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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:
weight of evidence
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Scientific publication, which meets generally accepted scientific standards and is acceptable for assessment.

Data source

Reference Type:
Comparative Inhalation Hazards of Aluminum and Brass Powders Using Bronchopulmonary Lavage as an Indicator of Lung Damage
Thomson, S. M.
Bibliographic source:
Journal of Applied Toxicology Vol; 6( 3): 197-209

Materials and methods

Test guideline
equivalent or similar to
OECD Guideline 403 (Acute Inhalation Toxicity)
, see text box below
Principles of method if other than guideline:
1 mg/L was the maximum tested concentrations. The guideline recommends 2 mg/L as limit dose. The post exposure observation period was in total six months and additional endpoints were investigated to receive further information.
GLP compliance:
not specified
Test type:
standard acute method
Limit test:

Test material

Test material form:
solid: particulate/powder
migrated information: powder
Details on test material:
- Name of test material (as cited in study report): aluminum flakes, dust or powder
- Physical state: powder
- Analytical purity: 99 %
- Impurities (identity and concentrations): 0.6 % Fe, 0.3 % Pb, 0.09 % Sn, 0.2 % Sb, 0.2 % Cr, 0.03 % As

Test animals

Fischer 344
Details on test animals and environmental conditions:
- Age at study initiation: 10-12 weeks
- Fasting: during exposure
- Housing: during exposure: individual in compartimentalized wire cages; after exposure: individual in stainless steel suspended gages
- Diet (e.g. ad libitum): Certified laboratory rodent chow #5002 (Pruina, St Loui, Missouri, USA), ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 2 weeks

- Temperature (°C): 22 +/- 2 °C
- Humidity (%): 40-60 %

Administration / exposure

Route of administration:
inhalation: dust
Type of inhalation exposure:
whole body
not specified
Details on inhalation exposure:
- Exposure chamber volume: 1000 l
- System of generating particulates/aerosols: Metronics Model #3 aerosol generator
- Method of particle size determination: microscopically
- Temperature, humidity: 22 +/- 2 °C, 30-70 % humidity

TEST ATMOSPHERE (if not tabulated)
- Particle size distribution: over 90 % were under 5 µm
- MMAD (Mass median aerodynamic diameter): 1.58 µm, θ g= 1.91.
- By selecting appropriate feed and blower speeds of the generator and the chamber airflow, the appropriate target concentrations were maintained
- Brief description of analytical method used: Analytical concentrations were determined gravimetrically by vacuum sampling an appropriate volume of chamber air at five time points (10, 60, 120, 180 and 220 min) during each exposure.
Analytical verification of test atmosphere concentrations:
Duration of exposure:
4 h
10, 50, 100, 200 and 1000 mg/m³
No. of animals per sex per dose:
6 male rats/dose
Control animals:
Details on study design:
- Duration of observation period following administration: timepoints: 24 h, 14 days, 3 and 6 months
- Frequency of observations and weighing: weighed prior to exposure and then weekly; observation daily before and after exposure
- Necropsy of survivors performed: yes
- Histopathology: As part of these acute inhalation experiments, groups of rats were exposed concurrently with the lavage rats in order to correlate pathological changes with physiological and lavage changes. The rats were necropsied and the animal total body weight and the following organ weights were recorded: heart, lung, kidneys and gonads. Gross and microscopic pathological examination was conducted on the nasal turbinates, trachea, lungs and hilar lymph nodes.

- Physiological evaluations: Pulmonary physiological testing were performed at the designated poste exposure time points with anesthetized rats (40 mg/kg bw pentabarbital). A tracheal catheter was connected to a pneumotachometer for the measurement of respiratory flow. An air-filled esophageal catheter was inserted into the esophagous approximately to the level of the thoracic inlet and was connected to one arm of a Hewlett-
Packard@ differential pressure transducer for the measurement of esophageal pressure. Transpulmonary pressure (the difference between esophageal pressure and airway pressure derived from a lateral tap at the distal end of the endotracheal tube) was used for all calculations. Both flow and pressure signals were processed in a Buxco Electronics@, Inc. Pulmonary Function Computer and the following parameters were recorded on a Buxco Electronics, Inc. Data Logger: flow, tidal volume, transpulmonary pressure, compliance, and resistance.

