# NIOSH Pocket Guide to Chemical Hazards
Methyl iodide | CAS 74-88-4
CH3I | RTECS PA9450000
Synonyms & Trade Names Iodomethane, Monoiodomethane | DOT ID & Guide 2644 151
Exposure Limits | NIOSH REL: Ca TWA 2 ppm (10 mg/m3) [skin] See Appendix A
OSHA PEL: TWA 5 ppm (28 mg/m3) [skin]
IDLH Ca [100 ppm] | Conversion 1 ppm = 5.80 mg/m3
Physical Description Colorless liquid with a pungent, ether-like odor. [Note: Turns yellow, red, or brown on exposure to light & moisture.]
MW: 141.9 | BP: 109°F | FRZ: -88°F | Sol: 1%
VP: 400 mmHg | IP: 9.54 eV |  | Sp.Gr: 2.28
Fl.P: NA | UEL: NA | LEL: NA |
Noncombustible Liquid
Incompatibilities & Reactivities Strong oxidizers [Note: Decomposes at 518°F.]
Measurement Methods NIOSH 1014
Personal Protection & Sanitation Skin: Prevent skin contact Eyes: Prevent eye contact Wash skin: When contaminated Remove: When wet or contaminated Change: No recommendation Provide: Eyewash, Quick drench | First Aid (See procedures) Eye: Irrigate immediately Skin: Soap flush immediately Breathing: Respiratory support Swallow: Medical attention immediately
Respirator Recommendations NIOSH At concentrations above the NIOSH REL, or where there is no REL, at any detectable concentration: (APF = 10,000) Any self-contained breathing apparatus that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode/(APF = 10,000) Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained positive-pressure breathing apparatus Escape: (APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted organic vapor canister/Any appropriate escape-type, self-contained breathing apparatus
Exposure Routes inhalation, skin absorption, ingestion, skin and/or eye contact
Symptoms Irritation eyes, skin, respiratory system; nausea, vomiting; dizziness, ataxia; slurred speech, drowsiness; dermatitis; [potential occupational carcinogen]
Target Organs Eyes, skin, respiratory system, central nervous system Cancer Site [in animals: lung, kidney & forestomach tumors]
See also: INTRODUCTION