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Toxicological information

Acute Toxicity: inhalation

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Administrative data

Endpoint:
acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant, guideline study, unpublished report available, no restrictions, fully adequate for assessment

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1993
Report Date:
1993

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 403 (Acute Inhalation Toxicity)
GLP compliance:
yes
Test type:
standard acute method
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): cryolite
- Colour: white
- Form: powder
- Partie-Nr: 2

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
Animals used in this study were selected from 3 consignments of rats obatined from Charles River UK Limited, Manston Road, Margate, Kent, UK. The rats were selected in a way that males and females would be of similar bodyweight (ca. 200 g) on the day of exposure.
On arrival the rats were allocated by random design to 1 of 4 groups, each of 5 males and 5 females. The rats were housed by sex in groups of 5 and acclimatised to laboartory conditions for at least 5 days prior to exposure.
The holding cages (35 cm x 53 cm x 25 cm height) were made of stainless steel sheet and wire mesh and were suspended on a movable rack. All rats had free access to a measured excess amount of food (SDS RM1) and tap water.
Lighting was artificial for 12 h per day, the temperature (°C) in the holding room was 18-24 and the humidity (%) in this room was: 20-65.

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
whole body
Vehicle:
other: unchanged (no vehicle)
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: a wright dust generator
- Exposure chamber volume: 120 litres, each chamber was divided by wire mesh partitions to provide 10 separate animal compartments
- Method of holding animals in test chamber: whole body chambers
- Source and rate of air: 25 litres per minute
- System of generating particulates/aerosols: a wright dust generator, the test atmosphere contained a particulate aerosol generated from the test substance.
- Method of particle size determination: test atmosphere was passed trough a glass elutriation column
- Temperature, humidity in air chamber: 24 °C, 46,4 % relative humidity in control group, 24 °C and 43.7 % relative humidity in 4.34 mg/l group, 23 °C and 53.0 % relative humidity in 1.33 mg/l group, 24 °C and 49.8 % relative humidity in 2.83 mg/l group.

TEST ATMOSPHERE
- Brief description of analytical method used: an air sample was withdrawn trough a weighed glass fibre filter mounted in an open face filter holder. The filters were removed and re-weighed. Five air samples were taken from the chamber during each exposure.
- Samples taken from breathing zone: yes

TEST ATMOSPHERE (if not tabulated)
- Particle size distribution:
Two air samples were taken during each exposure using a Marple cascade impactor. The material collected on the stages of the sampler was weighed to determine the particle size distribution of cryolite in the test atmospheres.
Particle sizes were as follows:
%<1 µm --> 4.34 mg/l group: 2.2, group 3: 1.4, group 4: 8.2.
Size for 25% (µm) --> 4.34 mg/l group: 2.6, 1.33 mg/l group: 2.5, 2.83 mg/l group: 1.8.
% respirable (6 µm) --> 4.34 mg/l group: 67.9, 1.33 mg/l group: 77.8, 2.83 mg/l group: 78.0.
- MMAD (Mass median aerodynamic diameter) / GSD (geometric st. dev.): 4.34 mg/l group: 4.3, 1.33 mg/l group: 3.8 and 2.83 mg/l group: 3.2 µm.
Analytical verification of test atmosphere concentrations:
yes
Duration of exposure:
4 h
Concentrations:
4.34 (±0.57), 2.83 (±0.25), 1.33 (±0.10) mg/l (mean ± SD)
33.04, 19.03 and 7.79 mg/l (nominal)

MMAD and respirable fraction:
4.34 mg/l: MMAD of 4.3 µm and 67.9 % of respirable particles;
2.83 mg/l: MMAD of 3.2 µm and 78.0 % of respirable particles;
1.33 mg/l: MMAD 3.8 µm and 77.8 % of respirable particles.
No. of animals per sex per dose:
5
Control animals:
yes
Details on study design:
The rats were observed continuously for signs of reaction to the test substance during exposure and at least twice daily during the observation period. The observation period was 14 days, but extended for the highest concentration to 21 days. Body weights, food and water consumption were determined daily. At the end of the observation period surviving rats were killed for macroscopic and microscopic examination.
Statistics:
The concentration of the test substance likely to cause death in 50% of exposed rats following a single 4-hour exposure was calculated by the probit method of Miller and Tainter (Miller, LC and Tainter ML. Proc. Soc. Exp. Bio. Med., 57, 261-264, 1944).

Results and discussion

Effect levels
Sex:
male/female
Dose descriptor:
LC50
Effect level:
4.47 mg/L air (analytical)
Exp. duration:
4 h
Remarks on result:
other: SE is 0.85 mg/L
Mortality:
At the dosage of 4.34 mg/l two male rates were found dead on Day 5. One female rat was found on Day 7. Two male rats were found dead on Day 9 and one male was found dead on Day 10 of the observation period.
At the 2.83 mg/l dosage level one male rat was found dead on Day 4 of the observation period.
Clinical signs:
During exposure: partial closing of the eyes and exaggerated respiratory movements;
During observation period: exaggerated respiratory movements or noisy respiration, lethargy, hypothermia, pilo-erection and a hunched body posture.
Body weight:
There were moderate reductions in the rate of bodyweight gain for up to 3 days in female rats exposed at 1.33 mg/l or 2.83 mg/l of air. At 4.34 mg/l of air there was a delay in weight reduction until days 4-6. Subsequently weight gain was similar tot that of control rats. In male rats there was a slight reduction in bodyweight gain for up to 2 days following exposure at 1.33 mg/l or 2.83 mg/l of air. Male rats exposed at 4.34 mg/l continued to lose weight until the time of death.
Gross pathology:
A high lung weight to bodyweight ratio was found for all rats surviving exposure. The lung to bodyweight ratio for the majority of rats surviving exposure at 1.33, 2.83 or 4.34 mg/l was higher than the control values.
The findings for rats that died as a result of exposure to cryolite were typified by swollen and severe congestion of the lungs.
Other findings:
Food consumption
Reductions in food consumption were observed for up to 10 days in male rats exposed at 2.82 mg/l of air. Male and female rats exposed at 1.33 mg/l and 2.82 mg/l had a reduced consumption for one day following exposure. Male rats exposed at 4.34 mg/l had a reduced food consumption until time of death. Consumption was slightly reduced for 6 days in female rats at 4.34 mg/l and for 3 days in female rats exposed at 1.33 mg/l. Water consumption was variable for most test groups with no markedly reduced level of consumption except for male rats exposed at 4.34 mg/l of air.

Microscopic pathology:
- Lungs; increased alveolar macrophages, with/without alveolar septal fibrosis adjacent to alveolar ducts, sometimes with focal alveolar epithelialisation; alveolar congestion/haemorrhage; and alveolitis.
Prominent goblet cells in the bronchiolar epithelium were recorded in some rats.
Changes seen only in decedent rats included hyaline membranes with/without alveolar oedema, bronchiolar epithelial basophilia and hyperplasia and early thrombus in pulmonary artery. Pleural inflammation was seen in a single decedent rat.
Alveolar macrophages containing brown pigment were seen in a single terminal rat.
- Liver: centrilobular hepatocyte necrosis/degeneration with sinusoidal congestion was seen in ail decedent rats in at the high dose.
Prominent.mitotic frgures were seen in a single rat at the high dose killed at termination.

Applicant's summary and conclusion