Divanadium trioxide

Specific investigations: other studies

Administrative data

Endpoint:

mechanistic studies

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2010-03-11 to 2010-07-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2011

Report date:

2011

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: OECD 436 "Acute Inhalation Toxicity - Acute Toxic Class Method" (adopted 2009-09-07)

Deviations:

yes

Principles of method if other than guideline:

The limit test for this study (2.0 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:

yes

Type of method:

in vivo

Endpoint addressed:

acute toxicity: inhalation

Test material

Test material information

Constituent 1

Reference substance name:

Divanadium trioxide

EC Number:

215-230-9

EC Name:

Divanadium trioxide

Cas Number:

1314-34-7

Molecular formula:

O3V2

IUPAC Name:

Divanadium trioxide

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

- Name of test material (as cited in study report): granular vanadium trioxide
- Physical state: black powder
- Storage condition of test material: at room temperature

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories (Portage, MI)
- Age at receipt: males: 55 days; females: 59 days
- Weight at receipt: 133 to 172 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 Diet No. 5002 meal (PMI Nutrition International, Inc., Brentwood, MO)
- Water (ad libitum, except during inhalation exposure): City of Chicago water
- Quarantine period: at least one week
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.

ENVIRONMENTAL CONDITIONS
- Temperature: 18 to 24°C
- Relative humidity: 30 to 68%
- Air changes: minimum of 10 air changes per hour
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

inhalation: aerosol

Vehicle:

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.

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- 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 22 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 were recorded at approximately half-hour intervals during exposure.
Temperature (mean ± SD):
2.03 mg/L: 21.2°C ± 0.27
1.05 mg/L: 22.0°C ± 0.49
Relative humidity (mean ± SD):
2.03 mg/L: 15.3% ± 3.28%
1.05 mg/L: 18.5% ± 4.38%
Oxygen (%):
2.03 mg/L: 20.8%
1.05 mg/L: 20.8%

- Method of particle size determination: aerosol particle size distribution was monitored at least once per two hours during the exposure with a quartz crystal microbalance (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.

TEST ATMOSPHERE
- 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 chemically by ICP-MS for determination of vanadium content and to confirm the gravimetric weight measurement.
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

TEST ATMOSPHERE
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.):
2.03 mg/L: 2.49 µm (GSD: 1.50 to 1.90)
1.05 mg/L: 2.53 µm (GSD: 1.96 to 2.04)

Analytical verification of doses or concentrations:

yes

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:

once

Post exposure period:

14 days

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
1.05 and 2.03 mg/L
Basis:
analytical conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
1.0 and 2.0 mg/L
Basis:
nominal conc.

No. of animals per sex per dose:

2.03 mg/L: 5 males / 5 females
1.05 mg/L: 6 females

Control animals:

no

Details on study design:

A group of five male and five female rats was exposed to an aerosol of granular vanadium trioxide 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 (two out of five females), an additional group of six female rats was exposed at a concentration of 1.0 mg/L. Surviving animals were observed for a 14-day post-exposure period.

Examinations

Examinations:

- 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 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 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 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 to be retained for possible pathologic evaluation, when considered needed.

Positive control:

not applicable

Results and discussion

Details on results:

LC50 (4 hours, male rats) > 2 mg/L
1.0 mg/L < LC50 (4 hours, female rats) < 2.0 mg/L
- Mortality and clinical observations: the 2.0 mg/L exposure concentration resulted in compound-related mortality of two out of five female animals, while no male animals at the 2.0 mg/L level died prior to scheduled sacrifice. The 1.0 mg/L exposure concentration resulted in compound-related mortality of one out of the six female animals.
Skin/fur discolouration (black) was seen in all animals, and wet inguinal fur was seen in most animals of all groups, during the exposure periods. Clinical signs of toxicity were not observed for males in the 2.0 mg/L group. For the females in the 2.0 mg/L exposure group, dehydration, redness around the eyes and rough coat were observed on one or more occasions. For the females in the 1.0 mg/L exposure group, hypoactivity, hunched posture, discoloured (brown) inguinal skin/fur and black material around the nose were also observed on one or more occasions. these clinical signs were either an indication of toxicity (hypoactivity; rough coat; hunched posture; dehydration) or were considered to have resulted from exposure to the test article in the nose-only exposure tubes (black skin/fur discolouration, black material around the nose, redness around the eyes) or from being restrained in the nose-only exposure tubes (wet/discoloured inguinal skin/fur).
- Body weights and body weight gains: all male rats (2.0 mg/L) gained weight during the study, with the majority of the gain during the second week of recovery. Surviving females in the 2.0 mg/L group lost weight during the first week of recovery and gained weight during the second week of recovery. Surviving females in the 1.0 mg/L group either lost weight or maintained weight during the first week of recovery and gained weight during the second week of recovery.
- Necropsy: at necropsy for the 2.0 mg/L exposure group, mottled or pale pink lungs were observed in five of the five males (all terminal sacrifices), along with a dark red focus/foci in four of these animals. Mottled and/or pale pink lungs were observed in the three surviving females in the 2.0 mg/L group, along with a dark red focus/foci. The lungs of the two female animals in the 2.0 mg/L group were found dead on Days 5 and 10 were described as mottled and bright red respectively. For the 1.0 mg/L group, mottled and dark red/pale pink lungs were observed in all of the six females in that exposure group; white foci were also observed in one of these animals.

Applicant's summary and conclusion

Conclusions:

The acute inhalation toxicity of granular vanadium trioxide was tested in rats as an aerosol and resulted in the following:
LC50 (4 hours, male rats) > 2 mg/L
1.0 mg/L < LC50 (4 hours, female rats) < 2.0 mg/L