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Acute Toxicity: inhalation

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acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2010-06-14 to 2010-06-28
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study reliable without restrictions

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
OECD Guideline 403 (Acute Inhalation Toxicity)
Version / remarks:
, 2009-09-07
A target concentration of 5.5 mg/l was used instead of 5 mg/L (the upper limit of the guideline was increased with 10% in order to avoid the mean actual concentration to fall below the cut off value due to experimental variation)
GLP compliance:
Test type:
standard acute method
Limit test:

Test material

Constituent 1
Reference substance name:
Strontium nitrate
EC Number:
EC Name:
Strontium nitrate
Cas Number:
strontium dinitrate
Test material form:
solid: crystalline
Details on test material:
- Name of test material (as cited in study report): Strontium nitrate
- Molecular formula: Sr(NO3)2
- Molecular weight: 211.63
- Physical state: White crystals
- Storage condition of test material: At room temperature in the dark
- Stability under storage conditions: Stable
- pH (1% in water, indicative range): 6.4 - 7.0 (determined at NOTOX)
- Stability in vehicle water: not indicated
- Solubility in vehicle water: Yes
No further information on the test material was stated.

Test animals

Details on test animals or test system and environmental conditions:
- Source: Charles River Deutschland, Sulzfeld, Germany.
- Age at study initiation: Approximately 11 weeks old
- Weight at study initiation: Males: 296 - 320 g; Females: 197 - 217 g
- Housing: Before exposure: Group housing of five animals per sex per cage in labelled Macrolon cages (type IV; height 18 cm) containing sterilised sawdust as bedding material (Litalabo, S.P.P.S., Argenteuil, France) and paper as cage-enrichment (Enviro-dri, Wm. Lillico & Son (Wonham Mill Ltd), Surrey, United Kingdom); After exposure: Group housing as before exposure, except that a paper sheet was introduced into the cage covering the bedding and cage enrichment to prevent suffocation in case of bad health condition. At the end of the Day of exposure the paper sheet was removed.
- Diet (ad libitum except during exposure to the test substance): Pelleted rodent diet (SM R/M-Z from SSNIFF® Spezialdiäten GmbH, Soest, Germany)
- Water (ad libitum except during exposure to the test substance): Tap water
- Acclimation period: At least 5 days before start of treatment

- Temperature: 21.0 ± 3.0°C (actual range: 19.8 – 21.5°C)
- Relative humidity: 40-70% (actual range: 39 - 78%)
- Air changes: Approximately 15 air changes per hour
- Photoperiod (hrs dark / hrs light): 12/12
No further information on the test animals was stated.

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
nose only
other: water
Details on inhalation exposure:
- Exposure apparatus: The design of the exposure chamber is based on the flow past nose-only inhalation chamber (Am. Ind. Hyg Assoc. J. 44(12): 923-928, 1983). The chamber consisted of three animal sections with eight animal ports each. Each animal port had its own atmosphere inlet and exhaust outlet. The animals were placed in restraining tubes and connected to the animal ports (20 min. after the last animal was placed the generation of the test atmosphere was started). The number of animal sections and number of open inlets were adapted to the air flow in such a way that at each animal port the theoretical air flow was at least 1 L/min, which ensures an adequate oxygen supply to the animals. The main inlet of the test atmosphere was located at the top section and the main outlet was located at the bottom section. The direction of the flow of the test atmosphere guaranteed a freshly generated atmosphere for each individual animal. All components of the exposure chamber in contact with the test material were made of stainless steel, glass, rubber or plastic. To avoid exposure of the personnel and contamination of the laboratory the exposure chamber was placed in a fume hood, which maintained at a slight negative pressure.

- Test substance preparation: A 60 % formulation was prepared within 4 hours prior to dosing. Homogeneity was accomplished to a visually acceptable level

- System of generating particulates/aerosols: An aerosol was generated by nebulization of the test substance by means of a nebulizer (type 950, Hospitak Inc., Lindenhurst, NY, USA) (appendix 1, figure 1). The primary aerosol was diluted with pressurized air before it entered the exposure chamber. The mean total airflow was 12 L/min.

- Method of particle size determination: The droplet size distribution was characterized twice during the exposure period. The samples were drawn (2 L/min) from the test atmosphere through a tube mounted in one of the free animal ports of the middle section of the exposure chamber. The samples were collected with an 8 stage Marple personal cascade impactor containing fiber glass filters (SKC 225-713, glass fiber, SKC Omega Specialty Division, Chelmsford, MA, USA) and a fiber glass back-up filter (SEC-290-F1, Westech, Upper Stondon, Bedfordshire, England). Amounts of test substance collected were measured gravimetrically. Subsequently the Mass Median Aerodynamic Diameter (MMAD) and the Geometric Standard Deviation (GSD) were determined.

