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Acute Toxicity: inhalation

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Administrative data

Endpoint:
acute toxicity: inhalation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study with acceptable restrictions. Only tested up to 1 mg/L, only 6 males tested. Secondary source.

Data source

Reference
Reference Type:
publication
Title:
Comparative inhalation hazards of aluminium and brass powders using bronchopulmonary lavage as an indicator of lung damage.
Author:
Thomson, S.M. et al.
Year:
1986
Bibliographic source:
J Appl Toxicol 693: 197-209

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 403 (Acute Inhalation Toxicity)
Deviations:
yes
Remarks:
: only tested up to 1 mg/L, only 6 males tested. Secondary source.
Principles of method if other than guideline:
The purpose of the study was “to compare the acute inhalation toxicity of aluminium and brass dust utilizing pulmonary lavage analyses correlated with physiological measurements and pathological evaluation as a criteria for lung injury”. Two experiments were conducted: one with observations at 24 hours and 14 days post-exposure, the other with additional groups observed at 3 and 6 months post-exposure, in order to examine longer term effects of the acute exposure.
GLP compliance:
not specified
Test type:
standard acute method
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Name: Aluminium flake Reynolds 40xD
Supplier: Reynolds Metal Co., Richmond, VA
Purity: 99.0%
Batch Number: not reported
Storage: Not reported (NR).
Levels of impurities:
Analysed by AAS –
Cu, Zn, Be, Ni: below detection limit
Fe: 0.6%
Pb: 0.3%
Sn: 0.09%
Sb: 0.2%
Cr: 0.2%
As: 0.03%
Physical description: irregularly shaped
-Note: coated with <2% palmitic and stearic acids to facilitate the milling process in manufacture.

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: No data
- Age at study initiation: 10 – 12 weeks
- Weight at study initiation: The animals were weighted but the weights were not reported.
- Housing: Following exposure, the animals were placed in individual, stainless steel suspended cages.
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22±2ºC
- Humidity (%):40 - 60%

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
whole body
Vehicle:
other: Not relevant.
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Metronics Model #3 aerosol generator.
- Exposure chamber volume: The first experiment (observations at 24h and 14 days post-exposure) used a chamber of 3000 litre volume. The chamber used for the longer term aluminium exposures was 1000L in volume.
- Temperature, humidity, pressure in air chamber: The temperature in the chamber was maintained at 22ºC±2ºC and the humidity between 30 and 70%.


TEST ATMOSPHERE (if not tabulated)
- Particle size distribution: The particles were irregularly shaped. The average MMAD for the brass powder was 1.82 µm, the geometric mean particle size was 1.72 µm and for the aluminium powder the MMAD was 1.58 µm and the geometric mean particle size was 1.91 µm.

- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.):
To determine the particle size, samples of the metal flakes were collected on cellulose ester filters cleared and examined under the microscope.

The mass median aerodynamic diameter (MMAD) of each compound was also measured using a Sierra cascade impactor (model #2210-1C).


Details on analytical verification of doses or concentrations:
To verify the test atmosphere concentrations, vacuum sampling with appropriate volumes of chamber air was performed five times during the exposure period (at 10, 60, 120, 180 and 220 minutes). The levels of test materials were determined gravimetrically.

Frequency of treatment/exposure:
Single.



Analytical verification of test atmosphere concentrations:
yes
Remarks:
To verify the test atmosphere concentrations, vacuum sampling with appropriate volumes of chamber air was performed five times during the exposure period (at 10, 60,120, 180 and 220 minutes). The levels of test materials were determined gravimetrically
Duration of exposure:
4 h
Concentrations:
10, 50, 100, 200 and 1000 mg/m³ nominal (corresponding to 9.16, 47.3, 111, 206 and 888 mg/m³, determined gravimetrically)
No. of animals per sex per dose:
6 males
Control animals:
yes
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: The animals were weighed at weekly intervals during the experimental and post-exposure periods.
- Necropsy of survivors performed: yes
- Other examinations performed: total body weight, organ weight (heart, lung, kidneys, gonads), gross and microscopic pathology of nasal air passages, trachea, lungs and hilar lymph nodes






Statistics:
The t-test was used to carry out inter-group comparisons.

