Hydrogen chloride

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 to 18 August 1983

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Ophthalmic examinations were not performed. Results for the animals injected with [3H]-thymidine are not included in the report.

Data source

Reference

Reference Type:

other company data

Title:

Unnamed

Year:

1984

Report date:

1984

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

no

Principles of method if other than guideline:

Method: Not stated, but in agreement with OECD 413.

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:

Cl H

IUPAC Name:

hydrogen chloride

Details on test material:

Test substance: Hydrochloric acid gas
Lot/Batch number: Not stated
Description: Colourless gas
Purity: >99.99%
No further details specified.

Test animals

Species:

other: rat

Strain:

other: Rat - Sprague-Dawley (CD); Rat - Fisher-344 (CDF)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding laboratories, Inc., Portage, MI, USA
- Age at study initiation: 6-8 weeks old;
- Weight at study initiation: not specified.
- Fasting period before study: not specified.
- Housing:not specified.
- Diet (e.g. ad libitum): not specified.
- Water (e.g. ad libitum):not specified.
- Acclimation period:not specified.


ENVIRONMENTAL CONDITIONS
- Temperature (°C): not specified.
- Humidity (%):
During the study it was noted that target concentrations (i.e. 10 (Group T-I), 20 (Group T-II) and 50 (Group T-III) ppm) were achieved only at very high nominal values when chamber humidity was high (>40% relative humidity, temperature range 38-43 °C). Because of this, chamber humidity was kept at <40% relative humidity whenever possible. Apparently, the water content of air at relative humidity >40% is sufficient to greatly enhance the loss – through dissolution – of gaseous HCl onto the metal surfaces of the chamber.
- Air changes (per hr): not specified
- Photoperiod (hrs dark / hrs light): not specified.


IN-LIFE DATES: not specified.

Administration / exposure

Route of administration:

inhalation

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: not specified.

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
The test substance, contained in a gas cylinder, was first passed through a regulator then maintained at a pressure of 50 psig. It then passed through a flowmeter (located at each exposure chamber) which measured the flow rate. The gas was then mixed with a supply of filtered dry air introduced at the top centre of the inhalation chamber and exhausted at the bottom. The flow of test substance from the flowmeter and total air through the chamber were adjusted to maintain the target concentration within the chamber. The test substance delivery rate and total airflow were used in calculating the nominal concentration within the chamber.
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 once daily. The titration method was also used to analyze samples taken for measurement of build-up and decay rates and for distribution studies.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Time Weighed Average measured concentrations (ppm)
Group CD rats Fisher-344 rats
(males + females) (males + females)
T-I 10.15 9.8 9.35 9.8
T-II 17.6 19.0 18.7 19.1
T-III 45.05 46.7 48.85 46.8

Duration of treatment / exposure:

Either 4 days or 13 weeks

Frequency of treatment:

Daily, 6 hours a day, 5 days per week

Doses / concentrations

Remarks:

Doses / Concentrations:
10 (Group T-I), 20 (Group T-II) and 50 (Group T-III) ppm
Basis:
nominal conc.

No. of animals per sex per dose:

31 males and 21 females/species/strain/group. The groups were designated T-I, T-II, T-III
(10 animals/sex/species/strain/group either for interim sacrifice at the day following the fourth exposure or terminal sacrifice at 90 days; plus 5 males/species/strain/group injected intraperitoneally with [3H]-thymidine at a dose of 2 μCi/g bw approx. 2 hrs before both interim and terminal sacrifice (approx. 16 hr after exposure termination); plus 1male and 1 female/species/strain/group for viral serological examination at the final sacrifice.

Control animals:

other: clear air only

Details on study design:

Post-exposure period: None

Positive control:

No specified.

Examinations

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

MORTALITY: Yes
- Time schedule: At least twice daily

BODY WEIGHT: Yes
- Time schedule for examinations: Measured and recorded prior to the first exposure (day 1) and weekly thereafter. Final individual fasted bodyweight was recorded just prior to the 90 day sacrifice.

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- Time schedule: Weekly

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
Haematological examinations were carried out on 10 animals/sex/species/strain/group at terminal sacrifice. Samples were obtained via orbital sinus puncture from fasted animals under ether anaesthesia, using EDTA as anti-coagulant. The following parameters were examined: erythrocyte count, haemoglobin, haematocrit, total and differential leukocyte count, platelet and thrombocyte counts, mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), and mean corpuscular haemoglobin concentration (MCHC).


