Indium phosphide

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

A two-year study assessing the testicular damage induced following intratracheal instillations of Indium phosphide was conducted. Male Syrian golden hamsters were instilled with 3.0 mg/kg bw of Indium Phosphide twice a week for 8 weeks.

Animals were periodically sacrificed at 0, 8, 16, 40, 64 and 88 weeks after the last instillation.

Observed effects included those on the weight loss of animals and reproductive organs(testes and epididymis), decrease in sperm cell count and histopathological lesions in the seminiferous tubules.

From week 0 to 8 body weights and organ weights (epididymis and testes) of hamsters were comparable to those of chamber controls and changed significantly from week 16 to 64 where body weights diminished to 80-90% of control animals and organ weights to 60-70%. Both the body weights and organ weights returned to compatibility on week 88.

Similarly incidences of histopathologic changes in the seminiferous tubules were comparable to control values up till week 8 and changes occurred at week 16 to week 64.

The caudal sperm count in treated animals significantly decreased immediately after the last instillation and continued to decrease from week 16 to 64 where it was between 40-50%. Recovery of the caudal sperm count to the control level was seen at week 88 when serum indium concentrations were decreased by half.

Testicular damages were seen to recover in week 88 in line with the decrease in serum indium.

Considering the severity of the effects on reproductive organs and caudal sperm count compared to the generic toxic effects, they were not considered as non-specific, secondary effects. The authors concluded Indium Phosphide to be a testicular toxicant.

Link to relevant study records

Reference

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2000

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

- Principle of test: Effects of indium phosphide on male genital organs were observed in hamsters after intra-tracheal instillation of 3 mg/kg bw of Indium Phosphide twice a week for 8 weeks. Testicular damage was evaluated 0, 8, 16, 40, 64 and 88 weeks after instillation.
- Short description of test conditions: Male Syrian golden hamsters six weeks of age were housed in stainless steel cages at temperatures of 22-25°C, air humidity 50-60% and a light cycle of 12 hrs day and 12 hrs night. Food and water were provided ad libitum. Following a two week acclimation period hamsters 8 weeks of age were randomised by weight in to groups (controlled and exposed). Hamsters were intratracheally instilled with a 2.0 mL suspension/kg body weight under ether anaesthesia. A single instillation dose of the tests material was 3.0 mg/kg body weight. Hamsters in the control group were given phosphate buffer solution only. Hamsters were treated twice daily for 8 weeks.
- Parameters analysed / observed: Testes and epididymis were removed and weighted, sperm counter was performed using the right cauda epididymis, and histopathological changes in the right testis were investigated.

GLP compliance:

no

Limit test:

no

Species:

hamster, Syrian

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Japan SLC,Inc.
- Age at study initiation: 8 weeks
- Weight at study initiation: mean body weight of 111.6 g
- Housing: stainless steel cage
- Diet : CE-2 feed (ad libitum)
- Water: Tap water (ad libitum):
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22-25
- Humidity (%): 50-60
- Photoperiod (hrs dark / hrs light): 12 hrs dark / 12 hrs light

Route of administration:

intratracheal

Mass median aerodynamic diameter (MMAD):

1.06 µm

Geometric standard deviation (GSD):

1.8

Vehicle:

other: Pathogen free Phosphate bufer solution

Details on exposure:

VEHICLE
- Concentration in vehicle: 1.5 mg/mL

Details on mating procedure:

Not applicable

Analytical verification of doses or concentrations:

no

Details on analytical verification of doses or concentrations:

Not reported

Duration of treatment / exposure:

8 weeks

Frequency of treatment:

twice weekly

Details on study schedule:

Not applicable

Dose / conc.:

3 other: mg/kg bw, twice a week

Dose / conc.:

0 other: mg/kg bw, twice a week

No. of animals per sex per dose:

48 males / dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Rationale for animal assignment (if not random): randomised by weight

Positive control:

No

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Not reported

DETAILED CLINICAL OBSERVATIONS: Not reported

BODY WEIGHT: Yes
- Time schedule for examinations: 0, 8, 16, 40,64 and 88 weeks after the last instillation

Oestrous cyclicity (parental animals):

Not applicable

Sperm parameters (parental animals):

Parameters examined in [all/P/F1/F2] male parental generations: Testes and epididymis were removed and weighted, sperm counter was performed using the right cauda epididymis, and histopathological changes in the right testis were investigated.

Litter observations:

Not applicable

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals were sacrificed 0, 8,1 6, 40, 64 and 88 weeks after the last instillation.

HISTOPATHOLOGY / ORGAN WEIGHTS: Organ weights for reproductive organs such as the testis and epididymis were recorded. Histopathological analysis of testis were undertaken.

Postmortem examinations (offspring):

Not applicable

Statistics:

The F test was performed to evaluate the equality of variance.If a significant difference was found,a t test with Welch's correction was used for the statistical analysis otherwise a t test without a correction was used. Differences were considered significant at p<0.05

Reproductive indices:

Not reported

Offspring viability indices:

Not applicable

Clinical signs:

not specified

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, non-treatment-related

Description (incidence):

Three hamsters died of thinness, four were cannibalized (control group) and four were accidentally killed before examination (control group) during the observation period.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weights were comparable to chamber controls instantly succeeding instillation. However, they significantly diminished to 80-90% of chamber control from week 16 to week 64 prior to returning to compatibility with the control group at 88 weeks after the last instillation.

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not specified

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Serum indium concentration decreased by approximately half starting from the 8 week period and continuing to week 88 after the last instillation.

