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mechanistic studies
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2010-04-14 to 2010-07-12
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
other: OECD 436 "Acute Inhalation Toxicity - Acute Toxic Class Method" (adopted 2009-09-07)
Principles of method if other than guideline:
The limit test for this study (2 mg/L) was conducted in compliance with the requirements of the following test guidelines with the exception that body weights were not obtained 1 and 3 days after exposure: 1) US EPA Health Effects Testing Guideline, OPTTS 870.1300, entitled Acute Inhalation Toxicity, 1998 and 2) OECD test guideline 403 (1981). In order to reduce animal use and to provide an acute inhalation toxicity estimate and information for the Globally Harmonized System (GHS) of classification and labelling for the test substance, all subsequent exposures were conducted in compliance with OECD test guideline 436 (2009) (with the exception that body weights were not obtained 1 and 3 days after exposure). The initial subsequent exposure was determined by the study director in conjunction with the sponsor and any subsequent exposures were determined according to the scheme in Annex 3c of the OECD 436 test guideline.
GLP compliance:
Type of method:
in vivo
Endpoint addressed:
acute toxicity: inhalation

Test material

Constituent 1
Chemical structure
Reference substance name:
Vanadium dioxide
EC Number:
EC Name:
Vanadium dioxide
Cas Number:
Molecular formula:
vanadium dioxide
Test material form:
solid: particulate/powder
migrated information: powder
Details on test material:
- Name of test material (as cited in study report): vanadium tetroxide (Treibacher Industrie AG, Althofen. Austria)
- Physical state: a greyish granular powder
- Storage condition of test material: at room temperature

Test animals

Fischer 344
Details on test animals or test system and environmental conditions:
- Source: Charles River Laboratories (Portage, MI)
- Age at receipt: 55 and 59 days
- Weight at receipt: 127 to 194 g
- Housing: animals of the same sex were double-housed and then after randomization, single-housed, in stainless steel cages suspended over absorbent paper cage boards
- Diet (ad libitum, except during inhalation exposure): Certified Rodent Chow 5002 meal (PMI Nutrition International, Inc., Brentwood, MO)
- Water (ad libitum, except during inhalation exposure): City of Chicago water
- Quarantine period: 8 and 13 days (2.0 and 1.0 mg/L exposure groups, respectively)
During quarantine the rats were observed daily for signs of disease and general unthriftiness.
To condition the animals to placement and restraint in the nose-only holding tubes (CH Technologies, U.S.A., Westwood, NJ) and to reduce stress during the exposure phase, the animals were placed in the holding tubes over three days according to the following schedule: one hour on Day 1, two hours on Day 2 and three hours on Day 3 prior to their exposure.

- Temperature: 18 to 22°C
- Relative humidity: 30 to 72%
- Air changes: minimum of 10 air changes per hour
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
inhalation: aerosol
clean air
Details on exposure:
An aliquot of the test substance was milled. The milled test substance was aerosolised as a powder for the inhalation exposures.

- Exposure apparatus/Method of holding animals in test chamber: a 52-port, flow-past nose-only inhalation exposure chamber (Lab Products Inc., Seaford, DE) was used. The animals were restrained in nose-only exposure animal holding tubes (CH Technologies, U.S.A., Westwood, NJ). Each tube was placed in a pre-designated port of the inhalation exposure chamber.

- System of generating particulates/aerosols: the test atmosphere was created by generating an aerosol (with filtered air) of the test substance using a compressed air-operated Wright Dust Aerosol Generation System (BGI Incorporated, Waltham, MA) positioned over the chamber. The test substance was weighed and packed into a dust reservoir forming a cake. A constant speed rotating scraper separated a thin film of the test substance at the surface of the cake and delivered it into a dispersing unit, drawn in by aspiration and dispersed by a high velocity air jet. The resulting test atmosphere entered a mixing plenum where it, when necessary, was diluted with breathable quality compressed air to achieve target concentration prior to introduction to the exposure chamber. The exhaust from the exposure chamber was moved through a high efficiency particulate air (HEPA) filter by a ring compressor and exhausted outside the building. Inlet and exhaust flows to and from the chamber were controlled and continuously monitored by rotometers.

T90 time was assessed to be less than 10 seconds.

- Temperature, humidity, oxygen percentage in air chamber: oxygen percentage was measured once during the exposure with an Altair Oxygen Sensor and Detector (MSA Instrument Division, Pittsburgh, PA).
Inhalation exposure chamber temperature and relative humidity were monitored with a hand-held thermohygrometer (model # 8721, Control Company, Fisher Scientific, Friendswood, TX) and recorded at approximately half-hour intervals during exposure.
Temperature (mean ± SD):
1.99 mg/L: 20.7°C ± 0.36
1.03 mg/L: 19.9°C ± 0.29
Relative humidity (mean ± SD):
1.99 mg/L: 25.2% ± 2.57%
1.03 mg/L: 19.7% ± 0.64%
Oxygen (%):
1.99 mg/L: 21.3%
1.03 mg/L: 20.8%

- Method of particle size determination: aerosol particle size was monitored at least once per two hours during the exposure with a QCM Cascade Impactor (California Measurements Inc., Sierra Madre, CA). The mass median aerosol diameter (MMAD) and geometric standard deviation (GSD) were calculated from the mass accumulated on each stage of the QCM.

