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Repeated dose toxicity: inhalation

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Administrative data

Endpoint:
short-term repeated dose toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1989-03-07 to 1989-06-09
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP toxicity study conducted under the US National Toxicology Program (NTP).
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2000

Materials and methods

Test guideline
Guideline:
other: The 16-day study was conducted in compliance with FDA Good Laboratory Practice Regulations (21 CFR, Part 58). In addition, as records from the 16-day study were submitted to the NTP Archives, this study was auditied retrospectively.
Deviations:
no
Principles of method if other than guideline:
The 16-day study was conducted in compliance with FDA Good Laboratory Practice Regulations (21 CFR, Part 58). In addition, as records from the 16-day study were submitted to the NTP Archives, this study was auditied retrospectively by an independent quality assurance contractor. Seperate audits covered completeness and accuracy of the pathology data, pathology speciems, final pathology tables, and a draft of this NTP Technical Report. Audit procedures and findings are presented in the reports and are on file at NIEHS. The audit findings were reviewed and assessed by NTP staff, and all comments were resolved or otherwise addressed during the preparation of this Technical Report.
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): gallium arsenide
- Physical state: solid, dark gray to black, fine powder
- Analytical purity: >98%, with total impurities <170ppm
- Lot/batch No.: M051988
- Stability under test conditions: gallium arsenide was found to be stable for 2 weeks at temperatures up to 60°C when stored protected from light. Stability was monitored by the study laboratory throughout the studies with chelometric titration. No degradation of the bulk chemical was detected.
- Storage condition of test material: the bulk chemical was stored in amber glass bottles with Teflon®-lined caps under a nitrogen headspace at room temperature.
- MMAD: 0.88 - 1.27 µm
- Origin: the analytical chemistry laboratory, Midwest Research Institute (Kansas City, MO) obtained gallium arsenide from Johnson Matthey, Inc. (Ward Hill, MA) and prepared the single lot.
No further details are given.

Test animals

Species:
mouse
Strain:
B6C3F1
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Simonsen Laboratories (Gilroy, CA)
- Age at study initiation: approx. 7 weeks old (4 weeks old on receipt)
- Weight at study initiation: range of means: 25.9 - 26.2 g (males); 20.6 - 20.9 g (females)
- Housing: individually; stainless steel wire bottom (Lab Products, Inc. Harford Systems Division, Aberdeen, MD), changed weekly
- Diet: ad libitum, except during exposure and urine collection periods; NIH-07 open formula pelleted diet (Zeigler Brothers, Inc., Gardners, PA), changed daily
- Water: ad libitum, softened tap water (Richland municipal supply) via automatic watering system (Edstrom Industries, Waterford, WI),changed weekly.
- Acclimation period: 20 days quarantine

ENVIRONMENTAL CONDITIONS
- Temperature (°C): ~23
- Humidity (%): 55 +/- 15
- Air changes: 15/hour
- Photoperiod: 12 hours dark/light cycle
No further details are given.