CLINICAL CHEMISTRY: Yes
Serum chemistry samples were obtained via the abdominal aorta from fasted animals (the same as above) under ether anaesthesia. The following parameters were measured: glutamic pyruvic transaminase, urea nitrogen, total bilirubin, glucose, inorganic phosphorus, calcium, and alkaline phosphatase.


URINALYSIS: Yes
Following 13 weeks of treatment, animals were individually placed in metabolic cages and fasted for approx. 12 hrs. The following parameters were evaluated: volume, appearance, occult blood, specific gravity, protein, pH, ketone and glucose.


NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table)
HISTOPATHOLOGY: Yes (see table)
ORGAN WEIGHT: Yes

10 animals/sex/species/strain/group were sacrificed the day following the fourth exposure for pathologic study.
Following 13 weeks treatment, the same animals used for clinical pathology were sacrificed and subjected to a full detailed necropsy.

After necropsy, the following organs were collected: brain, heart, kidney, liver, and ovaries/testes, trimmed to remove fat and other contiguous tissues and weighed.

For the interim sacrifice the following tissues were collected and examined microscopically: nasal turbinates (fixed by perfusion via the nasopharyngeal opening with approx. 5 mL of formaldehyde to remove air), trachea, lungs (distended with formalin) including sections of mainstem bronchi, secondary bronchioles, respiratory bronchioles – alveolar ducts, alveoli, and any gross lesion(s).
At terminal sacrifice tissue samples of the following organs were fixed in 10% buffered formalin, embedded in paraffin, sectioned, stained with haematoxylin and eosin, and examined by light microscope: nasal turbinates (fixed by perfusion via the nasopharyngeal opening with approx. 5 mL of formaldehyde to remove air), trachea, lungs (distended with formalin) including sections of mainstem bronchi, secondary bronchioles, respiratory bronchioles – alveolar ducts, alveoli, brain, heart, kidney, liver, testes, adrenal, duodenum, eyes and optic nerve, mesenteric lymph nodes, aorta, bone (sternum), ear canal, bone marrow, colon, epididymis, jejunum, mandibular lymph nodes, oviducts, ovaries, prostate, skin, pituitary gland, spinal cord, sciatic nerve, peripheral nerve, salivary gland, spleen, thyroid glands, urinary bladder, uterus, thymus, fore and glandular stomach, pancreas, parathyroid, skeletal muscle, seminal vesicle, tongue, bone (femur), caecum, oesophagus, ileum, lacrimal gland, mammary glands, larynx, and any gross lesion(s). Histopathology was performed on all tissues from all animals in control and high-dose groups; the nasal turbinates, trachea, lungs and any gross lesion(s) from animals in the T-I and T-II groups were also examined microscopically.

Other examinations:

At both interim and terminal sacrifices, 5 males/species/strain/group were injected intraperitoneally with [3H]-thymidine at a dose of 2 μCi/g bw approx. 2 hrs before sacrifice (approx. 16 hr after exposure termination), were sacrificed and their head removed and the cranial bones exposed. The brain, skin, eyes, lower jaw, tongue and any excess muscle and connective tissues were removed for histologic preparation of nasal passages. The nasal turbinates were then rinsed with Helly’s fixative through the nasopharynx and immersed in Helly’s fixative for 24 hrs. Following fixation, the head was rinsed in running tap water for 24 hrs, placed in 70% ethanol and shipped to the sponsor.

Statistics:

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

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

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:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

effects observed, treatment-related

Details on results:

CLINICAL SIGNS AND MORTALITY
Signs consistent with the irritant/corrosive properties of HCl were observed. They included crusty nose, red or yellow/brown stained fur, poor quality coat, crusty eye(s) and nasal discharge in rats.

One T-III female Sprague-Dawley (CD) rat (scheduled for interim sacrifice) was found dead on study day 4.
None of these deaths appeared to be directly related to exposure to gaseous HCl.
No Fisher-344 (CDF) rats died during the 90 day study.


