tert-butyl peroxyisobutyrate

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2013-04-11 to 2013-04-26

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2013

Report date:

2013

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Version / remarks:

07 September 2009

Deviations:

yes

Remarks:

only one animal group was treated in the Main Study.

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.2 (Acute Toxicity (Inhalation))

Version / remarks:

30 May 2008

Deviations:

yes

Remarks:

only one animal group was treated in the Main Study.

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.1300 (Acute inhalation toxicity)

Version / remarks:

August 1998

Deviations:

yes

Remarks:

only one animal group was treated in the Main Study.

GLP compliance:

yes (incl. QA statement)

Test type:

standard acute method

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

tert-butyl peroxyisobutyrate

EC Number:

203-650-5

EC Name:

tert-butyl peroxyisobutyrate

Cas Number:

109-13-7

Molecular formula:

C8H16O3

IUPAC Name:

tert-butyl 2-methylpropaneperoxoate

additive 1

Reference substance name:

2,2,4,6,6-pentamethylheptane

EC Number:

236-757-0

EC Name:

2,2,4,6,6-pentamethylheptane

Cas Number:

13475-82-6

Molecular formula:

C12H26

IUPAC Name:

isododecane

Test material form:

liquid

Specific details on test material used for the study:

Stabilizer: isododecane

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Toxi-Coop Zrt., Cserkesz u. 90., H-1103 Budapest, Hungary
- Age at study initiation: Young adult rats, 8 weeks old
- Weight at study initiation: Male: 267-282 g, Female: 204-217 g
- Housing: individually
- Diet: ssniff® SM R/M-Z+H complete diet for rats and mice produced by ssniff Spezialdiäten GmbH, ad libitum
- Water: tap water, ad libitum
- Acclimation period: 7 days
- Acclimatisation to the test apparatus: 3 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 30 – 70
- Air changes (per hr): 8-12
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 2013-06-11 To: 2013-06-26

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

nose only

Vehicle:

air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: anodised aluminium Flow Past Exposure Chamber (CR Equipment SA, Switzerland).
- Exposure chamber volume: 1.66 L
- Method of holding animals in test chamber: animals were held in polycarbonate restraining tubes and exposed “nose-only” under dynamic air flow conditions
- Source and rate of air: The air was supplied by an oil-free air compressor and was filtered in a two-stage filter set. The air was not humidified in order to avoid false results at gravimetry of the sampling tubes produced by adsorbed water vapour.
- Method of conditioning air: In the particular set-ups according to the pre-set total airflow rate the proper number of the radial tubes were plugged, and in such a way was ensured 1 L/min fresh test atmosphere to each animal port, sufficient to exclude re-breathing of the animals and to maintain natural oxygen concentration in the breathing zones.
- System of generating vapour atmosphere: The vapour of the test item was generated in a gas washing bottle (bubbler) with an airstream of 5 L/min. The bubbler was attached through a T junction to the input port on the top of the exposure chamber. In the first sighting exposure the other input branch of the junction was closed, while in the second sighting exposure and in the main study exposure the concentration of test atmosphere was set by additional clear air of 15 L/min and 8 L/min, respectively.

TEST ATMOSPHERE
- Brief description of analytical method used:
During these experiments it was found that due to different evaporation rates of the two components (TBPIB, active ingredient and Isododecane, stabilizer) the composition of the test item's vapour may be different from the composition of the liquid form. Therefore study concentration measurement via gravimetry was not sufficient and chemical analysis was also performed.
For sampling of the test atmosphere charcoal-filled sorbent tubes type Anasorb 747 (SKC Inc., Lots: 7006 and 7599) were implemented based on OSHA Sampling and Analytical Methods: Organic Vapors, 07, May 2000. At the time of the technical trials sampling procedure and method for chemical analysis were developed and validated. The mass of the test item's vapour adsorbed in the sampling tubes was measured both via gravimetry and chemical analysis. The analytical method implemented was reverse phase HPLC technique using UV absorption of TBPIB at 210 nm. In such a way the results did not depend on the amount of Isododecane in the samples. However, the method was calibrated directly with 75% TBPIB, therefore the mass of samples given by chemical analysis is test item equivalent mass (i.e. 74.3% TBPIB plus 25.7% Isododecane, according to the Test Item Characterization Sheet). Isododecane in excess does not appear in the result of chemical analysis, and was calculated as the difference of gravimetric mass of the sample and of the mass of TBPIB. This latter was determined as 74.3% of the test item's mass given by chemical analysis.
Investigation of sample stability at 6 and 24 hours revealed a reproducible temporal degradation (recovery rate: 75 and 65 %, respectively). Accordingly in the study the samples were analyzed after about 6 hours and the corresponding recovery correction factor (1/0.75) was implemented.
- Samples taken from breathing zone: yes

