Agent Name

Methyl mercaptan

Alternative Name

Methanethiol

CAS Number

74-93-1

Formula

C-H4-S

Major Category

Toxic Gases & Vapors

Synonyms

Mercaptomethane; Methyl sulfhydrate; Methanethiol; Thiomethanol; Thiomethyl alcohol; [ChemID] UN1064

Category

Other Toxic Gases & Vapors

Description

Colorless gas with a disagreeable odor like garlic or rotten cabbage; Note: A liquid below 43 degrees F. Shipped as a liquefied compressed gas; [NIOSH]

Sources/Uses

Used as an odorant for some gases which are hazardous and odorless; used in the production of pesticides, jet fuel, plastics, and other organic chemicals; methyl mercaptan is a byproduct of the Kraft or sulfate process in paper and pulp production; [ACGIH] Produced from decaying organic matter and by pulp mills and oil refineries; [CAMEO]

Comments

A pulmonary irritant that can cause pulmonary edema after inhalation of high concentrations; Liver injury has been documented after occupational exposure. In high concentrations methyl mercaptan can cause coma and death, acting as a chemical asphyxiant similar to hydrogen sulfide. [ACGIH] Methemoglobinemia has been reported after occupational exposure. [HSDB] Possible frostbite from contact with liquid; [NIOSH]

Reference Link

ATSDR Medical Management - Methyl Mercaptan

Exposure Assessment
Skin Designation (ACGIH)

Insufficient data

TIH

Yes

TLV (ACGIH)

0.5 ppm

PEL (OSHA)

Ceiling(OSHA) = 10 ppm

MAK

0.5 ppm

IDLH (NIOSH)

150 ppm

Excerpts from Documentation for IDLHs

Human data: Students accidentally exposed to about 4 ppm for several hours experienced headaches and nausea [Clayton and Clayton 1981]. Some investigators have reported that the toxicity of methyl mercaptan is similar to hydrogen sulfide while others report the toxicity to be somewhat less than hydrogen sulfide [DeRekowski 1893; Frankel 1921].

Odor Threshold Low

2.0E-7 ppm

Odor Threshold High

0.04 ppm

Lethal Concentration

LC50 (rat) = 675 ppm

Explanatory Notes

Detection odor threshold from AIHA (mean = 0.00054 ppm); Flash point = -18 deg C;

Half Life

No reports found; [TDR, p. 893]

Reference Link

ICSC: Methyl mercaptan

Flammability (NFPA)

4: Burns readily

Adverse Effects
Toxic Pneumonitis

Yes

Hepatotoxin

Hepatotoxin, Secondary

Methemoglobinemia

Methemoglobinemia, Secondary

Other Poison

Chemical Asphyxiant

Links to Other NLM Databases
Health Studies

Human Health Effects from Hazardous Substances Data Bank:

Toxicity Information

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Chemical Information

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Biomedical References

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Related Information in HazMap
Diseases

Occupational diseases associated with exposure to this agent:

Processes

Industrial Processes with risk of exposure: