Gallium arsenide

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Link to relevant study records

Reference

Reference 1

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).

Reason / purpose for cross-reference:

reference to same study

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 mice 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 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

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system 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

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 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.

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. 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:

no data

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:

10 males and 10 females per group

Control animals:

yes

Details on study design:

- Dose selection rationale: the effects on the lungs in males and females exposed to 150 mg/m³ in the 16 day study were considered sufficiently severe to preclude the use of this exposure concentration in a 14-week study. The severities of these lesions were not as great as those observed in rats in the 16-day study. Because rats and mice were housed in the same chambers in the 14-week studies, mouse exposure concentrations were based on rat exposure concentrations.
- Rationale for animal assignment (if not random): Animals were distributed randomly into groups of approximately equal initial mean body weights.

Positive control:

Not applicable

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

Oestrous cyclicity (parental animals):

- Vaginal samples were collected for up to 12 consecutive days prior to the end of the studies from all female mice 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 mice 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.
- Right testis were weighed in all groups.

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 epididymis and seminal vesicle and uterus.
- In addition, testis with epididymis were examined in the remaining groups of mice.

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 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).
- 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

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

Histopathological findings: non-neoplastic:

no effects observed

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

effects observed, treatment-related

Reproductive performance:

not examined

CLINICAL SIGNS AND MORTALITY
-One female exposed to 75 mg/m3 died before the end of the study.

BODY WEIGHT AND WEIGHT GAIN
- Final mean body weights (-10% of controls) and body weight gain of males in the 75 mg/m3 group were significantly less than the chamber control.

ORGAN WEIGHTS
- Absolute and relative weights of right testis were significantly (p<0.01) decreased at and above 37 mg/m3, but not in the dose groups below (
HISTOPATHOLOGY
- Exposure related increases in the incidences of testicular atrophy (minimal to moderate severity) and epididymal hypospermia (mild to marked severity) were observed in males exposed to 10 mg/m3 or greater.
- Lesions were similar to those observed in rats.

REPRODUCTIVE TOXICITY PARAMETERS
Males:
- The absolute weights of the left testis (-7%, -55% and -57% of controls) , cauda epididymis (- 18%, -17% and -16% of controls) and epididymis (-18%, -23% and - 31% of controls) were decreased in males exposed to 10, 37, or 75 mg/m3, respectively.
- Total spermatid heads per testis and per gram testis and spermatid counts were significantly decreased in males exposed to 37 and 75 mg/m3.
- Spermatozoa motility was significantly reduced in males exposed to 37 mg/m3 or greater with 87.14±1.99 % motility in controls, 82.48±1.66% at 10
mg/m3, 1.19±0.74% at 37 mg/m3 and 3.26±1.84% at 75 mg/m3.
- The concentration of epididymal spermatozoa were significantly decreased (p<0.01) in all groups exposed to 10 mg/m3 or higher (358±82, 18±3, 21±5, respectively) compared to control (1129±60).

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

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 1 mg/m3 or below

Remarks on result:

not measured/tested

Reproductive effects observed:

not specified

Conclusions:

Treatment of male mice by inhalation to concentrations of 0, 0.1, 1.0, 10, 37 and 75 mg/m3 gallium arsenide for 14 weeks revealed effects on absolute weights of left testis and cauda epididymis/epididymis at 10, 37, or 75 mg/m3. Total spermatid heads/testis, spermatid counts and spermatozoa motility were decreased at 37 and 75 mg/m3, while the concentration of epididymal spermatozoa was decreased in all groups exposed to 10 mg/m3 or higher. However, absolute and relative weights of right testis were decreased only at and above 37 mg/m3, and exposure related increases in the incidences of testicular atrophy and epididymal hypospermia were observed only in groups exposed to 10 mg/m3 or greater, but not at lower concentrations. Lesions were similar to those observed in rats.
Based on detailed sperm parameter analysis, the concentration of 10 mg/m3 represents a LOAEC for effects on male fertility. Although detailed examination were not performed at lower concentration levels, the lack of effects on testicular weights and histopathology of male reproductive organs at concentration of 1 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 mice.

Executive summary:

Treatment of male mice by inhalation to concentrations of 0, 0.1, 1.0, 10, 37 and 75 mg/m3 gallium arsenide for 14 weeks revealed effects on absolute weights of left testis and cauda epididymis/epididymis at 10, 37, or 75 mg/m3. Total spermatid heads/testis, spermatid counts and spermatozoa motility were decreased at 37 and 75 mg/m3, while the concentration of epididymal spermatozoa was decreased in all groups exposed to 10 mg/m3 or higher. However, absolute and relative weights of right testis were decreased only at and above 37 mg/m3, and exposure related increases in the incidences of testicular atrophy and epididymal hypospermia were observed only in groups exposed to 10 mg/m3 or greater, but not at lower concentrations. Lesions were similar to those observed in rats.

Based on detailed sperm parameter analysis, the concentration of 10 mg/m3 represents a LOAEC for effects on male fertility. Although detailed examination were not performed at lower concentration levels, the lack of effects on testicular weights and histopathology of male reproductive organs at concentration of 1 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 mice.

The dust of GaAs is classified as: Repr. 1B H360: May damage fertility

Reference 2

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).

Reason / purpose for cross-reference:

reference to same study

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

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system 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

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

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

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

Oestrous 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

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

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

effects observed, treatment-related

Reproductive performance:

not examined

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.

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

Remarks on result:

not measured/tested

Reproductive effects observed:

not specified

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.

The dust of GaAs is classified as: Repr. 1B H360: May damage fertility

Effect on fertility: via inhalation route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

1 mg/m³

Study duration:

subchronic

Species:

other: rats and mice

Additional information

Potential effects on male and female rats and mice fertility were evaluated in the context of 14 -week inhalation toxicity studies (NTP, 2000) by examination of male sperm parameters, histopathology of reproductive organs and vaginal cytology.

Basically, the overall hematological, histopathological and sperm findings reported by NTP (2000) were reproduced on male rats and mice in the context of 14 -week inhalation toxicity studies by Ma-Hock (2016).

Two further studies with intratracheal instillation of GaAs to male hamsters and male rats are not sufficiently reliable and therefore ignored.

In a study of Morrissey et al. 1987, developmental toxicity of intratracheally instilled GaAs was investigated in rats. No maternal effects and developmental effects up do a dose of 200 mg/kg GaAs have been observed. However, the study is available as meeting abstract only and reliability could not be evaluated. The study was considered as not assignable.

NTP (2000):

Exposure in the 2 reliable studies was whole-body 6h/d, 5d/week for 14 weeks to aerosols with median mass aerodynamic particle diameters (MMAD 0.8 - 1.0 µm). For the evaluation of potential effect on fertility male and female rats and mice were treated with concentrations of 0, 10, 37 and 75 mg/m³ gallium arsenide.

There was no effect of exposure on the estrous cycles of female rats or mice.

Rats:

Testicular atrophy and epididymal hypospermia were abserved in all males exposed to 37 or 75 mg/m³. Atrophy was generally of minimal severity in the 37 mg/m³ group and of moderate to marked severity in the 75 mg/m³ group. Atrophy consisted of decreased thickness of the germinal epithelium of seminiferous tubules due to variable loss of spermatogonia, spermatids, and spermatozoa. Sertoli cells lined severely affected tubules almost exclusively. Variable numbers of multinucleated syncytial cells were present in atrophic tubules. Epididymal hypospermia was generally of mild severity in the 37 mg/m³ group and of marked severity in the 75 mg/m³ group. Hypospermia consisted of decreased number of spermatozoa and the presence of cellular debris and large nucleated cells within the lumina of the epididymis.

Mice:

The right testis weight of males exposed to 37 or 75 mg/m³ were decreased, and the weights of the left testis, cauda epididymis, and epididymis were decreased in males exposed to 10 mg/m³ or higher. The total spermatid heads per testis and per gram testis, spermatid counts, and motility of epididymal spermatozoa were significantly decreased in males exposed to 37 and 75 mg/m³. The decreases in spermatozoa motilities of males exposed to 37 mg/m³ or greater were almost 100%. The concentrations of epididymal spermatozoa were decreased in all groups exposed to 10 mg/m³ or greater.

In summary:

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

Short description of key information:
Effects of gallium arsenide on male and female reproductive organs were examined in 14-week inhalation toxicity studies in rats and mice (NTP, 2000).

Basically, the overall hematological, histopathological and sperm findings reported by NTP (2000) were reproduced on male rats and mice in the context of 14 -week inhalation toxicity studies by Ma-Hock (2016).

2 further studies with intratracheal instillation of GaAs to hamsters and rats are not sufficiently reliable and therefore ignored.
Exposure in the reliable studies was whole-body 6h/d, 5d/week for 14 weeks to a GaAs dust with a median mass aerodynamic particle diameter (MMAD) 0.8 - 1.5 µm. Testicular effects were only seen at concentrations much higher than the lowest effect level.

In the 14-week study testicular effects occurred at 10 mg/m³ or higher concentrations with mice as well as with rats.

GaAs powder/dust and GaAs in its massive form and therefore also GaAs-wafers do not have to be classified and labelled with regard to reproduction toxicity according to the criteria of the CLP regulation (and of course according to Directive 67/548/EEC) and subsequent regulations.