Results and discussion

Effect levelsopen allclose all
Sex:
male
Dose descriptor:
LC0
Effect level:
0.888 mg/L air (analytical)
Based on:
test mat.
Exp. duration:
4 h
Remarks on result:
other: (nominal: 1 mg/L) Slope: could not be calculated.
Sex:
male
Dose descriptor:
LC50
Effect level:
> 0.888 mg/L air (analytical)
Based on:
test mat.
Exp. duration:
4 h
Remarks on result:
other: Corresponding to >888 mg/m³ air
Sex:
male
Dose descriptor:
other: NOAEC
Effect level:
10 mg/m³ air
Based on:
test mat.
Exp. duration:
4 h
Mortality:
No deaths were reported.
Clinical signs:
other: The authors report (qualitatively) that none of the rats exposed to aluminium flakes were adversely affected.
Body weight:
The authors reported (qualitatively) that even the highest dose group (1000 mg/m³) gained weight at the same rate as the controls.
Gross pathology:
Black particulate matter was seen on the luminal surface of terminal airways.
Other findings:
Pulmonary function
These results were reported qualitatively. The authors reported no adverse pulmonary physiological response even at the highest concentration (1000 mg/m3).

Bronchopulmonary lavage
The cytology results from these examinations were provided in a table as the mean (±SD) of the measurements from the six animals in each group. No significance testing was included.

The levels of protein and enzymes in the lung lavage fluid were presented as graphs with significant differences between treatment and control indicated.

Cytology
Polymorphonuclear neutrophils did not differ between the control and exposed groups at the 10mg/m3 level at 24h or 14 days. A small difference was evident at 14 days but was attributable to levels in only one rat.
- increases in PMN were observed at all other doses and timepoints.
- increases in total nucleated cells were observed at 100, 200 and 1000 mg/m3 for all timepoints. The highest values were observed in most cases at 14 days.

Biochemical analyses - (treatment versus control, t-test, significance – p<0.05)
Total protein
10 mg/m3: not statistically significant , all timepoints
50 mg/m3: ns, all timepoints
100 mg/m3: increase (factor of 3) at 14 days
200 mg/m3: increase at 24 h, 14 d, 3 mths (factor of 3)
1000 mg/m3: increase at 24 h, 14 d, 3 mths (factor of 3)

- No consistent dose response.

LDH: (treatment versus control, t-test, significance – p<0.05)
10 mg/m3: ns, all timepoints
50 mg/m3: ns, all timepoints
100 mg/m3: increase (factor of 1.5 to 2) at 24h, 14d, 3 mths.
200 mg/m3: increase at 24 h, 14 d, 3 mths (factor of 2 to 4)
1000 mg/m3: increased at 24 h, 14 d, 3 mths (factor of 2 to 4)

- Some evidence of dose response.

ALKP: (treatment versus control, t-test, significance – p<0.05)
10 mg/m3: ns, all timepoints
50 mg/m3: increase (factor of 1.5) at 24h, 14 d, 6 mths
100, 200 and 1000 mg/m3: increase (factor of 2) at 24h, 14d, 3 mths.

- Limited dose response

G6PD: (treatment versus. control, t-test, significance – p<0.05)
10, 50, 100, 200 mg/m3: all ns
1000 mg/m3: increase (factor of 1.5 to 2) at 24h and 14d, ns at 3 mths.

Pathology/histology
24h: little cellular response was observed even in the 1000 mg/m3 dose group;
14 d: prominent hystiocytic cellular response with alveolar macrophages containing Al particulates; the 200 and 1000 mg/m3 dose groups had microgranulomas in terminal airways and alveolar septae;
3 and 6 mths: aluminium flake was still present in microgranulomas in alveolar walls; hilar lymph nodes contained numerous small histiocytic aggregates that contained particulate material.