VEHICLE
- Composition of vehicle: air

TEST ATMOSPHERE
- Particle size distribution: Since no condensation of the test item from vapour to aerosol was detected by the light scattering aerosol photometer that is part of the exposure system, particle size analysis was neither planned nor performed in the study.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

ca. 4 h

Concentrations:

First sighting study: 6.8 mg/L 75% TBPIB
Second sighting study: 1.51 mg/L 75% TBPIB
Main Study: 2.53 mg/L 75% TBPIB

No. of animals per sex per dose:

First sighting study: 1/1
Second sighting study: 1/1
Main Study: 5/5

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days in the Main Study
- Observation for Morbidity / mortality: twice daily
- Frequency of observations: after one, two and three hour exposure whilst the animals are still restrained; as soon as practicable after removal from restraint on completion of the exposure; approximately one hour after completion of the exposure and then at least once daily for fourteen days.
- Frequency of weighing: Individual body weights were recorded with an accuracy of 1 g on the day of exposure Day 0 (prior to exposure) and Days 1, 3, 7 and 14.
- Necropsy of survivors performed: yes

Statistics:

not applicable

Results and discussion

Preliminary study:

One group of animals (1 male and 1 female) was exposed to test item atmosphere at the highest attainable concentration. The achieved total vapour concentration was 9.5 mg/L (gravimetry) with test item (i.e. 75% TBPIB) concentration of 6.81 mg/L (chemical analysis). Both animals died within 24 hours post-exposure.
A second sighting exposure at the total vapour concentration of 2.10 mg/L (gravimetry) was performed. Chemical analysis failed and the 75% TBPIB concentration was calculated from the total vapour concentration as 1.51 mg/L, based on the test item vs. total vapour ratio of 0.72 obtained in the first sighting exposure. 1 male and 1 female rat were tested, and no mortality appeared in 5 days postexposure.

Effect levels

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 2.53 - < 6.8 mg/L air (analytical)

Based on:

test mat.

Remarks:

75% TBPIB

Exp. duration:

4 h

Remarks on result:

other: One male animal died on day of exposure.

Mortality:

One animal died one day after completion of the exposure.

Clinical signs:

other: In the male and female animals test item related clinical signs were found between the fourth hour of inhalation exposure and on Day 1 of observation period. Clinical signs were decreased activity, bloody discharge around the nose, dyspnoea, tremor, vocal

Body weight:

In both genders body weight loss was observable on the day of inhalation exposure. In both sexes a compensation of body weight loss was found from Day 3 of observation period. On basis of body weight and body weight gain data, there was no notable test item effect observable in the exposed animals.

Gross pathology:

In the male dose group of 2.53 mg 75% TBPIB/L (5 animals): One animal died during the study. In this case the lungs were reddish mottled and the liver was dark coloured. In the surviving animals macroscopic alteration could not be found.
In the female dose group of 2.53 mg 75% TBPIB/L (5 animals): In one case hydrometra occurred.

In the male animal died on Day 1 of post-exposure period the reddish mottled lungs and dark coloured liver was considered as test item related effect.
The hydrometra is an alteration with sporadic occurrence in experimental rats without toxicological meaning.
In the surviving animals no macroscopic alterations in connection with the toxicological effect of the test item could be observed. 75% TBPIB did not cause local irritancy in the respiratory tract.

