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Toxicological information

Toxicity to reproduction

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Administrative data

Endpoint:
fertility, other
Remarks:
based on test type (migrated information)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1989-03-06 to 1989-06-07
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 14-week study was conducted in compliance with FDA Good Laboratory Practice Regulations (21 CFR, Part 58). In addition, as records from the 14-week study were submitted to the NTP Archives, this study was auditied retrospectively.
Principles of method if other than guideline:
Groups of rats were exposed by inhalation to gallium arsenide particles at different concentrations, 6 hours per day, 5 days per week, for 14 weeks. At the end of the 14-week exposure period, samples were collected for sperm motility and vaginal cytology evaluations. The 14-week study was conducted in compliance with FDA Good Laboratory Practice Regulations (21 CFR, Part 58). In addition, as records from the 14-week 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, 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.
- 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: 0.81 - 1.60 µm in the 14-week studies
No further details are given.

Test animals

Species:
rat
Strain:
Fischer 344
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: 130-135 g (males); 105-111 g (females)
- Housing: housed 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: 19 to 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: 6 (males) or 7 (females) March 1989 To: 6 (males) or 7 (females) June 1989

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure (if applicable):
whole body
Vehicle:
air
Details on 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 monthly 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.
Details on mating procedure:
not applicable
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 14-week study. Additional filter samples were collected on days not dedicated to RAM calibration for gravimetric analysis of chamber concentrations as an additional check of monitor operation.
- Uniformity of aerosol concentration 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:
14 weeks
Frequency of treatment:
6 hours/day, 5 days/week
Details on study schedule:
not applicable
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
0.1 mg/m³
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
1.0 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.
No. of animals per sex per dose:
Core study: 10 males and 10 females per group
Control animals:
yes
Details on study design:
- Dose selection rationale: in the 16-day study, the severity of alveolar proteinosis increased with increasing exposure concentration and was considered the primary reason for the concomitant increased lung weights. The proteinosis and lung weights were markedly increased in the 75 and 150 mg/m³ groups and represented the upper exposure limits for the 14-week study. Because effects were similar between the 75 and 150 mg/m3 groups, 75 mg/m³ was selected as the high exposure concentration for the 14-week study. Because a no-effect level was not achieved for the lung and the effects observed at 37 mg/m³ were similar to but less severe than those in the 75 mg/m³ group, the three lower concentrations for the 14-week study were spaced by a factor of ten.
- Rationale for animal assignment (if not random): randomly into groups of approximately equal initial mean body weights.
Positive control:
Not applicable

Examinations

Parental animals: Observations and examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: clinical examination was weekly

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

FOOD CONSUMPTION AND COMPOUND INTAKE: No data

WATER CONSUMPTION AND COMPOUND INTAKE : No data
Estrous cyclicity (parental animals):
- Vaginal samples were collected for up to 12 consecutive days prior to the end of the studies from all female rats exposed to 0, 10, 37, and 75 mg/m³ for vaginal cytology evaluations.
- The following parameters were evaluated: estrous cycle lengths and relative frequency of estrous stages.
Sperm parameters (parental animals):
- At the end of the studies, sperm samples were collected from all male rats in the 0, 10, 37, and 75 mg/m³ groups for sperm motility evaluations.
- The following parameters were evaluated: spermatid heads per testis and per gram testis, spermatid counts, and epididymal spermatozoal motility and concentration.


Litter observations:
not applicable
Postmortem examinations (parental animals):
GROSS PATHOLOGY: Yes
- Necropsy was performed on all surviving core study animals.

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 rats in the 0 and 75 mg/m³ groups.
- The following tissues were examined: clitoral gland, preputial gland, prostate gland, testes with epididymides and seminal vesicles, ovary and uterus.
- In addition, testis with epididymis were examined in all remaining groups of rats.

ORGAN WEIGHTS:
- Absolute and relative weights of right testis were measured upon study termination from male animals of all groups (0.1 - 75 mg/m3).
- The left cauda, left epididymis, and left testis were weighed from animals of the 0, 10, 37 and 75 mg/m3 groups.
Postmortem examinations (offspring):
not applicable
Statistics:
Analysis of neoplasm and non-neoplastic 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).
- Spermatid, and epididymal spermatozoal data, were analyzed using the nonparametric multiple comparison methods of Shirley (1977) and Dunn (1964). Jonckheere.s test (Jonckheere, 1954) was used to assess the significance of the dose-related trends and to determine whether a trend-sensitive test (Williams. or Shirley.s test) was more appropriate for pairwise comparisons than a test that does not assume a monotonic dose-related trend (Dunnett.s or Dunn.s test).
- 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.
Reproductive indices:
not applicable
Offspring viability indices:
not applicable

Results and discussion

Results: P0 (first parental animals)

General toxicity (P0)

Clinical signs:
no effects observed
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related

Reproductive function / performance (P0)

Reproductive function: estrous cycle:
no effects observed
Reproductive function: sperm measures:
effects observed, treatment-related
Reproductive performance:
not examined

Details on results (P0)

CLINICAL SIGNS AND MORTALITY
- All rats survived until the end of the study.
- No clinical findings related to exposure to gallium arsenide were observed.