- Treatment of exhaust air: From the exposure chamber the test atmosphere was passed through a filter before it was released to the exhaust of the fume hood.
- Temperature, humidity, pressure in air chamber: The temperature and relative humidity were measured with a humidity and temperature indicator (E+E Elektronik, Engerwitzdorf, Austria) and were recorded after the animals were placed in the experimental set-up and at 30 minute intervals after initiation of the exposure. The temperature of the atmosphere was between 20.4 and 20.7°C and relative humidity was between 69 and 76%.

- Nominal concentration: The nominal concentration was calculated by dividing the amount of test substance used by the volume of pressurized air (average air flow times exposure time) entering the exposure chamber used for exposure of the animals.

- Brief description of analytical method used: The actual concentration was determined nine times during the exposure period. Samples were drawn from the test atmosphere through a tube mounted in one of the free animal ports of the middle section of the exposure chamber. Samples were drawn through a glass fiber filter (type APFC04700, Millipore, Billerica, MA, USA). The filters were placed in a stove at 70ºC for 3 minutes before weighing to allow the water to evaporate. The collected amount of test substance in the air sample (before and after drying the filters) was measured gravimetrically. Sample volumes were measured by means of a dry gas meter (type G 1.6, Actaris Meterfabriek B.V., Dordrecht, The Netherlands).

- Samples taken from breathing zone: yes

-Stability monitoring: The opacity of the test atmosphere was monitored by means of a real time aerosol monitoring system (Windust Pro, Casella, Amherst, NH, USA). Data obtained with this system were used to illustrate the stability of the aerosol during exposure of the animals.
Data obtained from the opacity monitor showed that the aerosol was sufficiently stable

VEHICLE - Water (Elix, Millipore S.A.S., Molsheim, France)
- Justification of choice of vehicle: The vehicle was selected based on trial formulation performed at NOTOX and on test substance data supplied by the sponsor.

TEST ATMOSPHERE (if not tabulated)
The MMAD and GSD were determined twice:
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.):
Measurement 1: MMAD: 3.4 µm (GSD = 1.8)
Measurement 2: MMAD: 3.7 µm (GSD = 2.1)
No further information on the inhalation exposure was stated.
Analytical verification of test atmosphere concentrations:
See "Details on inhalation exposure" above
Duration of exposure:
4 h
Nominal concentration: 10.1 mg/L
Mean actual concentration: 4.5 +/- 0.6 mg/L
The actual and nominal concentrations were corrected for water content of the formulation. The generation efficiency (ratio of actual and nominal concentration) was 10%.
No. of animals per sex per dose:
5 males / 5 females
Control animals:
Details on study design:
- Duration of observation period following administration: 15 days
- Observations and weighing: Mortality/Viability was observed twice daily. The time of death was recorded as precisely as possible. Clinical signs (mortality, behavioural signs of distress and effect on respiration) were observed three times during the exposure. Clinical signs were also observed after exposure. These observations were made at 1 and at 3 hours after exposure on the day of dosing (day1) and once daily thereafter, until day 15. The symptoms were graded according to fixed scales and the time of onset, degree and duration were recorded:
Maximum grade 4: grading slight (1) to very severe (4)
Maximum grade 3: grading slight (1) to severe (3)
Maximum grade 1: presence is scored (1).
Body weight was measured on Days 1 (pre-administration), 2,4 8 and 15.

- Necropsy of survivors performed: Yes
The animals surviving to the end of the observation period were sacrificed by an intraperitoneal injection with Euthasol ® (AST Farma BV, Oudewater, The Netherlands). All animals assigned to the study were subjected to necropsy and descriptions of all internal macroscopic abnormalities were recorded. Particular attention was given to any changes in the respiratory tract.
No further information on the study design was stated.
No statistical analysis was performed.

Results and discussion

Effect levels
Key result
Dose descriptor:
Effect level:
> 4.5 other: mg/l water (analytically verified)
Based on:
test mat.
Exp. duration:
4 h
Remarks on result:
other: Standard deviation: 0.6 mg/l
One male was found dead approximately 2 hours after start of exposure. No further mortality occurred.
Clinical signs:
other: Laboured respiration was observed for two males between approximately 1.5 and 3.5 hours after start of exposure, including the male that was found dead. Hunched posture, lethargy, rales, gasping, piloerection, chromodacryorrhoea and/or ptosis were observ
Body weight:
Body weight gain of surviving males and females was within the range expected for rats of this strain and age used in this type of study.
Gross pathology:
No abnormalities were found at macroscopic post mortem examination of the animals.
Other findings:
No data

Applicant's summary and conclusion

Interpretation of results:
not classified
Migrated information Criteria used for interpretation of results: EU
The inhalatory LC50, 4h value of strontium nitrate in Wistar rats was considered to be 4.5 +/- 0.6 mg/l.
Based on these results Strontium Nitrate does not have to be classified and has no obligatory labeling requirement for acute inhalation toxicity according to the Globally Harmonized System of Classification and Labeling of Chemicals (GHS) of the United Nations (2007) and Regulation (EC) No 1272/2008 on classification, labelling and packaging of substances and mixtures.
According to the criteria specified by Directive 67/548/EEC and subsequent regulations, the test item is not classified as acute toxic by the inhalation route.