Other findings:

not applicable

Applicant's summary and conclusion

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

Under the experimental conditions of the present Acute Inhalation Toxicity Study, one of ten animals exposed to a mean achieved atmospheric test item vapour concentration of 2.53 mg/L for four hours died. Due to mortalitiy of both animals in the first sighting study at a test atmosphere concentration of 6.8 mg/L the acute inhalation median lethal concentration (4 hr LC50) of test item in Wistar Crl:(WI) BR rats was considered to be greater than 2.53 mg/L and below 6.8 mg/L. The test item was therefore shown to fulfill the criteria of Acute Toxicity Category 3 of the GHS/CLP system.

Executive summary:

The study was designed to assess the acute inhalation toxicity of test item. The results of the study are believed to be of value in predicting toxicity in humans by the inhalation route and the data obtained may serve as a basis for classification, labelling and hazard assessment according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS, United Nations 2011) and Regulation (EC) No 1272/2008 (CLP). The method used followed that described in the US Environmental Protection Agency (EPA) Health Effects Test Guidelines, OPPTS 870.1300, Acute Inhalation Toxicity, August 1998. The method was also designed to meet OECD guideline 403 (May 1981 and continuous series) and Commission Regulation (EC) No 440/2008, Annex Part B, B.2: "Acute Toxicity (Inhalation)", Official Journal of the European Union No. L 142, dated May 31st, 2008, in line with the Sponsor requirements.

A group of ten Wistar Crl:(WI) BR rats (five males and five females) was exposed to an atmosphere containing the vapour of the test item. The animals were exposed for four hours using a nose-only exposure system, followed by a fourteen day observation period. The concentration of the test item in the test atmosphere was determined by chemical analysis of samples gathered on charcoal sorbent tubes. Test item concentration for the Main study exposure was selected according to the result of two sighting exposures.

Following the first sighting exposure with the highest technically attainable test item concentration of 6.8 mg/L both treated animals died, while the second exposure at the concentration of 1.51 mg/L did not cause mortality. The Main study exposure was performed at the test item concentration elevated above the 2 mg/L border of GHS/CLP categories 2 and 3. The mean atmospheric concentration (achieved) and the nominal concentration of the test item was as follows:

 

Mean Achieved Concentration ± SD (mg/L air): 2.53±065 mg/L air

Nominal concentration: 4.87 mg/L air

 

Test item related clinical signs were found between the fourth hour of inhalation exposure and Day 1 of the observation period. Clinical signs were decreased activity, bloody discharge around the nose, dyspnoea, tremor, vocalisation, incoordination, crouching position and piloerection. One male animal died one day after completion of exposure. In this animal decreased activity, tremor, piloerection and dyspnoea were found in the fourth hour of inhalation exposure and one hour after completion of exposure. The surviving animals were symptom–free from Day 2 of observation period. In both genders body weight loss was observable on the day of inhalation exposure. In both sexes a compensation of body weight loss was found from Day 3 of the observation period. On basis of body weight and body weight gain data, there was no notable test item effect observable in the exposed animals. In the surviving animals macroscopic alteration in connection with the toxicological effect of the test item could not be observed. The test item did not cause local irritancy in the respiratory tract. In the male animal died on Day 1 of post-exposure period the reddish mottled lungs and dark coloured liver were considered as test item related effect.

Under the experimental conditions of the present Acute Inhalation Toxicity Study, one of ten animals exposed to a mean achieved atmospheric test item vapour concentration of 2.53 mg/L for four hours died. Due to mortalitiy of both animals in the first sighting study at a test atmosphere concentration of 6.8 mg/L the acute inhalation median lethal concentration (4 hr LC50) of test item in Wistar Crl:(WI) BR rats was determined to be greater than 2.53 mg/L and below 6.8 mg/L. The test item was therefore shown to fulfill the criteria of Acute Toxicity Category 3 of the GHS/CLP system.