BODY WEIGHT AND WEIGHT GAIN
- Body weight of males was decreased only in the 75 mg/m3 group (-8% of controls).
- Body weight gains of males in the 37 and 75 mg/m3 groups were significantly less than those of the chamber controls.

ORGAN WEIGHTS
- The absolute testis weight of males exposed to 75 mg/m3 (-55% of controls) and the cauda epididymis (-26 and -38%) and epididymis (-10 and -29%) weights of males exposed to 37 or 75 mg/m3 were significantly (p<0.01) decreased.

HISTOPATHOLOFY
- Testicular atrophy (minimal to marked severity) and epididymal hypospermia (mild to marked severity) were observed in all males exposed to 37 and 75 mg/m3, but not at concentrations at and below 10 mg/m3.
- Atrophy consisted of decreased thickness of the germinal epithelium of seminiferous tubules due to variable loss of spermatogonia, spermatids and spermatozoa.
- Hypospermia consisted of decreased numbers of spermatozoa and the presence of cellular debris and large nucleated cells within the lumina of the epididymis.

REPRODUCTIVE TOXICITY PARAMETERS (also see organ weights)
Males:
- Total spermatid heads per testis and per gram testis and spermatid counts were significantly decreased in males exposed to 75 mg/m3
- Epididymal spermatozoa motility was significantly reduced in males exposed to 10 mg/m3 or greater with 89.08±1.16 % motility in controls, 81.83±1.03% at 10 mg/m3, 70.28±2.80% at 37 mg/m3 and 0.20±0.14% at 75 mg/m3.
- Epididymal spermatozoa concentration was significantly (p<0.01) decreased at 75 mg/m3 in comparison to control (75±8 vs. 551±25).

Females:
- No significant differences were noted in the estimated length of the estrous cycle.

Effect levels (P0)

open allclose all
Dose descriptor:
LOAEC
Remarks:
(testicular toxicity)
Effect level:
10 mg/m³ air (nominal)
Based on:
test mat.
Sex:
male
Basis for effect level:
other: see 'Remark'
Dose descriptor:
NOAEC
Remarks:
(testicular toxicity)
Effect level:
1 mg/m³ air (nominal)
Based on:
test mat.
Sex:
male
Basis for effect level:
other: estimated NOAEC: detailed sperm parameters only examined at and above 10 mg/m3; clear dose response established; no effects on testis weights or histopathological changes in male sexual organs at 10 mg/m3 or below

Overall reproductive toxicity

Reproductive effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
Treatment of male rats by inhalation with concentrations of 0, 0.1, 1, 10, 37 and 75 mg/m3 gallium arsenide for 14 weeks revealed effects on absolute testis weight of males exposed to 75 mg/m3 and cauda epididymis/epididymis weights at and above to 37 mg/m3. In addition, total spermatid heads/testis and spermatid counts were decreased at 75 mg/m3, while epididymal spermatozoa motility was reduced at and above 10 mg/m3. The concentration of epididymal spermatozoa was decreased at 75 mg/m3. However, absolute and relative weights of right testis were decreased only at 75 mg/m3, and exposure related increased incidences of testicular atrophy and epididymal hypospermia were observed only in groups exposed to 37 mg/m3 or greater, but not at lower concentrations.
Based on detailed sperm parameter analysis, the concentration of 10 mg/m3 represents a LOAEC for effects on male fertility. Although detailed examinations were not performed at lower concentration levels, the lack of effects on testicular weights and histopathology of male reproductive organs at concentration of 10 mg/m3 and below gives sufficient evidence for a NOAEC to be established at 1 mg/m3.
No significant differences were noted in the estimated length of the estrous cycle in female rats.
Executive summary:

Treatment of male rats by inhalation with concentrations of 0, 0.1, 1, 10, 37 and 75 mg/m3 gallium arsenide for 14 weeks revealed effects on absolute testis weight of males exposed to 75 mg/m3 and cauda epididymis/epididymis weights at and above to 37 mg/m3. In addition, total spermatid heads/testis and spermatid counts were decreased at 75 mg/m3, while epididymal spermatozoa motility was reduced at and above 10 mg/m3. The concentration of epididymal spermatozoa was decreased at 75 mg/m3. However, absolute and relative weights of right testis were decreased only at 75 mg/m3, and exposure related increased incidences of testicular atrophy and epididymal hypospermia were observed only in groups exposed to 37 mg/m3 or greater, but not at lower concentrations.

Based on detailed sperm parameter analysis, the concentration of 10 mg/m3 represents a LOAEC for effects on male fertility. Although detailed examinations were not performed at lower concentration levels, the lack of effects on testicular weights and histopathology of male reproductive organs at concentration of 10 mg/m3 and below gives sufficient evidence for a NOAEC to be established at 1 mg/m3.

No significant differences were noted in the estimated length of the estrous cycle in female rats.