BODY WEIGHT AND WEIGHT GAIN
At the time of interim sacrifice (after 4 exposures) body weight decreases compared to corresponding controls were statistically evident in high dose animals of both sex and species.
In the 90 day study, statistically significant decreases from corresponding controls in body weight were noted in
T-III Fisher-344 male rats showed statistically significant decreased body weights at weeks 2, 3, 5, 6 and 7.
Statistical analysis showed significant differences also for T-I Fisher-344 males (week 12) and T-III Fisher-344 female rats (total change). The decrease in body weight in T-I Fisher-344 male rats was apparently due to a loose water hose connection to their housing cage the evening before body weights were collected and actually, reanalysis of body weight data excluding the 5 affected rats revealed no statistically significant difference.
This difference, as well as the lone statistically significant difference recorded in T-III Fisher-344 female rats were not considered biologically significant.


FOOD CONSUMPTION
Data on food consumption up to interim sacrifice (13 to 15 males and 9 to 10 females/group) revealed statistically significant decreases for T-III male CD-rats and Fisher-344 male rats.
Statistically significant decreases from corresponding controls in food consumption were less frequent for Fisher-344 male T-III and T-II rats and least frequent in male T-III and female T-I CD rats during the 90 day study.

HAEMATOLOGY
Haematological analysis revealed no effects which were considered to be related directly to gaseous HCl.
Increased lymphocyte count was noted in female CD T-III rats only.


CLINICAL CHEMISTRY
Clinical chemistry was not affected.

URINALYSIS
Urinalysis was not affected.

ORGAN WEIGHTS
At the interim sacrifice, female T-III Fisher-344 rats showed decreased absolute liver weight. The decrease in the liver weights appears to parallel the body weight data for these animals and should be considered significant.
At the final sacrifice statistical analysis revealed increased absolute and relative heart weight in T-II female CD rats; increased relative heart weight in T-II and T-III male Fisher-344 rats, increased relative testes weight in T-III male Fisher-344 rats, and increased relative kidney weight in T-II female Fisher-344 rats: these findings were considered to be mainly related to the effect of treatment on general growth of affected animals rather than direct effect on the organs themselves.


GROSS PATHOLOGY AND HISTOPATHOLOGY
There was no notable gross pathology finding in animals found dead or sacrificed in extremis.

No specific gross pathological findings were noted at either the interim or terminal sacrifices.
Interim sacrifice


Histopathological examination of interim sacrifice CD rats revealed acute rhinitis in 3 male and 1 female T-II rats, and 5 male and 4 female T-III rats. Pneumocyte hyperplasia in single males at T-II and T-III and 2 females at T-II, and congestion of lung in a single T-III female were also noted.
Histopathological examination of interim sacrifice Fisher-344 rats also revealed acute rhinitis in a single T-II male, 4 T-III male and 4 T-III female rats. Besides, hyperkeratosis of nasal turbinates in 2 male and 2 female rats of both T-II and T-III groups, subacute rhinitis in 3 T-II male, 2 T-III male, 2 T-II female and 3 T-III female rats were also noted. A single case of focal subacute alveolitis was also detected in a T-III female.

Terminal sacrifice
In both CD and Fisher-344 rats, minimal to mild subacute (CD rats) and acute (Fisher-344 rats) rhinitis was noted at histopathology of most T-III or T-II animals of both sexes. The lesion occurred in the anterior proportion of the nasal cavity and was dose and time related.

There were no other treatment related histopathological findings.

Effect levels

1

Dose descriptor:

NOAEL

Effect level:

20 ppm

Sex:

male/female

Basis for effect level:

other: Mortality, clinical signs, food consumption, body weights and organ weights.

2

Dose descriptor:

LOAEL

Effect level:

50 ppm

Sex:

male/female

Basis for effect level:

other: Mortality, clinical signs, food consumption, body weights and organ weights.

3

Dose descriptor:

other: NOEL (rats)

Effect level:

10 ppm

Sex:

male/female

Basis for effect level:

other: Mortality, clinical signs, food consumption, body weights and organ weights.

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Tables with results are attached.

Sprague-Dawley (CD) rat, scheduled for interim sacrifice on study day 4).

Observations consisted mainly of signs related to the irritant/corrosive properties of HCl including crusty nose, red or yellow/brown stained fur, poor quality coat, crusty eye(s) and nasal discharge in rats.

At the time of interim sacrifice (after 4 exposures) body weight decreases compared to corresponding controls were statistically evident in high dose animals of both sexes.

Statistically and biologically significant decreases in body weight occurred at terminal sacrifice following 90 day exposure in male T-III Fisher-344 rats.

