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Acute Toxicity: inhalation

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acute toxicity: inhalation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: acceptable, well-documented publication which meets basic scientific principles.

Data source

Reference Type:
Inhalation Toxicity Studies with Boron Trifluoride.
Rusch, G.M., Hoffman, G.M., McConnell, R.F., Rinehart, W.E.
Bibliographic source:
Toxicology and Applied Pharmacology 83, 69 - 78

Materials and methods

Test guideline
equivalent or similar to
OECD Guideline 403 (Acute Inhalation Toxicity)
GLP compliance:
not specified
Test type:
standard acute method
Limit test:

Test material

Details on test material:
Name of the test substance: boron trifluoride dihydrate (63.87% BF3)

Test animals

Fischer 344
Details on test animals and environmental conditions:
- Source: Charles River Breeding Labs (Portage, Mich.)
- Age at study initiation: approximately 7 weeks old
- Weight at study initiation: no data
- Fasting period before study: no
- Housing: individually in suspended stainless-steel mesh cages
- Diet (e.g. ad libitum): ad libitum Purin Rat Chow 5001
- Water (e.g. ad libitum): ad libitum
- Acclimation period: for a minimum of 2 weeks


Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
whole body
other: air
Details on inhalation exposure:
Exposure Chamber Designs and Operation
The acute exposure was conducted in 225-liter stainless-steel and glass exposure chambers, operated under negative pressure with filtered, conditioned air.
The total flow rate during the acute study was approximately 50 liters/min, providing a t99 equilibration time of 21 min.

Test Atmosphere Generation Procedures
Test atmospheres in the acute study were generated with a Solo-Sphere nebulizer (McGraw Respiratory Therapy, Irvine, CA.) operated with compressed, breathing-grade air. Exposure concentrations were controlled by regulating the airflow through the nebulizer, and thus the rate of aerosol generation.

Analysis of Chamber Concentrations
Nominal aerosol concentrations were determined daily by measuring the amount of test material consumed during the exposure and dividing this by the total airflow through the chamber. At hourly intervals, actual air concentration measurements were made by trapping aerosol samples of known volume in I5-ml impingers, using a flow-Gmiting orifice (Millipore XX50000014) with a pump (Gast DOA-122) and dry test meter (Singer DTM-115-3) for volume measurement. The aerosol was then dissolved in distilled water and analyzed for BF3 content by an ion-selective electrode technique. Sample volumes were varied to permit collection of roughly equal quantities of BF3.
Particle size measurements were made with an Anderson I ACFM particle sizing sampler (Anderson 2000, Inc., Atlanta, Ga.). Measurements were performed hourly during the acute exposures; three times/week during the subacute exposures; and twice each week during the subchronic exposures. The material collected on each stage was determined gravimetrically.
Mass median aerodynamic diameter: 1.8 µm
Analytical verification of test atmosphere concentrations:
Duration of exposure:
4 h
1010, 1220, 1320, 1540 mg boron trifluoride dihydrate/m3 (= 1.01, 1.22, 1.32 or 1.54 mg/l)
No. of animals per sex per dose:
Control animals:
Details on study design:
Animals were observed at 15-min intervals during the first hour of exposure, at hourly intervals for the remaining 3 hr of exposure, for the first 4 hr following exposure, and daily for 14 days post-exposure for mortality (twice daily) and clinical signs of toxicity. Individual body weights were recorded on the day of exposure (prior to exposure) and on days 1, 2, 4, 7, and 14 following exposure.
Gross necropsy examinations were conducted on all animals.
Four groups of rats were separately exposed for 4 hr to aerosols of boron trifluoride at concentrations of 1.54, 1.32, 1.21, 1.01 mg/liter. The approximate mass median aerodynamic diameter of the aerosol was 1.8 um with a geometric standard deviation of 1.9.

Results and discussion

Effect levels
Dose descriptor:
Effect level:
1.21 mg/L air
Exp. duration:
4 h
9/10 at 1.54 mg/l
8/10 at 1.32 mg/l
2/10 at 1.22 mg/l
3/10 at 1.01 mg/l
Clinical signs:
Clinical signs elicited by the exposures included dry and moist rales, gasping, excessive, oral and nasal discharge, and lacrimation, indicative of respiratory distress and irritation. Recovery was apparent for the rats surviving beyond 6 days postexposure.
Body weight:
Depression of body weight was noted.
Gross pathology:
Increased liver and kidney weights

Applicant's summary and conclusion

An LC50 of 1.21 mg/l or 1210 mg/m3 was calculated for a 4-hr exposure to boron trifluoride dihydrate. The animals exhibited clinical signs of oral and nasal discharge, gasping, lacrimation, indicative of irritation and respiratory distress. Recovery was apparent for the rats surviving beyond 6 days post-exposure.