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May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)

Methylene bisphenyl isocyanate (MDI)

CAS number: 101–68–8

NIOSH REL: 0.05 mg/m3 (0.005 ppm) TWA,

0.2 mg/m3 (0.020 ppm) 10-minute CEILING

Current OSHA PEL: 0.2 mg/m3 (0.02 ppm) CEILING

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 0.051 mg/m3 (0.005 ppm) TWA

Description of substance: White to light-yellow, odorless flakes.

LEL: . . Unknown

Original (SCP) IDLH: 100 mg/m3

Basis for original (SCP) IDLH: The chosen IDLH is based on an analogy with toluene diisocyanate, which has an IDLH of 10 ppm. [Note: A concentration of 10 ppm methylene bisphenyl isocyanate is equivalent to about 100 mg/m3.]

Short-term exposure guidelines: None developed


Lethal concentration data:


SpeciesReferenceLC50 LCLoTimeAdjusted 0.5-hr LC (CF)Derived value
RatBunge et al. 1977 369 mg/m3-----4 hr738 mg/m3 (2.0)74 mg/m3
RatBunge et al. 1977 380 mg/m3-----4 hr760 mg/m3 (2.0)76 mg/m3
RatWoolrich 1982178 mg/m3-----? ? ?

Lethal dose data:


SpeciesReferenceRouteLD50 (mg/kg)LDLo (mg/kg)Adjusted LDDerived value
MouseIzmerov et al. 1982 oral2,200-----15,400 mg/m31,540 mg/m3
RatWoolrich 1982oral-----31,690221,830 mg/m3 22,183 mg/m3

Human data: None relevant for use in determining the revised IDLH.


Revised IDLH: 75 mg/m3

Basis for revised IDLH: The revised IDLH for methylene bisphenyl isocyanate is 75 mg/m3 based on acute inhalation toxicity data in animals [Bunge et al. 1977].


1. Bunge W, Ehrlicher H, Kimmerle G [1977]. Medical aspects of work with surface coating systems using the spraying technique. Zentralbl Arbeitsmed Arbeitsschutz Prophylaxe 4(spec. ed.):1-46 (in German). [From ACGIH [1991]. Methylene bisphenyl isocyanate. In: Documentation of the threshold limit values and biological exposure indices. 6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, pp. 978-980.]

2. Izmerov NF, Sanotsky IV, Sidorov KK [1982]. Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 63.

3. Woolrich PF [1982]. Industrial hygiene and medical control of TDI, MDI and PMPPI. Am Ind Hyg Assoc J 43(2):89-97.

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