Immediately Dangerous to Life or Health Concentrations (IDLH)
CAS number: 624–83–9
NIOSH REL: 0.02 ppm (0.05 mg/m3) TWA [skin]
Current OSHA PEL: 0.02 ppm (0.05 mg/m3) TWA [skin]
1989 OSHA PEL: Same as current PEL
1993-1994 ACGIH TLV: 0.02 ppm (0.047 mg/m3) TWA [skin]
Description of substance: Colorless liquid with a sharp, pungent odor.
LEL: . . . 5.3% (10% LEL, 5,300 ppm)
Original (SCP) IDLH: 20 ppm
Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by ACGIH  that the rat 2-hour LC50 is 21 ppm [Kimmerle and Eben 1964].
Short-term exposure guidelines: None developed
ACUTE TOXICITY DATA:
Lethal concentration data:
|Species||Reference||LC50 (ppm)||LCLo (ppm)||Time||Adjusted 0.5-hr LC (CF)||Derived value|
|Dodd et al. 1986Dodd et al. 1986
Dood et al. 1986
Kimmerle & Eben 1964
|6 hr6 hr
|14 ppm (2.3)28 ppm (2.3)
12 ppm (2.3)
34 ppm (1.6)
|1.4 ppm2.8 ppm
Lethal dose data:
|Species||Reference||Route||LD50 (mg/kg)||LDLo (mg/kg)||Adjusted LD||Derived value|
|MouseRat||Vernot et al. 1977Vijayarachavan & Kaushik 1987||oraloral||12051.5||———-||354 ppm152 ppm||35 ppm15 ppm|
Human data: Volunteers experienced eye irritation and lacrimation after 1 to 5 minutes at 2 ppm, with more marked irritation at 4 ppm; exposures were unbearable at 21 ppm [Kimmerle and Eben 1964]. In another study, volunteers noted eye irritation and lacrimation at 5 ppm in less than 50 seconds [Mellon 1963].
|Revised IDLH: 3 ppmBasis for revised IDLH: The revised IDLH for methyl isocyanate is 3 ppm based on acute inhalation toxicity data in humans [Kimmerle and Eben 1964; Mellon 1963].|
1. ACGIH . Methyl isocyanate. In: Documentation of the threshold limit values. 3rd ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, p. 167.
2. Dodd DE, Fowler EH, Snellings WM, Pritts IM, Baron RL . Acute inhalation studies with methyl isocyanate vapor. I. Methodology and LC50 determinations in guinea pigs, rats, and mice. Fundam Appl Toxicol 6:747-755.
3. Kimmerle G, Eben A . Zur toxicitat von methylisocyanat und dessen quantitativer bestimmung in der luft (Toxicity of methyl isocyanate and its quantitative determination in the air). Arch Toxikol 20:235-241 (in German).
4. Mellon . Special report 26-23. Pittsburgh, PA: Mellon Institute (March 13, 1963).
5. Vernot EH, MacEwen JD, Haun CC, Kinkead FR . Acute toxicity and skin corrosion data for some organic and inorganic compounds and aqueous solutions. Toxicol Appl Pharmacol 42:417-423.
6. Vijayarachavan R, Kaushik MP . Acute toxicity of methyl isocyanate and ineffectiveness of sodium thiosulphate in preventing its toxicity. Indian J Exp Biol 25:531-534.