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Chemical Sampling Information (CSI)
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General Description

Synonyms: Chloromethane; Monochloromethane

OSHA IMIS Code Number: 1710

Chemical Abstracts Service (CAS) Registry Number: 74-87-3

NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) Identification Number: PA6300000

Department of Transportation Regulation Number (49 CFR 172.101) and Guide: 1063 115

NIOSH Pocket Guide to Chemical Hazards, Methyl chloride: chemical description, physical properties, potentially hazardous incompatibilities, and more

Exposure Limits

OSHA Permissible Exposure Limit (PEL):

General Industry: 29 CFR 1910.1000 Z-1 Table -- 100 ppm TWA; 200 ppm Ceiling for 5 mins. in any 3 hours; 300 ppm Peak

Maritime: 29 CFR 1915.1000 Table Z-Shipyards -- 100 ppm, 210 mg/m3 TWA

American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV): 50 ppm, 103 mg/m3 TWA; 100 ppm, 207 mg/m3 STEL; Skin; Appendix A4 - Not Classifiable as a Human Carcinogen

National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL): Appendix A - NIOSH Potential Occupational Carcinogens

Health Factors

Carcinogenic Classification:

International Agency for Research on Cancer (IARC): Group 3, not classifiable as to its carcinogenicity to humans

NIOSH Immediately Dangerous To Life or Health Concentration (IDLH): 2,000 ppm

Potential Symptoms: Dizziness; loss of appetite, nausea, vomiting; blurred or double vision, drooping eyelids, eye twitch; tremors of hands and lips, staggering, slurred speech, "drunken" behavior; headache, memory loss, confusion, hallucinations; convulsions; coma; burning sensation in mouth and throat, mustard-like taste, difficulty swallowing; cold clammy skin, rapid breathing, pulmonary edema; liver, kidney damage; frostbite, corneal burns (from liquid); [potential occupational carcinogen]

Health Effects: Acute CNS effects (HE4); Chronic CNS effects (HE7); Cumulative liver and kidney damage (HE3)

Affected Organs: CNS, liver, kidneys, skin, reproductive system


  1. Studies in rodents indicate that inhalation of methyl chloride can cause fetal growth retardation, impaired fertility in male rats and mouse fetal heart malformations.
  2. Toxicity may involve metabolism, in part, to formaldehyde by cytochrome P450 2E1, a liver enzyme inducible by chronic ethanol consumption, and to conjugates of glutathione in red blood cells by glutathione S-transferase theta, an enzyme missing in 10% to 64% of certain ethnic populations.

Literature Basis:

  • NIOSH Pocket Guide to Chemical Hazards: Methyl chloride.
  • International Chemical Safety Cards (WHO/IPCS/ILO): Methyl Chloride.
  • EPA Air Toxics Website: Methyl Chloride (Chloromethane). U.S. Environmental Protection Agency Technology Transfer Network.
  • Nelson, H.H., et al., Ethnic differences in the prevalence of the homozygous deleted genotype of glutathione S-transferase theta. Carcinogenesis 16(5): 143-1245, 1995.
  • No authors: Methyl chloride. IARC Monogr. Eval. Carcinog. Risks Hum. 71(Pt. 2): 737-747, 1999.
  • Pohanish, R.P. (editor): Methyl Chloride. In, Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens, Fourth Ed., Vol. 2. Norwich, NY: Noyes Publications, William Andrew Publishing, 2002, pp. 1537-1540.

Date Last Revised: 01/08/2004

Monitoring Methods used by OSHA

Primary Laboratory Sampling/Analytical Method (SLC1):

  • sampling media: Two charcoal tubes in series (First tube 400/200 mg sections, second tube 100/50 mg sections, both 20/40 mesh)
    analytical solvent: Methylene Chloride
    maximum volume: 3.0 Liters
    maximum flow rate: 0.1 L/min (TWA)
    maximum volume: 1.5 Liters
    maximum flow rate: 0.1 L/min (STEL)
    minimum time: 5 Minutes   
    maximum flow rate: 0.1 L/min (Ceiling)
    minimum time: 5 Minutes   
    maximum flow rate: 0.1 L/min (Peak)
    current analytical method: Gas Chromatography; GC/FID
    method reference: NIOSH Manual of Analytical Methods (NIOSH 1001 [23 KB PDF, 5 pages])
    method classification: Fully Validated

On-Site Sampling Techniques/Methods:

  • device: Pyrotec Tube
    manufacturer: Gastec
    model/type: 51
    sampling information: 1 stroke
    upper measurement limit: 480 ppm
    detection limit: approximately 10 ppm
    overall uncertainty: unknown
    method reference: on-site air secondary (manufacturer)

  • device: Pyrotec Tube
    manufacturer: Gastec
    model/type: 51L
    sampling information: 1 or 2 strokes
    upper measurement limit: 86 ppm
    detection limit: approximately 1 ppm
    overall uncertainty: unknown
    method reference: on-site air secondary (manufacturer)

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