.00 a.m. - 6.00 p.m.

Vehicle:

dimethylformamide

Concentration:

0, 25%, 50%, & 100%

No. of animals per dose:

5

Details on study design:

4.3 Experimental Design and Procedures
4.3.1 Topical Application
Each test group of mice was treated by topical (epidermal) application to the dorsal surface of each ear lobe (left and right) with different test item concentrations of 25, 50, and 100% (w/v) in dimethylformamide. The application volume, 25 µl, was spread over the entire dorsal surface (  8 mm) of each ear lobe once daily for three consecutive days. A further group of mice was treated with an equivalent volume of the relevant vehicle alone (control animals).
4.3.2 Administration of 3H-Methyl Thymidine
3H-methyl thymidine (3HTdR) was purchased from GE Healthcare (GE Healthcare product code no. TRA 310; specific activity, 2 Ci/mmol; concentration, 1 mCi/ml).
Five days after the first topical application, all mice were administered with 250 µl of 80.7 µCi/ml 3HTdR (corresponds to 20.2 µCi 3HTdR per mouse) by intravenous injection via a tail vein.
4.3.3 Determination of Incorporated 3HTdR
Approximately five hours after treatment with 3HTdR all mice were euthanised by intraperitoneal injection of Pentobarbital-Natrium (Release, WDT, D-30827 Garbsen).
The draining lymph nodes were rapidly excised and pooled per group (8 nodes per group). Single cell suspensions (in phosphate buffered saline) of pooled lymph node cells were prepared by gentle mechanical disaggregation through stainless steel gauze (200 µm mesh size). After washing two times with phosphate buffered saline (approx. 10 ml) the lymph node cells were resuspended in 5 % trichloroacetic acid (approx. 3 ml) and incubated at approximately +4 °C for at least 18 hours for precipitation of macromolecules. The precipitates were then resuspended in 5 % trichloroacetic acid (1 ml) and transferred to plastic scintillation vials with 10 ml of ‘Ultima Gold’ scintillation liquid (Perkin Elmer (LAS) GmbH, D-63110 Rodgau) and thoroughly mixed.
The level of 3HTdR incorporation was then measured on a -scintillation counter (Tricarb 2900 TR, Perkin Elmer (LAS) GmbH, D-63110 Rodgau). Similarly, background 3HTdR levels were also measured in two 1ml-aliquots of 5 % trichloroacetic acid. The -scintillation counter expresses 3HTdR incorporation as the number of radioactive disintegrations per minute (DPM).

Key result

Parameter:

SI

Value:

20.04

Test group / Remarks:

In this study Stimulation Indices (S.I.) of 20.04, 28.16, and 32.77 were determined with the test item at concentrations of 25, 50, and 100% in dimethylformamide, respectively.

Key result

Parameter:

SI

Value:

28.16

Test group / Remarks:

In this study Stimulation Indices (S.I.) of 20.04, 28.16, and 32.77 were determined with the test item at concentrations of 25, 50, and 100% in dimethylformamide, respectively.

Key result

Parameter:

SI

Value:

32.77

Test group / Remarks:

In this study Stimulation Indices (S.I.) of 20.04, 28.16, and 32.77 were determined with the test item at concentrations of 25, 50, and 100% in dimethylformamide, respectively.

Interpretation of results:

sensitising

Conclusions:

The test item tert-Butyl peroxybenzoate was found to be a skin sensitiser under the described conditions.

Executive summary:

In the study the test item tert-Butyl peroxybenzoate dissolved in dimethylformamide was assessed for its possible contact allergenic potential.

For this purpose a local lymph node assay was performed using test item concentrations of 25, 50, and 100%.

The animals did not show any signs of systemic toxicity during the course of the study and cases of mortality were not observed. 24 after the first and second application and 1 hour after the second and third application all animal of the mid dose (50%) showed slight redness of the ear skin and all animals of the high dose (100%) showed swollen ears. All animals of the high dose (100%) also showed slight redness of the ear skin 24 hours after the second and 1 hour after the third application. However, these local signs of irritation resolved until the day of preparation (day 6). Animals treated with a concentration of 25% did not show any local signs of irritation during the course of the study.

In this study Stimulation Indices (S.I.) of 20.04, 28.16, and 32.77 were determined with the test item at concentrations of 25, 50, and 100% in dimethylformamide, respectively.

The test item tert-Butyl peroxybenzoate was found to be a skin sensitiser.

Reference 2

Endpoint:

skin sensitisation: in vitro

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

t-Butyl Peroxybenzoate, was evaluated for skin sensitization in Guinea pigs by the modified technique of Buehler.
30 guinea pigs were used (15 male; 15 female): 6 for preliminary irritation study to select concentrations, 4 for positive control DNCB, 10 for test (induction & challenge) & 10 for control (challenge only). In the preliminary study animals were treated with 0.5 mL of test substance in ethanol at concentrations of 25, 50, 75 and 100% for 6 hrs. Scoring after 24 hrs showed 75% to produce slight irritation, selected for use for induction, and 25% to be the highest non-irritating concentration, selected for challenge.
Induction: 75% once per week, for three weeks; Challenge: 25% two weeks after last induction. A rechallenge was performed 1 week later due to equivocal responses.
Results: After challenge, erythema (Grade 1) was observed in five t-Butyl Peroxybenzoate-induced guinea pigs at 24 hours and in four guinea pigs at 48 hours. Erythema (Grade 1) was noted in one non induced guinea pig at 24 and 48 hours. No edema was seen in the induced or non-induced guinea pigs at 24 or 48 hours. On the basis of the equivocal response of slight irritation in the induced guinea pigs, a rechallenge was conducted.
Upon rechallenge, erythema (Grade 1) was observed in one t-Butyl Peroxybenzoate-induced guinea pig at 24 hours and in two guinea pigs at 48 hours. In the non-induced guinea pigs scored even more: erythema (Grade 1) was noted at 24 hours in two guinea pigs and at 48 hours in four guinea pigs. No edema was observed in the induced or non-induced guinea pigs at 24 or 48 hours. Overall it can be considered that there are no differences in reaction observed between induced and non-induced animals. The results of this study suggest that t-Butyl Peroxybenzoate does not have the potential to be a dermal sensitizer in guinea pigs.

tert-Butyl peroxybenzoate was further assessed for contact allergenic potential in a local lymph node assay (LLNA, OECD 429) in mice, using concentrations of 25, 50, and 100% dissolved in dimethylformamide.
The animals did not show any signs of systemic toxicity during the course of the study and cases of mortality were not observed. 24 hours after the first and second application and 1 hour after the second and third application all animals of the mid dose (50%) showed slight redness of the ear skin and all animals of the high dose (100%) showed swollen ears. All animals of the high dose (100%) also showed slight redness of the ear skin 24 hours after the second and 1 hour after the third application. However, these local signs of irritation resolved until the day of preparation (day 6). Animals treated with a concentration of 25% did not show any local signs of irritation during the course of the study.
In this study Stimulation Indices (S.I.) of 20.04, 28.16, and 32.77 were determined with the test item at concentrations of 25, 50, and 100% in dimethylformamide, respectively.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Test substance provided clearly positive results in the LLNA.