Methanethiol

Acute Toxicity: inhalation

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

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

GLP compliance:

not specified

Test type:

standard acute method

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Methanethiol

EC Number:

200-822-1

EC Name:

Methanethiol

Cas Number:

74-93-1

Molecular formula:

CH4S

IUPAC Name:

methanethiol

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).