IN-LIFE DATES: From: 1989-03-07 To:1989-06-08/09

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
whole body
Vehicle:
air
Remarks on MMAD:
MMAD / GSD: range: 0.88 - 1.27 µm
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: the study laboratory designed the stainless-steel inhalation exposure chambers so that uniform vapour concentrations could be maintained throughout the chambers when catch pans were in place. The total active mixing volume of each chamber was 1.7 m³.
- System of generating particulates/aerosols: The gallium arsenide aerosol generation and delivery system had five basic components: a flexible-brush dust feed mechanism developed at the study laboratory, a Trost Model GEM-T air-impact mill, a cyclone separator, an aerosol charge neutraliser, and an aerosol distribution system. The flexible-brush dust feed mechanism employed a hopper into which the dry powder was poured. The hopper was reloaded with additional gallium arsenide at regular intervals throughout each day's exposure period. Aerosol passed through the charge neutraliser into the distribution line. At each chamber location, a vacuum pump drew aerosol from the distribution line into the chamber inlet, where the aerosol was further diluted with HEPA-filtered air to the appropriate concentration.
- Temperature, humidity in air chamber: 23-25°C, 55% +/- 15%
- Air change rate: 15 air changes per hour
- Method of particle size determination: The particle size distribution in each chamber was determined during pre-study testing and monthly during the 14-week study using a Mercer-style seven-stage impactor. The stages (glass coverslips lightly sprayed with silicone) were analysed by ICP/MS. The relative mass collected on each stage was analysed by probit analysis. The mass median aerodynamic particle diameter and the geometric standard deviation of each set of samples were estimated.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
- Chamber aerosol concentrations were monitored with real-time aerosol monitors (RAMs) that used a pulsed-light emitting diode in combination with a silicon detector to sense light scattered over a forward angular range of 45° to 95° by particles traversing the sensing volume. The instrument responds to particles 0.1 to 20 µm in diameter; the geometric diameter of gallium arsenide aerosol approached the minimum of this range. Each RAM was calibrated by correlating the measured voltage with gallium arsenide concentrations determined by analyzing exposure chamber samples collected on fiberglass filters. Filter samples were dissolved in nitric acid and analyzed for gallium arsenide using inductively coupled plasma/mass spectroscopy (ICP/MS). RAMs were calibrated one to two times weekly during the 16 day studies. Additional filter samples were collected every other day during the 16-day studies for gravimetric analysis of chamber concentrations as an additional check of monitor operation.
- Uniformity of aerosol concentration in the 16-day studies was evaluated prior to the start of the studies without animals present and once during each of the studies with animals present in the exposure chambers. Chamber concentration uniformity was acceptable throughout the studies
Duration of treatment / exposure:
16 days
Frequency of treatment:
6 hours/day, 5 days/week
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
1 mg/m3
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
10 mg/m3
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
37 mg/m3
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
75 mg/m3
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
150 mg/m3
Basis:
nominal conc.
No. of animals per sex per dose:
n=5 males, 4/5 females
Control animals:
yes
Details on study design:
- Dose selection rationale: 16-day range-finding study
- Rationale for animal assignment (if not random): animals were distributed randomly into groups of approximately equal initial mean body weights.
Positive control:
not applicable

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: weekly

BODY WEIGHT: Yes
- Time schedule for examinations: initially, on day 8, and at the end of the study

FOOD CONSUMPTION: No data

FOOD EFFICIENCY: No data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATIOn: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
- Necropsy was performed on all surviving study animals.
- Brain, heart, right kidney, liver, lung, right testis and thymus were weighed.

HISTOPATHOLOGY: Yes:
- Tissues for microscopic examination were fixed and preserved in 10% neutral buffered formalin, processed and trimmed, embedded in paraffin, sectioned to a thickness of 4 to 6 µm, and stained with hematoxylin and eosin.
- Complete histopathologic examinations were performed on all mice in the 0 and 150 mg/m3 groups and on target organs from all study mice to the no-observable-effect level.
Statistics:
Survival Analyses:
- The probability of survival was estimated by the product-limit procedure of Kaplan and Meier (1958).
- Statistical analyses for possible dose-related effects on survival used Cox.s (1972) method for testing two groups for equality and Tarone.s (1975) life table test to identify dose-related trends. All reported P values for the survival analyses are two sided.

Analysis of Neoplasm and Nonneoplastic Lesion Incidences:
- The Poly-k test (Bailer and Portier, 1988; Portier and Bailer, 1989; Piegorsch and Bailer, 1997) was used to assess neoplasm and nonneoplastic lesion prevalence.

