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Toxicological information

Repeated dose toxicity: inhalation

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Administrative data

Endpoint:
sub-chronic toxicity: inhalation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well-documented publication.
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
publication
Title:
Olfactory neuron loss in adult male CD rats following subchronic inhalation exposure to hydrogen sulfide.
Author:
Brenneman, K.A.; et al.
Year:
2000
Bibliographic source:
Toxicologic Pathology, 28: 326-333

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
The purpose of this study was to subchronically expose 10-week old male CD rats to relatively low concentrations of H2S and to histologically evaluate the nasal cavity for exposure-related lesions. Rats were exposed via inhalation to 0, 10, 30, or 80 ppm H2S for 10 weeks.
GLP compliance:
not specified
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Test material form:
other: gaseous
Details on test material:
- Name of test material (as cited in study report): Hydrogen sulfide
- Molecular formula (if other than submission substance): H2S
- Molecular weight (if other than submission substance): 34.08 g/mol
- Smiles notation (if other than submission substance): S
- InChl (if other than submission substance): InChl=1/H2S/h1H2
- Substance type: technical product
- Physical state: gaseous

Test animals

Species:
rat
Strain:
Crj: CD(SD)
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Raleigh, NC
- Age at study initiation: 10 weeks
- Housing: individually in polycarbonate cages (Nalge, Rochester, NY) with stainless steel wire lids and Alpha-Dri cage litte and without filter tops (except during the third and fourth weeks of exposure when they were housed overnight with a single female rat for a separate breeding study)
- Diet: NIH-07 pelleted rodent chow (Zeigler Brothers, Gardners, PA) ad libitum (except during exposures)
- Water: deionised filtered tap water ad libitum
- Rats were quarantined for a 2 weeks period

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 °C ±3 °C (average±SD)
- Humidity (%): 50 %±20 %
- Air changes (per hr): high-efficiency particulate air (HEPA)-filtered air
- Photoperiod (hrs dark / hrs light): 12/12

- Cages were cleaned approximately weekly

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure:
not specified
Vehicle:
air
Remarks on MMAD:
MMAD / GSD: not applicable
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Hydrogen sulfide exposure concentrations were generated by metering 5 % (50,000 ppm) H2S in nitrogen from a gas cylinder through a mass flow controler and diluting the gas with the chamber air supply.
- Total air flow through each 1m3 chamber was maintained at approximately 200-250 L/min to provide 10-15 air changes per hour during the exposure.
- Temperature and humidity were maintained at 17.8 - 26.1 °C and 30 - 70 %, respectively.
- The generation system was operated by an infinity building automation system.
- The rats were exposed in R-24 stainless steel wire cage units, suspended in 4 Hazelton H1000 stainless steel and glass inhalation exposure chambers.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Chamber exposure concentrations were measured with a calibrated gas chromatograph equipped with a flame photometric detector and a GS-Q column.
Duration of treatment / exposure:
10 weeks
Frequency of treatment:
6 h/d, 7 d/wk
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
10 ppm (≈14 mg/m3 at 25 °C)
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
30 ppm (≈42 mg/m3 at 25 °C)
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
80 ppm (≈111 mg/m3 at 25 °C)
Basis:
nominal conc.
No. of animals per sex per dose:
12 rats per group
Control animals:
yes
Details on study design:
- Rationale for animal assignment (if not random): assigned to weight-matched exposure groups
Positive control:
no data

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: No data

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No data

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 data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: No data

CLINICAL CHEMISTRY: No data

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data
Sacrifice and pathology:
Rats were euthanatized approx. 24 h after last exposure

GROSS PATHOLOGY: No data

HISTOPATHOLOGY: Yes :
-Histological evaluation of the nasal cavity was performed: noses were dissected free, trimmed of excess soft tissue, retrograde flushed and immersion fixed with 10 % neutral buffered formalin, and then decalcified in 20 % formic acid with an ion exchange resin (for detailed description of the preparation and tissue processing, see publication).
The severity of non-olfactory nasal lesions was graded and the severity of olfactory lesions was subjectively evaluated. Furthermore olfactory neuron loss and basal cell hyperplasia was graded.
Statistics:
Fisher's exact test with a Bonferroni correction for multiple comparisons between exposed groups and the control group was used to determine the significance of differences between the incidences of nasal lesions found in control versus exposed groups.

Results and discussion

Results of examinations

Clinical signs:
not specified
Mortality:
not specified
Body weight and weight changes:
not specified
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:
not specified
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
not specified
Gross pathological findings:
not specified
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
not specified
Details on results:
HISTOPATHOLOGY: NON-NEOPLASTIC
- Following exposure of rats to 30 and 80 ppm H2S, a significant increase in nasal lesion limited to the olfactory mucosa was observed.
- The lesions, which consisted of olfactory neuron loss and basal cell hyperplasia, were multifocal, bilaterally symmetrical, and had a characteristic rostracaudal distribution pattern.

OTHER FINDINGS
TEST ATMOSPHERES
- The grand means (±SD) for the analytical chamber concentrations were 10.0±0.6 ppm, 30.1±0.8 ppm, and 79.5±2.4 ppm.

Effect levels

open allclose all
Dose descriptor:
NOAEC
Remarks:
local effects
Effect level:
10 ppm
Based on:
test mat.
Remarks:
dihydrogen sulfide
Sex:
male
Basis for effect level:
other: Following exposure to 30 and 80 ppm hydrogen sulfide, a significant increase in nasal lesions limited to the olfactory mucosa was observed. 10 ppm H2S representing the NOAEC for ONL (local effects) following sub-chronic inhalation.
Dose descriptor:
NOAEC
Remarks:
local effects
Effect level:
ca. 14 mg/m³ air
Based on:
test mat.
Remarks:
dihydrogen sulfide
Sex:
male
Basis for effect level:
other: see 'Remark'

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
A concentration of 10 ppm H2S (ca. 14 mg/m3 air at 25 °C) represented the NOAEC for ONL (local effects) following sub-chronic inhalation. However, because of the gaseous state of hydrogen sulfide, when drawing conclusions with respect to local effects at the olfactory system and respiratory tract, which might be generated by exposure to dust of sodium sulfide, the toxicokinetic behaviour (e.g. total absorption) of H2S and Na2S should be taken into consideration.