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Acute Toxicity: inhalation

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acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study was selected as the key study because the information provided for the hazard endpoint is sufficient for the purpose of classification and labelling and/or risk assessment.

Data source

Reference Type:
study report
Report Date:

Materials and methods

Test guidelineopen allclose all
according to
OECD Guideline 403 (Acute Inhalation Toxicity)
Conducted according to the guideline in effect at the time of study conduct.
according to
EPA OPPTS 870.1300 (Acute inhalation toxicity)
Conducted according to the guideline in effect at the time of study conduct.
GLP compliance:
Test type:
standard acute method
Limit test:

Test material

Details on test material:
- Purity: >99.9%

Test animals

other: Crl:CD(SD)
Details on test animals and environmental conditions:
- Age at study initiation: approximately 8 weeks
- Weight at study initiation: 276 - 294 g (males) and 207 - 226 g (females)
- Fasting period before study: No
- Housing: Individual suspended wire-mesh cages
- Diet (e.g. ad libitum): ad libitum, except during the exposure period
- Water (e.g. ad libitum): ad libitum, except during the exposure period
- Acclimation period: Minimum of 7 days

- Temperature (°C): targeted to 22±3°C (actual 21.3 - 21.5°C)
- Humidity (%): targeted to 50±20% (actual 35.9 - 48.1%)
- Air changes (per hr): Not reported
- Photoperiod (hrs dark / hrs light): 12 hrs dark/12 hrs light

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure:
nose only
other: oxygen and humidified air
Details on inhalation exposure:
- Exposure apparatus: 7.9-L conventional nose-only exposure system
- Exposure chamber volume: 7.9-L
- Method of holding animals in test chamber: nose-only exposure holding tubes
- Source and rate of air: source not reported; total airflow rate was 25.3 L/min
- Method of conditioning air: Not reported
- System of generating particulates/aerosols: The test substance was metered at a known flow rate by a liquid metering pump at the of a glass bead vaporisation column filled with 6-, 12-, and 16-mm glass beads. The bead column was wrapped with an Omega electric heating tape controlled using a J-type thermocouple and digital temperature controller set to maintain a temperature of 126-135°C. Using a Coilhose Pneumatics Regulator and a Linde rotameter-type flowmeter, compressed air was metered to the bottom of the vaporisation column. Vaporisation occurred as the liquid test substance coated the surfaced of the heated beads and air flowed up through the column. The test substance vapours were piped to a tee prior to the nose-only system where the concentration mixed with oxygen and humidified air. Oxygen was added from a compressed oxygen cylinder using a regulator and an Omega rotameter-type flowmeter. Humidified air was added using a Coilhose Pneumatics Regulator. A rotameter-type flowmeter was added to control the compressed air that passed through a muffler-type bubbler submerged in a 2-L Erlenmeyer flask filled with deionized water. The aerosol atmosphere was delivered to the nose-only exposure system through ¾-inch Tygon® tubing.
- Treatment of exhaust air: The exhaust atmosphere passed through the in-house exhaust system before being released from the facility.
- Temperature, humidity, pressure in air chamber: 25±1.3°C, 41±6.8, pressure not reported

- Brief description of analytical method used: The nominal exposure concentration was calculated for the exposure as the total amount of test substance used during the exposure divided by the total volume of air that passed through the chamber during the exposure, using the following equation:

Nominal Concentration (ppm) = (Test substance Used [g] x MW x 10E6) / (TAV x GMW) where:
MW = Molar volume at 730 mm Hg and 21°C, 25.11 L/mole
GMW = Gram molecular weight of the test substance, 164 g/mole
TAV = Total air volume of exposure, L
10E6 = ppm conversion

