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Toxicological information

Acute Toxicity: inhalation

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Administrative data

Endpoint:
acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study well documented, meets generally accepted scientific principles (similar to OECD test guideline 403), acceptable for assessment

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1981

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 403 (Acute Inhalation Toxicity)
GLP compliance:
not specified
Test type:
standard acute method
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female

Administration / exposure

Route of administration:
inhalation: gas
Type of inhalation exposure:
whole body
Vehicle:
other: unchanged (no vehicle)
Details on inhalation exposure:
Each dose group consisted of 5 male and 5 female rats, which were combined for a 4-h exposure or sham exposure to air in a customized 75-l glass chamber and then separated for observation over the subsequent 14-day period.  The rats were deprived of food and water during actual exposure or sham exposure. 
Analytical verification of test atmosphere concentrations:
not specified
Duration of exposure:
4 h
Concentrations:
400, 600, 650, 680, 690, 700 and 800 ppm
No. of animals per sex per dose:
5
Control animals:
yes
Details on study design:
Animals from any group that died during the 14-day period were examined for gross pathology, such as general or local haemorrhage and adhesions, and the survivors were sacrificed and examined as well.  Mortality and such visually apparent behaviour as exploring, huddling, preening, and obvious distress were noted during the course of the 4-hour exposure and sham exposure.
Statistics:
LC50 values and 95% confidence limits were estimated by the classical method of Litchfield and Wilcoxon (1949).

Results and discussion

Effect levels
Sex:
male/female
Dose descriptor:
LC50
Effect level:
675 ppm
95% CL:
643 - 709
Exp. duration:
4 h
Remarks on result:
other: exposure to a gas

Any other information on results incl. tables

The table summarizes the 14-d, 4-h LC50 determinations for
methyl mercaptan. In all cases, any animal that survived the
first 24 h after exposure survived to the end of the 2-wk
observational period. There was no evidence of external
bleeding from any orifice in rats that succumbed or
survived.

Dose-Response Summary for Acute Inhalation Exposures
----------------------------------------------------
Dose                        Mortality
(ppm)                         (male and female combined)                        
----------------------------------------------------
Sham                       0/10
400                        0/10
600                        2/10
650                        5/10
680                        4/10
690                        4/10
700                        10/10
800                        10/10
----------------------------------------------------

- LC50 = 675 (643-709) ppm
       = 1330 mg/m3 (1265 - 1400 mg/m3)

Applicant's summary and conclusion

Interpretation of results:
toxic
Remarks:
Migrated information Category 3 Criteria used for interpretation of results: other: REGULATION (EC) No 1272-2008
Executive summary:

Sprague-Dawley rats (5/sex/concentration) were exposed to a sham atmosphere or to methanethiol at 400, 600, 650, 680, 690, 700, or 800 ppm for four hours. Animals were observed for 14 days following the exposure. No mortality was observed in the sham exposure or at 400 ppm. Mortality increased with increasing concentrations of methanethiol with 2/10, 5/10, 4/10, 4/10 deaths at 600, 650, 680, and 690 ppm, respectively and complete mortality (10/10) at ≥ 700 ppm. Visually apparent behaviors during exposure to methanethiol or sham atmosphere included exploring, huddling, preening and distress, although there was no evidence of external bleeding. The 4-hr LC50for methanethiol in the rat was 675 ppm (1.33 mg/L).