Applicant's summary and conclusion

Interpretation of results:
not classified
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
No mortality was observed even at the highest aluminium flake concentration. No toxic signs were observed and there were no changes in measurements of lung function. At concentrations above 10 mg/m³, an increase in polymorphonuclear neutrophils in the bronchoalveolar lavage at 24 hours was typical of a mild acute inflammatory response. Increases in lactate dehydrogenase, alkaline phosphatase and total protein that persisted to 3 months provide evidence for a chronic irritant response in the presence of insoluble flakes retained in the lungs. These changes were also not observed at the lowest dose level, 10 mg/m³. Multifocal microgranulomas were observed in terminal airways and alveolar septae in the 200 and 1000 mg/m³ dose groups at 14 days, 3 months and 6 months. Black particulate material was observed in the hilar lymph nodes at 14 days and beyond, consistent with clearance by alveolar macrophages. The acute inflammatory response to aluminium flakes was less dramatic than those for more soluble brass dust. The brass dust, however, did not exhibit evidence of a chronic irritant response, effects were resolved by 14 days post-exposure with the exception of larger numbers of alveolar macrophages around terminal airways which had resolved by 3 months. Brass particulate matter was not found in the lavage fluid nor in histopathological examinations.
Executive summary:

Thomson et al. (1986) conducted a study in male Fischer 344 rats (10-12 weeks old) to investigate and compare the acute inhalation toxicity of aluminium flake and brass flake dusts. Both were irregularly shaped flake dusts coated with <2% palmitic and stearic acids to facilitate the milling process in manufacture. Two experiments were conducted: one with observations at 24 hours and 14 days post-exposure, the other with additional groups observed at 3 and 6 months post-exposure, in order to examine longer term effects of the acute exposure. The animals were exposed to the dust for 4 hours. During the exposure period, the animals were placed in compartmentalized wire cages without food, water or bedding in temperature - (22 ºC±2 ºC ) and humidity - (30 to 70%) controlled chambers. The test atmospheres were produced using a Metronics Model #3 aerosol generator. Nominal concentrations for the aluminium powder were 10, 50, 100, 200 and 1000 mg/m³. The corresponding concentrations determined gravimetrically were 9.16, 47.3, 111, 206 and 888 mg/m³.  The MMAD for the aluminium powder was 1.58 µm (geometric mean diameter from microscopic analysis=2.82 ±0.26 µm). All animals were examined for toxic signs before and after exposure and daily during the post-exposure period. The animals were weighed at weekly intervals during the experimental and post-exposure periods. Pulmonary function measurements were conducted at 24 hours, 14 days, 3 months and 6 months post-exposure. Bronchopulmonary lavage was conducted and the BALF analysed for total cell counts, differential cell counts, and biochemical parameters (total protein and levels of glucose-6-phosphate dehydrogenase (G-6-PD), lactate dehydrogenase (LDH), and alkaline phosphatase (ALKP)).  Blood samples were also collected by cardiac puncture at each timepoint post-exposure for the analysis of copper, zinc, and aluminium.  After blood collection, rats were necropsied and the following examinations performed: total body weight, organ weight (heart, lung, kidneys, gonads), gross and microscopic pathology of nasal air passages, trachea, lungs and hilar lymph nodes. No mortality was observed even at the highest aluminium flake concentration. No toxic signs were observed and there were no changes in measurements of lung function even at the highest dose (1000mg/m³).  At concentrations greater than 10 mg/m³, an increase in polymorphonuclear neutrophils in the bronchoalveolar lavage was observed at 24 hours, typical of a mild acute inflammatory response. Increases in lactate dehydrogenase, alkaline phosphatase and total protein that persisted to 3 months provide evidence for a chronic irritant response in the presence of insoluble aluminium flakes retained in the lungs. These changes were not observed at the lowest dose level, 10 mg/m³. Multifocal microgranulomas were observed in terminal airways and alveolar septae in the 200 and 1000 mg/m³dose groups at 14 days, 3 months and 6 months. Black particulate material was observed in the hilar lymph nodes at 14 days and also later timepoints suggesting clearance by alveolar macrophages. The acute inflammatory response to aluminium flakes was less dramatic than those for more soluble brass dust. The brass dust, however, did not exhibit evidence of a chronic irritant response, effects were resolved by 14 days post-exposure with the exception of larger numbers of alveolar macrophages around terminal airways which had resolved by 3 months. Brass particulate matter was not found in the lavage fluid or in histopathological examinations. The 4 hour exposure period conforms with acute inhalation toxicity guidelines. The use of only one sex of animals and the dose levels were adequately justified. Concentrations were analytically verified and sufficient numbers of animals were used. The results from lung function measurements were not provided in the publication and the highest dose was not intended to allow estimation of the LC50.