Food consumption was also affected in high dose animals, especially in rats of both strains at the interim sacrifice.

Analysis of haematology, serum chemistry and urinalysis parameters revealed no biologically significant differences from controls and no particular finding was noted at necropsy for both interim and terminal animals.

Decreases in liver weights were recorded at the interim sacrifice in high dose mice of both sexes and in high dose Fisher-344 female rats. At terminal sacrifice, similar findings were noted in male mice, together with increases in absolute or relative weight of some organs (heart weight in T-II female CD rats and T-II and T-III male Fisher rats, testes weight in high dose Fisher-344 rats, kidney weight in T-II female Fisher-344 rats). These variations were considered to be mainly related to the effect of treatment on the general growth of affected animals rather than direct effects on the organs themselves.

Histopathological examination did not reveal abnormalities while acute rhinitis was detected in a number of rats of both strains, especially at the highest dose level, at the interim sacrifice.

In both CD and Fisher-344 rats, minimal to mild subacute (CD rats) and acute (Fisher-344 rats) rhinitis was noted at histopathology of most T-III or T-II animals of both sexes. The lesions occurred in the anterior proportion of the nasal cavity and were dose and time related.

There were no other treatment related histopathological findings in any other organ or tissues.

Applicant's summary and conclusion

Conclusions:

Daily exposure of rats to gaseous hydrogen chloride at concentrations of 10, 20 and 50 ppm, 6 hours a day, 5 days per week up to a 90 day exposure period affected the body weight of males of one of the strains of rats at the highest dose level. Clinical signs observed were mainly related to the irritant/corrosive properties of HCl crusty nose, red or yellow/brown stained fur, poor quality coat, crusty eye(s) and nasal discharge in rats. No exposure-related changes were seen in haematology or clinical chemistry parameters or urinalysis, and no peculiar gross observations were noted at necropsy. Decreased liver weights and increases in other organs were recorded, but these changes were considered to be mainly related to the effect of treatment on general growth of the affected animals rather than direct effects on the organs themselves.
Histopathological examination after 90 days exposure revealed minimal to mild rhinitis in both strains of rats.

Based on effects on body weight both strains of rats, the LOAEL is considered to be 50 ppm in rats.
Based on the lack of effects on body weight and the lack of pathological findings except for effects of site-of-contact local irritation, the NOAEL for repeated dose inhalation toxicity can be set at 20 ppm for rats. The NOEL, at least for rats, can be set at 10 ppm.

Executive summary:

Some animals were found dead ( one T-III female Sprague-Dawley (CD) rat, scheduled for interim sacrifice on study day 4). The death appeared to be directly related to exposure to gaseous HCl.

Observations consisted mainly of signs related to the irritant/corrosive properties of HCl including crusty nose, red or yellow/brown stained fur, poor quality coat, crusty eye(s) and nasal discharge in rats.

At the time of interim sacrifice (after 4 exposures) body weight decreases compared to corresponding controls were statistically evident in high dose animals of both sexes.

Statistically and biologically significant decreases in body weight occurred at terminal sacrifice following 90 day exposure in male T-III Fisher-344 rats.

Food consumption was also affected in high dose rats of both strains at the interim sacrifice.

Analysis of haematology, serum chemistry and urinalysis parameters revealed no biologically significant differences from controls and no particular finding was noted at necropsy for both interim and terminal animals.

Decreases in liver weights were recorded at the interim sacrifice in high dose mice of both sexes and in high dose Fisher-344 female rats. At terminal sacrifice, heart weight in T-II female CD rats and T-II and T-III male Fisher rats, testes weight in high dose Fisher-344 rats, kidney weight in T-II female Fisher-344 rats). These variations were considered to be mainly related to the effect of treatment on the general growth of affected animals rather than direct effects on the organs themselves.

Histopathological examination did not reveal abnormalities in mice while acute rhinitis was detected in a number of rats of both strains, especially at the highest dose level, at the interim sacrifice.

In both CD and Fisher-344 rats, minimal to mild subacute (CD rats) and acute (Fisher-344 rats) rhinitis was noted at histopathology of most T-III or T-II animals of both sexes. The lesions occurred in the anterior proportion of the nasal cavity and were dose and time related.

There were no other treatment related histopathological findings in any other organ or tissues.