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Methyl Chloride

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 Emergency Response Guidebook: 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):
  • American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) (1992): 50 ppm (103 mg/m3) TWA; 100 ppm (207 mg/m3) STEL; Skin; A4
  • National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL): Appendix A - NIOSH Potential Occupational Carcinogens

Health Factors

  • Carcinogenic Classification:
  • 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
  • Notes:
    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):
  • 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 Analytical Methods (NIOSH 1001)
  • method classification: Fully Validated
On-Site Sampling Techniques/Methods:
  • 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)
  • 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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