- Brief description of analytical method used: the concentration of the test substance in the test atmosphere was monitored gravimetrically by filter-collected samples. One sample was taken from the breathing zone of the animals every hour of exposure. The gravimetric sampling train consisted of a pre-weighed filter in a series with a dry-gas meter connected to a constant flow vacuum pump. The dry-gas meter measured the corresponding volume of chamber air sampled and the weight to volume ratio was determined to obtain the aerosol mass concentration. Filter-collected samples were weighed, and one randomly-selected filter was analysed by ICP-MS.
Aerosol concentration was monitored with a real-time aerosol sensor (model #pDR-1000AN, MIE, Inc. Bedford, MA). The sensors were employed as a real-time indicator of short term changes in aerosol concentration.
- Samples taken from breathing zone: yes

- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.):
1.99mg/L: 2.46 µm (GSD: 2.21 to 2.34)
1.03 mg/L: 2.77 µm (GSD: 2.06 to 2.43)
Analytical verification of doses or concentrations:
Details on analytical verification of doses or concentrations:
Please refer to the field "Details on exposure" above.
Duration of treatment / exposure:
4 hours
Frequency of treatment:
Post exposure period:
14 days
Doses / concentrationsopen allclose all
Doses / Concentrations:
1.03 and 1.99 mg/L
analytical conc.
Doses / Concentrations:
1.0 and 2. 0 mg/L
nominal conc.
No. of animals per sex per dose:
1.99 mg/L: 5 males / 5 females
1.03 mg/L: 3 males / 3 females
Control animals:
Details on study design:
A group of five male and five female rats was exposed to an aerosol of vanadium tetroxide in a nose-only inhalation exposure chamber for 4 hours at a concentration of 2.0 mg/L. Due to the mortality observed at the 2.0 mg/L exposure concentration (four out of five males and five out of five females), an additional group of three male and three female rats was exposed under the same conditions at a concentration of 1.0 mg/L. Surviving animals were observed for a 14-day post exposure period.


- Mortality and clinical observation: the animals were observed for signs of toxicity during the exposure, immediately after the exposure and at least once daily during the 14-day post-exposure observation period. Cage side observations included, but were not limited to, changes in skin, fur, eyes and mucous membranes, respiratory and circulatory effects, autonomic effects such as salivation, effects on the central nervous system, and somatomotor activity and behaviour pattern. Particular attention was devoted to observation of tremors, convulsions, salivation, diarrhoea, lethargy, sleep, and coma.
- Body weights and body weight gains: body weights were determined one day after animal receipt, prior to randomization, on Day 1 prior to exposure, and one week after exposure. All surviving animals were weighed on the day of their scheduled necropsy, prior to euthanasia. Body weights of animals found dead were also collected prior to necropsy. Body weight changes were calculated for rats surviving more than 24 hours.
- Necropsy: all exposed animals, including those found dead, were subjected to gross necropsy. At the end of the observation period, all surviving animals were euthanized by an overdose of sodium pentobarbital (intraperitoneal injection) and subjected to a gross necropsy. The necropsy included examination of all body surfaces and openings, the external appearance of the brain, heart, liver, kidneys, lungs (especially any changes in the immediately associated and exposed respiratory tract), gastrointestinal tract, spleen, gonads and the urinary bladder. The gastrointestinal tract and the urinary bladder were opened and examined if lesions were present. Respiratory tracts were saved and fixed in 10% neutral buffered formalin. Abnormal tissue were also retained for possible pathologic evaluation, when considered needed.
Positive control:
not applicable

Results and discussion

Details on results:
1.0 mg/L < LC50 (4 hours, male and female rats) < 2.0 mg/L
LC50 (4 hours, male and female rats) = 0.25 mg/L
- Mortality and clinical observations: the 2.0 mg/L exposure concentration resulted in compound-related mortality of four out of five male animals and five out of five female animals. None of the three animals per sex in the 1.0 mg/L group died prior to scheduled sacrifice.
Skin/fur discolouration (black), discoloured/wet inguinal fur and hypoactivity were observed for most animals following exposure. Black material around the nose and/or discolouration around the mouth were observed in several instances, and one or more occurrences of irritability, rough coat and hunched posture were noted. These clinical signs were either an indication of toxicity (hypoactivity, rough coat and hunched posture) or were considered to have resulted from exposure to the test article in nose-only exposure tubes 8black skin/fur discolouration, black material around the nose, discolouration around the mouth) or from being restrained in the nose-only exposure tubes (wet inguinal fur).
- Body weights and body weight gains: for the 2.0 mg/l exposure, both the males and females lost weight from Days 1-8. For the 1.0 mg/L exposure, two males and all females lost weight during Week 2.
- Necropsy: for the 2.0 mg/L rats, the following gross lesions were observed at necropsy: lungs, mottled dark red (3 males and 2 females); lungs, pale pink 2 males and 1 female); liver, white lesion (1 female); lungs, dark red (1 female); and lungs, mottled (1 female). For the 1.0 mg/L rats, the following gross lesions were observed at necropsy: lungs, pale pink (2 males); lungs, pale pink mottled (1 male and 3 females); and a 2 mm white focus on the lung (1 female).

Applicant's summary and conclusion

The acute inhalation toxicity of vanadium tetroxide was tested in rats as an aerosol and resulted in the following: 1.0 mg/L < LC50 (4 hours, male and female rats) < 2.0 mg/L