Hexachlorodisilane

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1 May 1983 to 18 August 1983

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1983

Report date:

1984

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Hydrogen chloride

EC Number:

231-595-7

EC Name:

Hydrogen chloride

Cas Number:

7647-01-0

Molecular formula:

H Cl

IUPAC Name:

chloride

Test animals

Species:

other: rat and mouse

Strain:

other: Sprague-Dawley rats, Fischer-344 rats, and B6C3F1 mice

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: No data
- Age at study initiation: No data
- Weight at study initiation: No data
- Fasting period before study: No
- Housing: Individually housed in 8 cubic meter stainless steel and glass inhalation chambers.
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: One week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): Data could not be found in report supplied
- Humidity (%): Data could not be found in report supplied
- Air changes (per hr): Data could not be found in report supplied
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 20 September 1984 To: 20 December 1984

Administration / exposure

Route of administration:

inhalation: gas

Type of inhalation exposure:

whole body

Vehicle:

clean air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Animals were housed and exposed in 8 cubic meter stainless steel and glass inhalation chambers.
The test substance was first passed through a regulator and was maintained at a pressure of 50 psig. It was then passed through a flowmeter which measured the flow rate. The gas was then mixed with a supply of filtered, dry air, introduced at the top of the inhalation chamber and exhausted at the bottom. The negative pressure of each test chamber was maintained at 0.1 inches of water. The control chamber was maintained at a positive pressure of 0.02 inches of water.

TEST ATMOSPHERE
- Brief description of analytical method used: Analyses of chamber scrub samples were performed throughout the study by a method involving the titration of dissolved chlorides with a dilute solution of mercuric nitrate in the presence of a mixed diphenylcarbazone-bromophenol blue indicator. Each test chamber was sampled approximately once per hour. The control chamber was sampled once daily.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analyses of chamber scrub samples were performed throughout the study by a method involving the titration of dissolved chlorides with a dilute solution of mercuric nitrate in the presence of a mixed diphenylcarbazone-bromophenol blue indicator. Each test chamber was sampled approximately once per hour. The control chamber was sampled once daily.

Duration of treatment / exposure:

90 days

Frequency of treatment:

six hours, five days per week

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

10 ppm

Remarks:

target concentration

Doses / concentrations 2

Dose / conc.:

20 ppm

Remarks:

target concentration

Doses / concentrations 3

Dose / conc.:

50 ppm

Remarks:

target concentration

No. of animals per sex per dose:

31 males and 21 females of each species/strain

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: No data
- Rationale for selecting satellite groups: Interim sacrifice group of 15 males and 10 females sacrificed after the fourth exposure.

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least twice daily for mortality and clinical signs of toxicity.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Weekly

BODY WEIGHT: Yes
- Time schedule for examinations: All animals: just prior to the first exposure (day 1), then weekly, and a final fasted body weight measurement was obtained prior to the 90-day sacrifice.

FOOD CONSUMPTION:
- Just prior to the first exposure (day 1), then weekly for each animal.

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At 90 days.
- Anaesthetic used for blood collection: Yes (ether)
- Animals fasted: Yes, for approximately 12 hours.
- How many animals: 10 males and 10 females
- Parameters checked in table 1 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At 90 days.
- Animals fasted: Yes, for approximately 12 hours.
- How many animals: 10 males and 10 females
- Parameters checked in table 1 were examined.

URINALYSIS: Yes, in 10 males and 10 females.
- Time schedule for collection of urine: At 90 days.
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes, for approximately 12 hours.
- Parameters checked in table 1 were examined.

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

15 males and 10 females per group per strain/species were sacrificed the day following the fourth exposure for pathological examination. After 90 days of exposure 10 males and 10 females per group per strain/species (same animals as those for clinical pathology) were sacrificed for pathological examination.

At the day 5 interim sacrifice the nasal turbinates, trachea, lung and gross lesions were examined microscopically. Organs and tissues examined microscopically at 90 days are summarised in Table 2.

Statistics:

Parametric data such as body weight and food consumption were analysed using an analysis of variance (ANOVA). Statistically significant differences that were noted were further studied by either Tukey's (equal populations) or Scheffe's (unequal populations) Test of Multiple Comparison. Non-parametric data such as organ weight ratios were analysed using a Kruskal-Wallis ANOVA and a Test of Multiple Comparison. Discontinuous data such as appropriate incidences of histopathological findings were compared using CHI-SQUARE or Fischer's Exact Probability Test.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Local effects

Mortality:

mortality observed, treatment-related

Description (incidence):

Local effects

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

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

Description (incidence and severity):

Relating to local effects

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: One female high dose mouse was found dead on study day 12, and four low dose male mice were found dead on study day 92. In addition, one high dose female mouse was sacrificed in extremis on study day 20. One high dose female Sprague-Dawley rat was found dead on study day 4. However, the study authors noted that the deaths did not appear to be related to exposure to HCl. Clinical signs were consistent with the irritant/corrosive properties of HCl (appendage, tail or lip injury in the form of toe missing/swollen/open/gelatinous, scabbed/deformed/lesion, crusty nose, tissue mass, mouth injury, scabbed nose, crusty muzzle, red stained fur, nasal discharge, crusty eye, poor coat quality

BODY WEIGHT AND WEIGHT GAIN: 50 ppm HCl resulted in decreased body weights in all four strains after four exposures. Following 90 days of exposure B6C3F1 male and female mice and male Sprague-Dawley rats exposed to 50 ppm had biologically significant decreases in body weight.

FOOD CONSUMPTION: After four days of exposure there were statistically significant decreases in food consumption for high dose male Sprague-Dawley rats and male Fischer 344 rats. After 90 days high dose mice had the largest reduction in food consumption. The rats did not show a consistent reduction in food consumption that could be deemed expsoure-related.

HAEMATOLOGY: there were no treatment-related effects.

CLINICAL CHEMISTRY: there were no treatment-related effects.

URINALYSIS: there were no treatment-related effects.

ORGAN WEIGHTS: decrease liver weight in high dose male and female mice and Fischer 344 female rats. The authors noted that this might have been due to the overall reduced body weights.

GROSS PATHOLOGY

HISTOPATHOLOGY: Animals exposed to all concentrations of HCl had minimal to mild rhinitis, which occurred in the anterior portion of the nasal cavity and was dose and time related. Mice also developed varying degrees of cheilitis with accumulations of haemosiderin-laden macrophages involving the perioral tissues at 50 ppm. At all exposure concentrations mice developed oesinophilic globules in epithelial cells lining the nasal turbinates after 90 days of exposure.

Effect levels

1

Dose descriptor:

NOAEC

Effect level:

20 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Systemic NOAEC based on reduced body weights at 50 ppm.

2

Dose descriptor:

LOAEC

Effect level:

10 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Local LOAEC based on irritant/corrosive effects seen at all dose levels tested in mice.

Target system / organ toxicity

Critical effects observed:

no

Applicant's summary and conclusion

Conclusions:

In a well conducted 90-day gas inhalation study (reliability score 1) the systemic NOAEC for hydrogen chloride was 20 ppm (30 mg/m3) based on decreased body weight following exposure to 50 ppm (6 hours/day, 5 days/week) in rats and mice. The main adverse findings related to irritant/corrosive effects on the nasal turbinates in mice.