Analysed exposure concentrations were determined at approximately 60-minute intervals using a gas chromatograph (GC). Samples of the exposure were collected from the chamber using an internal gas-sampling valve and sample loop. The chromatograph was displayed and the area under the sample peak was calculated and stored. The concentration in parts per million (ppm) was calculated using a ln-quadratic formula based on the GC calibration curve. The GC was calibrated using gas-phase standards prepared to contain known vapour concentrations of the test substance prepared in 10-L Tedlar® gas bags. Standard bags were prepared by metering a known amount of air into the bag using a dry test meter and injecting a known volume of test substance. Using a hand-held heated blower, the bag was warmed until total volatilization of the test substance was visually observed. A sample was collected from the bag for approximately 8 minutes prior to being run through the GC. Prior to initiating animal exposure, the GC was calibrated with standards prepared and analysed in triplicate. The calibration curve was defined using standards prepared at 4 vapour concentrations spanning an appropriate range relative to the target exposure concentrations for the study. Thee prime calibration curve was prepared for the target concentration using the quadratic formula. On the day of exposure, 1 of the 4 standards was prepared and analysed, and the prime calibration curve was used to perform a calibration check of the GC.

- Samples taken from breathing zone: Not reported
Analytical verification of test atmosphere concentrations:
Mean measured concentration was 102900 ppm with a standard deviation of 5549 ppm
Duration of exposure:
4 h
102900 ppm
No. of animals per sex per dose:
Control animals:
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations: Each animal was observed for mortality at the approximated midpoint of the exposure, immediately following exposure on study day 0 and twice daily thereafter for 14 days. Each animal was observed for clinical signs immediately following exposure on study day 0 and once daily thereafter for 14 days.
- Frequency of weighing: Body weights were obtained immediately prior to exposure on study day 0 and on post-exposure days 7 and 14.
- Necropsy of survivors performed: yes
Not applicable

Results and discussion

Effect levels
Dose descriptor:
Effect level:
> 102 900 other: ppm (690413 mg/m3)
Based on:
test mat.
Exp. duration:
4 h
Remarks on result:
other: highest achievable vapour concentration
None of the animals died during exposure or during the 14-day observation period.
Clinical signs:
other: Immediately following exposure, tremors were observed for 2 males and 1 female, and rales were observed for 2 females. There were no other toxicologically significant clinical signs immediately following exposure. Several animals were noted with clear m
Body weight:
There were no remarkable changes in body weight. All animals surpassed their initial (study day 0) body weight by study day 14 and were considered normal.
Gross pathology:
The only macroscopic finding noted during the scheduled necropsy was clear fluid contents in the uterus for 1 female. This finding was considered spurious and not related to test material exposure. There were no other macroscopic findings for animals at the scheduled necropsy.

Applicant's summary and conclusion

Interpretation of results:
study cannot be used for classification
Migrated information
4-hour LC50 (rats) >102900 ppm (690413 mg/m3; highest achievable vapour concentration)

The study and the conclusions which are drawn from it fulfil the quality criteria (validity, reliability, repeatability).
Executive summary:

The acute inhalation toxicity of the test substance was conducted according to OECD Guideline 403 and OPPTS Guideline 870.1300. The test substance was evaluated in a 4-hour, single-exposure study in rats. The test substance was administered to one group of 5 male and 5 female CRl:CD(SD) albino rats via nose-only exposure as a vapour at a concentration of 102900 ppm, the highest achievable vapour concentration. Mortality, clinical observations, body weights and body weight changes were evaluated over a 14-day post-exposure observation period. Necropsies were conducted on all animals. 

None of the animals died during the exposure or the 14-day post-exposure observation period. Clinical observations immediately following exposure included tremors and rales. There were no toxicologically significant clinical signs during the 14-day post-exposure observation period, and all animals were considered clinically normal by study day 1. There were no remarkable changes in body weight. All animals surpassed their initial (study day 0) body weight by study day 14 and were considered normal. The only macroscopic finding noted during the scheduled necropsy was clear fluid contents in the uterus for 1 female. This macroscopic finding is considered spurious and not related to test material exposure. Based on the results of this study, the LC50 of the test substance was greater than 102900 ppm (690419 mg/m3), the highest achievable vapour concentration, when male and female albino rats were exposed to a vapour of the test substance as a single, 4-hour, nose-only exposure.