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Methylene bisphenyl isocyanate (MDI)

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

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:

Species Reference LC50 LCLo Time Adjusted 0.5-hr LC (CF) Derived value
Rat Bunge et al. 1977 369 mg/m3 ----- 4 hr 738 mg/m3 (2.0) 74 mg/m3
Rat Bunge et al. 1977 380 mg/m3 ----- 4 hr 760 mg/m3 (2.0) 76 mg/m3
Rat Woolrich 1982 178 mg/m3 ----- ? ? ?

Lethal dose data:

Species Reference Route LD50 (mg/kg) LDLo (mg/kg) Adjusted LD Derived value
Mouse Izmerov et al. 1982 oral 2,200 ----- 15,400 mg/m3 1,540 mg/m3
Rat Woolrich 1982 oral ----- 31,690 221,830 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.