Dipotassium tetraoxomolybdate

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1990-09-05 to 1990- 09-26

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Version / remarks:

adopted 12 May 1981

Deviations:

yes

Remarks:

minor temperature deviation (1°C); nominal concentration and 95 per centconficence level is missing.

GLP compliance:

yes

Remarks:

The study report states that the study was conducted in compliance with Good Laboratory Practice Standards, e.g. by the United Kingdom Compliance Programme, Department of Health & Social Security 1986 and subsequent revision, Department of Health, 1989.

Test type:

standard acute method

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Diammonium dimolybdate

EC Number:

248-517-2

EC Name:

Diammonium dimolybdate

Cas Number:

27546-07-2

IUPAC Name:

Diammonium dimolybdate

Details on test material:

- Name of test material (as cited in study report): Ammonium dimolybdate
- Physical state: white powder
- Analytical purity: ca. 99.9 %, calculted from reported Mo content (56.4%)
- Impurities (identity and concentrations): not stated
- Composition of test material, percentage of components: Mo =56.4%; NH4 = 10.5 %
- Stability under test conditions: Under test conditions the test substance was stable.
- Storage condition of test material: stored in the dark at room temperature and in the original container

No further significant information on test material was stated.

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS (albino rats)
- Age at study initiation: about 6 weeks (males) and 8 weeks (females) old
- Weight at study initiation: ca. 200g on the day of exposure
- Housing: The rats were housed 5 of like sex to a cage. The cages were made of polypropylene (size 38 cm X 56 cm X 18 cm height) and had deteachable wire mesh tops and floors. The cages were suspended on a movable rack.
- Diet: free access to a measured excess amount of food (Labsure LAD 1)
- Water: free access to tap water
- Acclimation period: at least 5 days before the day of exposure

The rats remained in a holding room except for the 4-hour exposure and an overnight post exposure period when the rats in the test group were kept in a ventilated cabinet to allow dispersal of any residual test substance.

ENVIRONMENTAL CONDITIONS (holding area)
- Temperature: within the limits of 18°C to 24 °C
- Relative humidity: withing the range of 35 % to 65%

No further significant information was stated.

Administration / exposure

Route of administration:

inhalation: dust

Type of inhalation exposure:

whole body

Vehicle:

other: clean air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- System of generating particulates/aerosols: A wright dust generator was used to produce a test atmosphere containing the dust of ammonium dimolybdate. The generator is designed to produce and maintain test atmospheres containing dust by suspending material scraped from the surface of a compressed powder in a stream of dry air.

- Exposure apparatus: Whole-body exposure chambers of square section made of perspex, an internal volume approximately 120 l. For exposure the rats were held in cages of stainless steel mesh partitioned to provide 10 individual animals compartments.

- Source and rate of air: A supply of clean dried compressed air was connected to the dust generator and the supply pressure was adjusted to give a flow rate of 25 litres per minute measured at the generator outlet nozzle.

The control group was treated similarly but received clean air only for 4 hours. The control rats were returned to the holding room at the end of the exposure procedure.

- Method of particle size determination: Two air samples were taken using a Marple 296 cascade impactor. The contents of the stages were weighed to determine the particle size distribution of ammonium dimolybdate in the atmosphere. The air sample was taken at a flow rate of 2.0 litres per minute and the cut-points for the stages of the Marple impactor at this flow rate were 0.52, 0.93, 1.55, 3.5, 6.0, 9.8 µm aerodynamic diameter.

- Temperature, humidity: The air temperature in the exposure chamber was measured with a mercury-in-glass thermometer. The chamber mean air temperatures and the standard deviations (SD) of the means were: Control group: 25 °C (SD= 0.7); test group: 25°C (SD = 0.7). There was no difference in air temperature between the control and test group.
The concentration of water vapour in the chamber air was monitored using an Analytical Development Co. Ltd., water vapour analyser, model 225. The relative humidity was calculated from the recorded data for the water vapour content and temperature of the chamber air. The mean relative humidity of the chamber air and the standard deviation (SD) of the mean during the exposure was: Control group: 51 % RH (SD= 5.6); test group: 56 %RH (SD = 5.6). The small difference in RH between the control and test groups was considered not to have influenced the results of the study.

TEST ATMOSPHERE (concentration of test substance)
Five air samples were taken from the chamber during the exposure.
Each air sample was withdrawn through a weighed glass fibre filter (Whatman GF/A) held in an open face filter holder, at a rate of 4 litres/minute. The volume of the air sample was measured with a wet-type gas meter. The filters were reweighed to determine the concentration of test substance in the chamber air.

- Particle size distribution: On average, 23 % of the dust collected was 3.5 µm or less in aerodynamic diameter.
- MMAD: 6.3 µm (GSD = 2.75)

No further significant information on inhalation exposure were stated.

Analytical verification of test atmosphere concentrations:

yes

Remarks:

see "details on inhalation exposure" above

Duration of exposure:

4 h

Concentrations:

The mean actual concentration of ammonium dimolybdate was 2.08 mg/l. The variation in concentration (range of values x 100/mean) was 24 % and within acceptable limits. The concentration of 2.08 mg/L was the highest that was practically achieveable as a stable test atmosphere.

No. of animals per sex per dose:

Control group: 5 males / 5 females
Test group: 5 males/ 5 females

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 14 days

- Frequency of observations and weighing: The rats were observed continuously for signs of reaction to the test substance during exposure and at least twice daily throughout the observation period. All rats were weighed daily from the day of delivery to the Huntingdon Research Centre until the end of the observation period.

- Necropsy of survivors performed: yes

- Other examinations performed: The amount of food and water consumed by each cage of rats was measured daily from the day following arrival. The daily mean intakes of food and water for each rat were calculated from the recorded data.
At the end of the 14-day observation period, the rats were anaesthetised by intraperitoneal injection of pentobarbitone sodium and killed by exsanguination.
The rats were subjected to a detailed macroscopic examination. The lungs were removed, dissected clear of surrounding tissue and weighed in order to calculate the lung weight to bodyweight ratio.
The lungs were infused with, and preserved in, buffered 10 % formalin together with samples of the liver and kidneys.
The fixed lungs were embedded in paraffin wax and processed routinely. Four-micron sections were prepared, stained with haematoxylin and eosin and examined under the light microscope.
The liver and kidneys were preserved.

Statistics:

not required.

Results and discussion

Effect levels

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 2.08 mg/L air

Exp. duration:

4 h

Mortality:

There were no deaths during the study.

Clinical signs:

other: During exposure: Partial closing of the eyes, wetness around the mouth, restless behaviour and the adoption of a hunched body posture were the main signs seen in rats exposed to ammonium dimolybdate. These signs were considered to be consistent with expos

Body weight:

Small losses in bodyweight or a reduced rate of bodyweight gain were observed in rats exposed to ammonium dimolybdate for 2-3 days following exposure. Subsequently the rate of weight gain was similar to that of the control rats.

Gross pathology:

Macroscopic pathology:
There were no macroscopic abnormalities in any of the rats.
Microscopic pathology:
No treatment -related changes were observed.

Other findings:

- Organ weights: The lung weight to bodyweight ratio was considered to be within normal limits for all rat.
- Other observations:
Food consumption was slightly reduced for 2 days following exposure. Subsequently, food consumption for exposed rats was similar to that for the control rats. Water consumption was increased on Days 3 and 4 in male exposed rats. There was no clear effect of exposure in female rats. The water consumption for female control rats was higher than normal. The reason for this is not known.

Applicant's summary and conclusion

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU