Registration Dossier

Administrative data

acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03 February 2005 - 15 March 2005
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant study conducted in accordance with international guidelines.

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:
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
Trisilicon tetranitride
EC Number:
EC Name:
Trisilicon tetranitride
Cas Number:
Molecular formula:
Test material form:
solid: particulate/powder
migrated information: powder
Details on test material:
- Name of test material (as cited in study report): SILICON NITRIDE Si3N4
- Physical state: Grey powder
- Analytical purity: >97%
- Lot/batch No.:2607/04-FS
- Storage condition of test material: In closed container

Test animals

Details on test animals or test system and environmental conditions:
- Age at study initiation: 8 to 9 weeks at time of administration.
- Weight at study initiation: The mean body weights at the day of the exposure were 279 g for males and 220 g for females.
- Housing: Single caging in Makrolon cages type III (39 cm x 23 cm x 18 cm). Wire mesh lids.
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): Tap water from an automatic watering system, ad libitum
- Acclimation period: 5 days

- Temperature (°C): 21.8 - 22.9
- Humidity (%): 47.0 - 55.6
- Air changes (per hr): 12
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
Type of inhalation exposure:
nose only
Details on inhalation exposure:
- Exposure apparatus: TSE, Technical & Scientific Equipment GmbH, Kronberg, Germany; article no. 504101. The apparatus was 30 cm in diameter
and 27 cm in height. In the twenty openings of the outer chamber, the inhalation tubes with the animals were situated. As only ten animals were
administered, only the openings in the upper row were used.
Neither feed nor water was offered to the animals during the exposure.
- Exposure chamber volume: 19 L
- Source and rate of air: The air was obtained from a central pressure pump. The relative humidity was reduced to about 10 0/0. The air was filtered oil-free and distributed within the Research Center. In the Toxicology Department the pressure was reduced to 3 bar.The air was partly sucked up by a tube system within the outer chamber, the rest escaped via the upper central opening and via the animal tubes.
- Temperature, humidity, pressure in air chamber: Temperature: 20.4 to 21.6°C. The relative humidity: 15.8 to 27.4%

- Brief description of analytical method used: The test substance was stirred in the dust generator to prevent agglomeration. It was trickled
on to an adjustable vibratory metering system. From there it fell into the aerosol flask, was picked up by an air flow and transported to the lower center of the inhalation chamber.
Larger particles sedimented within the inner chamber room and smaller ones followed the air stream to the outer chamber and reached the
animals. The vibratory metering system was adjusted to get a dust concentration of about 5 mg/L.
The air flow was 700 I per hour. Larger particles, about 75 % of the test substance, were caught in the inner chamber by sedimentation. Smaller particles, about 25 % of the test substance, reached the outer chamber and the inhalation tubes.

TEST ATMOSPHERE (if not tabulated)
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): 1.7µm/ 2.2 (91 % of the mass was in the fraction with a diameter of less than 5µm)
-Particle size distribution: The size of the dust particles was analysed with a cascade impactor. It contains nine steps with cut-offdiameters
from 0.06 IJm to 16 IJm. The cut-off diameters were obtained from the manufacturer.
Analytical verification of test atmosphere concentrations:
Duration of exposure:
4 h
5.07 mg/L air
No. of animals per sex per dose:
Control animals:
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Behaviour, reactions and physical signs of each of the animals were observed 1, 2, 3, 4, 5
and 6 hours after the start of exposure and then at least once a day for a total of 2 weeks. The individual body weight of each animal was determined before administration, 7 days p.a. and 14 days p.a.
Body weight gain was calculated for each week of the study, Le. between 0 and 7 d p.a. and between 7 and 14 d p.a.
- Necropsy of survivors performed: yes
As a limit test was performed, no calculation of the LC50 was possible.

Results and discussion

Preliminary study:
Two rats were exposed during the preliminary experiments to obtain an assessment of the useful concentration range.
It was tried to produce a dust with an actual concentration of more than 5 mg test substance per litre.

The production of a dust was first tried with a dust generator RBG 1000 from Palas® GmbH, Karlsruhe, Germany. In this generator the test substance is pressed out of a storage vessel by a piston, scratched by a brush and nebulised. Due to the force of the piston, the test substance in the storage vessel increased in density and hardness and after a short time it blocked the brush.
Concentrations of more than about 1 mg/L could therefore not generated with this dust generator.

Two rats were exposed for 4 hours to the test substance dust of about 1 mg/L. The animals survived without any toxic signs.
Therefore the generation of the dust was tried with the dust generator from Technical & Scientific Instruments GmbH, Kronberg, Germany. Here the test substance is not pressed by a piston.
With this generator it was possible to produce a dust concentration of 5 mg/L, but the test substance formed - although it was stirred - lumps in the storage vessel and the output was therefore not very constant. It also happened some times that the nebulisation orifice was blocked by the test substance, but the block could be removed quickly and easily with a wire.
It was therefore decided to use the dust generator from Technical &Scientific Instruments GmbH for the main experiment and try to produce a dust concentration of 5 mg/L.
Because of the maybe not constant output it was decided to measure the actual dust concentration 16 times during the 4 hour administration.
Effect levels
Dose descriptor:
Effect level:
> 5.07 mg/L air
Based on:
test mat.
Exp. duration:
4 h
All animals survived till the end of the study.
Clinical signs:
other: All animals were normal during the 14-day observation period.
Body weight:
The mean body weight gain in the first week after the exposure was 34 g for males and 6 g for females. In the second week males gained 49 g, females 17 g.
One female lost weight in the first week after the exposure.
Other findings:
- Other observations: Nothing abnormal was seen in any of the animals. Males and females responded similarly to the test substance.

Any other information on results incl. tables

The calculated Mass Median Aerodynamic Diameter (MMAD) of the test substance used was 1.7µm. 91% of the mass was in the fraction with a diameter of less than 5µm.

Applicant's summary and conclusion

Interpretation of results:
not classified
Migrated information Criteria used for interpretation of results: EU
The inhalation exposure of rats to "SILICON NITRIDE Si3N4" at a concentration of 5.07 mg/L did not produce toxic signs after the exposure.

The LC50 (inhalation), four hours exposure, of "SILICON NITRIDE Si3N4" for male and female rats is therefore greater than 5.07 mg per litre air.

No classification of "SILICON NITRIDE Si3N4" is derived from the results of this study according to the Directive 2001/59/EC.