- Bronchopulmonary lavage: Immediately following the pulmonary measurements, the esophagal catheter was removed and the lavage procedure commenced. The lung washing technique consisted of instilling a calculated volume of normal saline (0.015 mL/g body weight) into the lung and immediately withdrawing the saline until a slight pressure was felt on the syringe plunger. Two lavage washes were done in quick succession. The recovered lavage fluid from both washes was pooled and centrifuged at 300 g for 10 min at 4 °C. Following centrifugation, the fluid was separated
into supernatant and pellet fractions. The pellet was resuspended in 1 ml 50% bovine serum albumin and total cell counts were taken on a ZBI Coulter Counter@. A differential cell count was made using a modified Pap staining method. The supernatant lavage fluid was assayed for total protein with the Bio Rad@Protein Assay and for enzymatic activity of alkaline phosphatase, lactate dehydrogenase and glucose-6 phosphate dehydrogenase

Results and discussion

Effect levels
Dose descriptor:
Effect level:
> 1 mg/L air (nominal)
Based on:
test mat.
Exp. duration:
4 h
Remarks on result:
other: no mortality occurred after a post treatment observation period of up to six months
No mortality was observed.
Clinical signs:
other: No adverse signs of toxicity were observed
Body weight:
No effects on body weight gain
Gross pathology:
see below
Other findings:
24 hours post exposure: little cellular response, but accumulation of black particulate material on the luminal surface of terminal airways
14 days post exposure: a prominent histiocytic cellular response was evident. Many of the alveolar macrophages contained phagocytized particulate material. However, there was a significant amount of black particulate material lying free within alveolar luminar. In the higher dose groups (200 mg/m3 and 1000 mg/m3), microgranulomas containing particulate material expanded the walls of terminal airways and alveolar septae. Intra-alveolar hypercellularity attributable to the histiocytic cellular response had a distinct peribronchiolar orientation, thus warranting a morphololgic diagnosis of bronchiocentric granulomatous pneumonia. Examination of hilar lymph nodes at 14 days PE revealed the presence of black particulate material.
The microscopic changes evident at 14 days PE were still present at 3 and 6 months PE. Black particulate material (aluminum flake) was present in histiocytic alveolar macrophages and within microgranulomas expanding the walls of terminal airways and alveolar septae.

No adverse physiological response was notified

Significant increases in ALKP, protein, LDH and G-6-PD examined at 14 days PE. More importantly, these changes persisted at 3 months post exposure and even at 6 months post exposure in the 50 mg/m3 group held and examined at that late date. The only change in the pulmonary lavage fluid of the 10 mg/m3 exposed rats was a slight increase in ALKP.
Cytological analyses showed an increase in total cells and an influx of polymorphonuclear neutrophils (PMN) after 24 hours post exposure. These changes did not diminish after 14 days, 3 months or 6 months. There were no changes in the lavage fluid of rats exposed to 10 mg/m3 of aluminum powder. The slight increase in PMNs at the 10 mg/m3 exposure level was attributed to increases from one rat.

Applicant's summary and conclusion

Interpretation of results:
practically nontoxic
Migrated information Criteria used for interpretation of results: EU
In an acute inhalation study with Aluminum flakes no mortality occured in male F-344 Fischer rats. Based on the results the LC0 of aluminum powder is greater than 1 mg/L.
Executive summary:

In an acute inhalation toxicity study, 10-12 weeks old male F-344 Fischer rats, 6 males/group, were exposed by whole body inhalation to aluminum powder (99% a.i.) for 4 hours at concentrations of 10, 50, 100, 200 and 1000 mg/m³. Animals were observed 24 hours, 14 days, 3 and 6 months post exposure. No mortality occurred.

Additionally, analyses of the lung lavage fluid revealed a persistent increase in alkaline phosphatase, lactate dehydrogenase, glucose-6 phosphate dehydrogenase and protein after 14 days and beyond. In addition a chronic irritant response was also apparent in the cytological analysis as polymorphonuclear neutrophils increased, followed by an increase in the macrophages, which is a typical sign for an acute inflammatory response. Since no mortality occured during the entire observation period, the LC50 can be considered to be greater than 1 mg/L