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EC number: 209-502-6 | CAS number: 583-39-1
Repeated dose toxicity: inhalation
Administrative data
- Endpoint:
- sub-chronic toxicity: inhalation
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Study period:
- 2012
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: see 'Remark'
- Remarks:
- A reliable secondary source, summarising 2-mercaptobenzimidazole properties, was used. However the primary sources were not revisited in order to verify their contents; for this reason reliability score 2 was used. The used secondary source has been updated on 2012; therefore it covers the most updated literature on the substance.
Data source
Reference
- Reference Type:
- secondary source
- Title:
- Prechronic inhalation toxicity studies of 2mercaptobenzimidazole (2MBI) in F344/N rats.
- Author:
- Gaworski CL, Aranyi C, Vana S, Rajendran N, Abdo K, Levine BS, Hall A 3rd.
- Year:
- 1 991
- Bibliographic source:
- PubMed - Fundam Appl Toxicol. 1991 Jan;16(1):161-71.
Materials and methods
Test guideline
- Qualifier:
- no guideline available
- Principles of method if other than guideline:
- It is not specified
- GLP compliance:
- not specified
Test material
- Reference substance name:
- Benzimidazole-2-thiol
- EC Number:
- 209-502-6
- EC Name:
- Benzimidazole-2-thiol
- Cas Number:
- 583-39-1
- Molecular formula:
- C7H6N2S
- IUPAC Name:
- 1H-benzimidazole-2-thiol
- Test material form:
- solid: particulate/powder
- Remarks:
- migrated information: powder
Constituent 1
Test animals
- Species:
- rat
- Strain:
- Fischer 344
- Sex:
- not specified
Administration / exposure
- Route of administration:
- inhalation
- Type of inhalation exposure:
- not specified
- Vehicle:
- not specified
Results and discussion
Results of examinations
- Details on results:
- Exposure-related histopathologic changes included pituitary cytoplasmic vacuolization, adrenal cortex necrosis, lymphoid depletion, thymic atrophy, liver cell hypertrophy, renal mineralization and tubular atrophy, and hypocellularity of the bone marrow.
Effect levels
open allclose all
- Dose descriptor:
- dose level:
- Effect level:
- >= 25 mg/m³ air
- Based on:
- test mat.
- Sex:
- not specified
- Basis for effect level:
- other: see 'Remark'
- Dose descriptor:
- dose level:
- Effect level:
- >= 6.2 mg/L air
- Based on:
- test mat.
- Sex:
- male/female
- Basis for effect level:
- other: Increased thyroid weight and thyroid follicular cell hyperplasia
- Dose descriptor:
- dose level:
- Effect level:
- ca. 3.1 mg/L air
- Based on:
- test mat.
- Sex:
- not specified
- Basis for effect level:
- other: Thyroid follicular cell hyperplasia was also seen in rats at 3.1 mg/m3
Target system / organ toxicity
- Critical effects observed:
- not specified
Any other information on results incl. tables
2-Mercaptobenzimidazole (2-MBI), used in rubber processing, is a suspect carcinogen structurally related to ethylene
thiourea. The inhalation toxicity of 2-MBI was evaluated in male and female F344/N rats exposed 6 hr/day, 5 days/week
to respirable aerosols generated by spray atomization of aqueous suspensions of the 2-MBI powder and subsequent
drying of the resulting aerosols. Twelve exposures at target concentrations of 0, 6.3, 12.5, 25.0, 50.0, or 100 mg/m3 of
2-MBI produced a dose-related reduction in body weight gains, thyroid follicular cell hyperplasia, adrenal cortex fatty
change, and pituitary atrophy. Sub-chronic exposures were conducted at target concentrations of 0, 3.1, 6.2, 12.5, 25.0,
and 50.0 mg/m3 of 2-MBI. Rats at greater than or equal to 25 mg/m3 displayed hunched posture, hypoactivity, and
reduced body weight gain, with compound related mortality at the highest exposure level. Anemia; increased SGPT,
SGOT, alkaline phosphatase, sorbitol dehydrogenase, BUN, and cholesterol; and reduced free fatty acid were seen in
rats at greater than or equal to 25 mg/m3. Increased thyroid weight and thyroid follicular cell hyperplasia were noted in
both sexes at greater than or equal to 6.2 mg/m3, with reduced triiodothyronine and thyroxine levels in both sexes at
greater than or equal to 12.5 mg/m3. Thyroid follicular cell hyperplasia was also seen in rats at 3.1 mg/m3. Thymus
weights were significantly reduced in both sexes at all exposure levels with liver weight increases at greater than or
equal to 6.2 mg/m3. Exposure-related histopathologic changes included pituitary cytoplasmic vacuolization, adrenal
cortex necrosis, lymphoid depletion, thymic atrophy, liver cell hypertrophy, renal mineralization and tubular atrophy, and
hypocellularity of the bone marrow.
Applicant's summary and conclusion
- Conclusions:
- According to Directive 67/548/EEC and to Regulation (EC) n. 1272/2008, the substance should be classified for specific target organ toxicity after repeated exposure.
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