Analysis of Continuous Variables:
- Organ and body weight data, which historically have approximately normal distributions, were analyzed with the parametric multiple comparison procedures of Dunnett (1955) and Williams (1971, 1972).
- Average severity values were analyzed for significance with the Mann-Whitney U test (Hollander and Wolfe, 1973).
- Treatment effects were investigated by applying a multivariate analysis of variance (Morrison, 1976) to the transformed data to test for simultaneous equality of measurements across exposure concentrations.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
All males and females in the 75 and 150 mg/m³ groups displayed hypoactivity and abnormal posture.
Mortality:
mortality observed, treatment-related
Description (incidence):
All males and females in the 75 and 150 mg/m³ groups displayed hypoactivity and abnormal posture.
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
lung weights of males and females exposed to 10 mg/m³ or greater were increased
Gross pathological findings:
not specified
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY
All males and females in the 75 and 150 mg/m³ groups displayed hypoactivity and abnormal posture.

BODY WEIGHT AND WEIGHT GAIN
- no effect

ORGAN WEIGHTS
- Lung weights of males and females exposed to 10 mg/m3 or greater were increased.

HISTOPATHOLOGY:
Compared to chamber controls, there were exposure-related microscopic lesions in the lung and larynx of exposed mice that were morphologically similar to those observed in the 16-day rat study.

Gallium arsenide particles were observed in alveolar macrophages of mice exposed to 150 mg/m³.
Alveolar proteinosis, epithelial hyperplasia, and histiocytic infiltrate occurred in all male and female mice exposed to 10 mg/m³ or greater.
Squamous metaplasia of the larynx also occurred in males and females exposed to 10 mg/m³ or greater, whereas chronic inflammation was observed in males and females exposed to 75 and 150 mg/m³.

Effect levels

open allclose all
Dose descriptor:
NOAEC
Remarks:
systemic
Effect level:
1 mg/m³ air (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: liver and thymus weights
Dose descriptor:
NOAEC
Remarks:
local
Effect level:
1 mg/m³ air (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: lung weights and histopathological changes in the lungs and larynx

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
Treatment of male and female mice by inhalation to concentrations of 0, 1, 10, 37, 75 and 150 mg/m3 gallium arsenide for 16 days revealed the following changes:
CLINICAL SIGNS AND MORTALITY
All males and females in the 75 and 150 mg/m³ groups displayed hypoactivity and abnormal posture.

ORGAN WEIGHTS
- Lung weights of males and females exposed to 10 mg/m3 or greater were increased.

HISTOPATHOLOGY:
Compared to chamber controls, there were exposure-related microscopic lesions in the lung and larynx of exposed mice that were morphologically similar to those observed in the 16-day rat study.

Gallium arsenide particles were observed in alveolar macrophages of mice exposed to 150 mg/m³.
Alveolar proteinosis, epithelial hyperplasia, and histiocytic infiltrate occurred in all male and female mice exposed to 10 mg/m³ or greater.
Squamous metaplasia of the larynx also occurred in males and females exposed to 10 mg/m³ or greater, whereas chronic inflammation was observed in males and females exposed to 75 and 150 mg/m³.
Executive summary:

Treatment of male and female mice by inhalation to concentrations of 0, 1, 10, 37, 75 and 150 mg/m3 gallium arsenide for 16 days revealed the following changes:

CLINICAL SIGNS AND MORTALITY

All males and females in the 75 and 150 mg/m³ groups displayed hypoactivity and abnormal posture.

ORGAN WEIGHTS

- Lung weights of males and females exposed to 10 mg/m3 or greater were increased.

HISTOPATHOLOGY:

Compared to chamber controls, there were exposure-related microscopic lesions in the lung and larynx of exposed mice that were morphologically similar to those observed in the 16-day rat study.

Gallium arsenide particles were observed in alveolar macrophages of mice exposed to 150 mg/m³.

Alveolar proteinosis, epithelial hyperplasia, and histiocytic infiltrate occurred in all male and female mice exposed to 10 mg/m³ or greater.

Squamous metaplasia of the larynx also occurred in males and females exposed to 10 mg/m³ or greater, whereas chronic inflammation was observed in males and females exposed to 75 and 150 mg/m³.