Effects on developmental toxicity

Description of key information

The potential for gallium arsenide to cause developmental toxicity was assessed in Sprague-Dawley rats and CD-l (Swiss1) mice exposed to 0, 10, 37 or 75 mg/m³, 6 hours/day, 7 days/week. Rats were exposed on days 4 to 19 of gestation (gd) and mice on days 4 to 17 of gestation.
MICE: The two highest exposure concentrations were maternally lethal, and body weights and body weight gains were reduced in survivors. In mice, signs of pulmonary toxicity (dyspnoe and grey, mottled lungs) were seen at and above 37 mg/m³, and minimal pulmonary toxicity was already observed in mice of the 10 mg/m³ group, thus no NOAEC for maternal toxicity was established in mice. Developmental toxicity was evident in all three exposure groups in mice, and became statistically significant at and above 37 mg/m³.
RATS: Developmental toxicity in rats became obvious by increased incidences of concentration-related growth retardation, evidenced as reduced fetal body weight and an increased incidence of skeletal variations at and above 37 mg/m³. There was no evidence of embryotoxicity or frank teratogenicity. The NOAEC for developmental toxicity was 10 mg/m³. No mortality and effects on body weights were seen in rats. In rats signs of pulmonary toxicity (dyspnoe and grey, mottled lungs) were seen at and above 10 mg/m³.

Effect on developmental toxicity: via inhalation route

Dose descriptor:

NOAEC

10 mg/m³

Additional information

In a set of 2 fully reliable developmental toxicity studies, one with rats and one with mice, GaAs was tested for possible teratogenic effects (Mast et al., 1990). Exposure in these studies was whole-body 6h/d, 7d/week weeks to aerosols of 0, 10, 37 or 75 mg/m³ gallium arsenide. The overall average median mass aerodynamic particle diameter (MMAD) of the aerosol was 1.1 µm with a geometric standard deviation ranging beween 2.0 and 2.1.

MICE: The potential for gallium arsenide to cause developmental toxicity was assessed in CD-l (Swiss1) mice exposed on days 4 -17 of gestation (dg).

The two highest exposure concentrations were maternally lethal in mice, and body weights and body weight gains were reduced in survivors. Signs of pulmonary toxicity (dyspnoe and grey, mottled lungs) were seen at and above 37 mg/m³, and minimal pulmonary toxicity was observed in the 10 mg/m³ group, thus no NOAEC for maternal toxicity was established in mice. Developmental toxicity was evident in all three exposure groups in mice, and became statistically significant at and above 37 mg/m³.

RATS:

The potential for gallium arsenide to cause developmental toxicity was assessed in Sprague-Dawley rats exposed on days 4 -19 of gestation (dg).

No mortality and effects on body weights were seen in rats. Signs of pulmonary toxicity (dyspnoe and grey, mottled lungs) were seen at and above 37 mg/m³. Developmental toxicity in rats became obvious by increased incidences of concentration-related growth retardation, evidenced as reduced fetal body weight and an increased incidence of skeletal variations at and above 37 mg/m³. There was no evidence of embryotoxicity or frank teratogenicity. The NOAEC for developmental toxicity was 10 mg/m³.

Pregnant and virgin rats exhibited signs of pulmonary toxicity (dyspnoe and grey, mottled lungs), however, there were no effects on maternal body weight. The maternal NOAEL for inhaled gallium arsenide in rats was at least 10 mg/m³.

For both tests, developmental toxicity in the form of concentration-related growth retardation, evidenced as reduced fetal body weight and an increased incidence of skeletal variations became statistically significant at and above 37 mg/m³. There was no evidence of embryotoxicity or frank teratogenicity. The NOAEL for developmental toxicity was 10 mg/m³ if determined solely on the basis of adverse effects achieving statistical significance.

Reproduction toxicity effects were only seen at concentrations much higher than the lowest effect level. The lowest effect level in the 2-year rat study (NTP, 2000), 0.01 mg GaAs/m³, caused pulmonary alveolar proteinosis leading to pulmonary chronic active inflammation in a considerable number of rats. The lowest effect level in the 2-year mouse study, 0.1 mg GaAs/m³, caused an increased incidence of cellular infiltration in the lung.

In Mast et al. (1990), developmental effects only occurred at exposure concentrations where marked inflammation of the lungs with consecutive haematologic changes such as anemia were seen.

Justification for classification or non-classification

From the detailed evaluation of the available reliable data in comparison with the criteria set out in the CLP-regulation (see table below and section discussion) it is concluded that GaAs dust should be classified with regard to reprotoxicity in Cat 2 (Repr. 2, H361).

According to the harmonised classification and labelling approved by the European Union, this substance may damage fertility (Repr. 1, H360F).