Clinical biochemistry findings:

not specified

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Immunological findings:

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

The incidences of seminiferous tubules with histopathologic changes were comparable to the control value up till week 8 following instillation. Vacuolization of seminiferous epithelium was frequently observed as an early histopathologic change.
Spermatogonia remained in the seminiferous tubules with severe histopathologic changes.
Significant changes occurred from week 16 to 64.
From weeks 16 to 88 after instillation, 30-50% of seminiferous tubules have histopathologic alterations, while abnormalities linked to age are observed in 14% of seminiferous tubules in controls at week 88. Histologic alterations included exfoliation and disarrangement of seminiferous epithelium, degeneration and loss of germ cells, and atrophy of seminiferous tubules without alteration of spermatogonia.

Histopathological findings: neoplastic:

no effects observed

Other effects:

not specified

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

effects observed, treatment-related

Description (incidence and severity):

The caudal sperm count in the Indium exposed group decreased significantly immediately after the last instillation before effects on bodyweights were observed, suggesting that it is not secondary to other toxic effects. The caudal sperm count decreased further from week 16 to 64 and was between 40-50% during this period post instillation. The caudal sperm count recovered to the control level 88 weeks after the last instillation.

Reproductive performance:

not specified

Key result

Dose descriptor:

LOAEL

Effect level:

3 other: mg/kg bw, twice weekly

Based on:

test mat.

Sex:

male

Basis for effect level:

body weight and weight gain

histopathology: non-neoplastic

reproductive function (sperm measures)

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

3 mg/kg bw/day (nominal)

System:

male reproductive system

Organ:

cauda epididymis

seminiferous tubules

testes

Treatment related:

yes

Dose response relationship:

not specified

Relevant for humans:

not specified

Clinical signs:

not examined

Dermal irritation (if dermal study):

not examined

Mortality:

not examined

Body weight and weight changes:

not examined

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

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

not examined

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

not examined

Clinical signs:

not examined

Dermal irritation (if dermal study):

not examined

Mortality / viability:

not examined

Body weight and weight changes:

not examined

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

Sexual maturation:

not examined

Anogenital distance (AGD):

not examined

Nipple retention in male pups:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

not examined

Histopathological findings:

not examined

Other effects:

not examined

Behaviour (functional findings):

not examined

Developmental immunotoxicity:

not examined

Clinical signs:

not examined

Dermal irritation (if dermal study):

not examined

Mortality / viability:

not examined

Body weight and weight changes:

not examined

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

Sexual maturation:

not examined

Anogenital distance (AGD):

not examined

Nipple retention in male pups:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

not examined

Histopathological findings:

not examined

Other effects:

not examined

Behaviour (functional findings):

not examined

Developmental immunotoxicity:

not examined

Key result

Reproductive effects observed:

yes

Lowest effective dose / conc.:

3 other: mg/kg bw, twice weekly

Treatment related:

yes

Relation to other toxic effects:

reproductive effects occurring together with other toxic effects, but not as a secondary non-specific consequence of other toxic effects

Dose response relationship:

not specified

Relevant for humans:

not specified

Conclusions:

Effects on male genital organs and caudal sperm count were observed following an exposure to Indium Phosphide, which were not considered as secondary to other adverse effects.

Executive summary:

A two-year study assessing the testicular damage induced following intratracheal instillations of Indium phosphide was conducted. Male Syrian golden hamsters were instilled with 3.0 mg/kg bw of Indium Phosphide twice a week for 8 weeks.

Animals were periodically sacrificed at 0, 8, 16, 40, 64 and 88 weeks after the last instillation.

Observed effects included those on the weight loss of animals and reproductive organs(testes and epididymis), decrease in sperm cell count and histopathological lesions in the seminiferous tubules.

From week 0 to 8 body weights and organ weights (epididymis and testes) of hamsters were comparable to those of chamber controls and changed significantly from week 16 to 64 where body weights diminished to 80-90% of control animals and organ weights to 60-70%. Both the body weights and organ weights returned to compatibility on week 88.

Similarly incidences of histopathologic changes in the seminiferous tubules were comparable to control values up till week 8 and changes occurred at week 16 to week 64.

The caudal sperm count in treated animals significantly decreased immediately after the last instillation and continued to decrease from week 16 to 64 where it was between 40-50%. Recovery of the caudal sperm count to the control level was seen at week 88 when serum indium concentrations were decreased by half.

Testicular damages were seen to recover in week 88 in line with the decrease in serum indium.

Considering the severity of the effects on reproductive organs and caudal sperm count compared to the generic toxic effects, they were not considered as non-specific, secondary effects. The authors concluded Indium Phosphide to be a testicular toxicant.

Additional information

A toxicity reproduction study was performed using intratracheal instillation for 8 weeks (two instillations per week) with an observation period of 88 weeks.

Based on the observations, it was concluded that treatment-related adverse effects occurred impacting on the fertility of animals without being secondary to generic toxic effects.

Justification for classification or non-classification

The study performed and reported by Omura et al. (2000) was used as basis by the ECHA Committee for Risk Assessment to set the Harmonised Classification of Indium Phosphide as Repr. 2; H361f: Suspected of damaging fertility.

Despite the interpretation of the study being limited by the single dose administrated and the lack of assessment of the fertility function, the observed adverse effects to caudal sperm count and male reproductive organs were considered as sufficient to conclude on the toxicity of the substance to fertility. In addition, while this study was performed using intratracheal instillation, testing performed via the inhalation route showed that indium can accumulate in testes following chronic exposure, thus supporting the classification as Repr. 2.