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Administrative data

acute toxicity: inhalation
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
2002-08-21 to 2002-11-28
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Well documented, scientifically sound study that was conducted in accordance with GLP and OECD Guideline 403, "Acute Inhalation Toxicity." The reliability of this study for this substance tested is a K1, but in application of read-across to a different substance, ECHA's guidance specifies that the score can be a maximum of a K2.
Justification for type of information:
Tungstic acid (WO3•H2O) is the hydrated form of tungsten trioxide (WO3). Based on Annex V, hydrates and water free forms (anhydrous) of compounds can be regarded as the same substance for registration purposes. Therefore, tungstic acid will be considered equivalent to WO3. For more details on the rationale, refer to the attached description of the read-across approach (Annex 3).

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guidelineopen allclose all
according to guideline
OECD Guideline 403 (Acute Inhalation Toxicity)
according to guideline
EU Method B.2 (Acute Toxicity (Inhalation))
GLP compliance:
Test type:
acute toxic class method
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
Tungsten trioxide
EC Number:
EC Name:
Tungsten trioxide
Cas Number:
Molecular formula:
Details on test material:
- Name of test material (as cited in study report): Tungsten Oxide (WO3)
- Supplier: Sponsor
- Physical state: Yellow to greenish powder
- Analytical purity: 99.88%
- Purity test date: 2002-05-28
- Stability under test conditions: 5 years
- Storage condition of test material: Room temperature
- pH: 6.1 (aqu. suspension, 100 g/L)
- Solubility in water: < 10 mg/L WO3
- Melting point: Ca. 1473 degrees C

Test animals

other: Crl:CD(SD)IGS BR, Sprague Dawley, SPF
Details on test animals or test system and environmental conditions:
- Source: Charles River WIGA, Germany
- Age at study initiation: Approximately 9 weeks at time of administration
- Weight at study initiation: 305-336g (males), 207-225g (females)
- Housing: Housed singly in Makrolon cages type III (39 cm x 23 cm x 18 cm)
- Diet: Altromin 1324 forte, gamma irradiated with 25 kGy 60Co - ad libitum (withheld during the exposure)
- Water: Tap water from an automated watering system - ad libitum (withheld during the exposure)
- Acclimation period: At least 5 days

- Temperature (°C): Target of 22 ⁰C
- Humidity (%): Target of 50%
- Air changes (per hr): 12/hour
- Photoperiod (hrs dark / hrs light): 12 dark/12 light (6 am to 6 pm)

IN-LIFE DATES: From: 2002-08-21 To: 2002-09-25

Administration / exposure

Route of administration:
inhalation: dust
Type of inhalation exposure:
nose only
other: unchanged (no vehicle)
Details on inhalation exposure:
- Exposure apparatus: TSE, Technical & Scientific Equipment- article no. 504101. It consisted of a two chamber system. The apparatus was 30 cm in diameter and 27 cm in height, resulting in a total volume of 19 litres.
- Exposure chamber volume: 19 L
- Method of holding animals in test chamber: Trapped in outer chamber with opening to exposure chamber
- Source and rate of air: Obtained from a central pressure pump, 1836 L air/dust per hour
- System of generating particulates/aerosols: RBG 1000 dust generator
- Method of particle size determination: Cascade impactor (Berner-Impaktor Type LP14/0,06/2)
- Temperature, humidity, pressure in air chamber: 21-23 ⁰C, 12.7 to 16.0 %, approx. 3 bar.

- Brief description of analytical method used: gravimetric analysis- dust was collected 9 times during the exposure period in plastic pipette-tips filled with cotton wool, which were inserted into the inhalation facility through a separate hole between two inhalation tubes.
- Samples taken from breathing zone: yes

TEST ATMOSPHERE (if not tabulated)
- Particle size distribution: 64% of the mass was in the fraction with a diameter of less than 5 micrometers, the size distribution did not exactly follow a log-normal distribution but had an additional fraction of particles larger that 16 micrometers.
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): MMAD=3.7 micrometers, GSD= 2.3

Analytical verification of test atmosphere concentrations:
4.47- 5.87 mg/L (detected 9 times)
Duration of exposure:
ca. 4 h
- Mean concentration= 5.36 mg/L
No. of animals per sex per dose:
5 males and 5 females
Control animals:
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: observations- 1, 2, 3, 4, 5, and 6 hours after the start of the exposure, and then at least once a day for a total of 2 weeks.
- Body weight:
Individual- before administration, day 7, day 14, and post mortem
Body weight gain was calculated for each week of the study, 0 and 7 days post administration, 7 and 14 days post administration.
- Necropsy of survivors performed: Yes; in attempt to identify the target organs
no data

Results and discussion

Effect levels
Key result
Dose descriptor:
Effect level:
> 5.36 mg/L air
Exp. duration:
4 h
- All animals survived until the end of the study.
Clinical signs:
other: - Immediately after exposure the fur at the head of all animals was stained yellow (due to sedimentation of the test substance). - Three animals showed chromodacryorrhoea for a short time after the exposure. This is a sign of general malaise and may be c
Body weight:
- The mean body weights at the end of the exposure were 319 g for males and 216 g for females. The mean body weight gain in the first week after the exposure was 47 g for males and 16 g for females. In the second week males gained 43 g, females 14 g.
- No animal lost weight during the study.
Gross pathology:
- Nothing abnormal was seen in any of the animals.
Other findings:
- Other observations: No sex differences can be established from the results of this study.

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
The inhalation exposure of rats to Tungsten Oxide (WO3) at a concentration of 5.36 mg/L only produced signs of general malaise a short time after the exposure. The animals recovered within one hour and no further adverse effects were observed. The LC50, for four hours of exposure, Tungsten Oxide (WO3) for male and female rats was found to be greater than 5.36 mg/L air.
Executive summary:

No acute imhalation toxicity data are available for tungstic acid (target substance). However, acute inhalation toxicity data are available for tungsten trioxide (source substance), which were used for read-across. Tungstic acid (WO3•H2O) is the hydrated form of tungsten trioxide (WO3). Based on Annex V, hydrates and water free forms (anhydrous) of compounds can be regarded as the same substance for registration purposes. Therefore, tungstic acid will be considered equivalent to WO3. For more details on the rationale, refer to the attached description of the read-across approach.