Synonyms: MDI oligomer; polymeric MDI; polymeric
isocyanate; polymethylenepolyphenol isocyanate; polyphenyl
isocyanate Health Factors
OSHA IMIS Code Number:
Chemical Abstracts Service (CAS)
Registry Number: 9016-87-9
Chemical Description and Physical Properties:
molecular weight: ~400
flash point: 200°C
point: 200°C @760 mm Hg
Environmental Protection Agency (EPA)
carcinogenic classification: Group
D, not classifiable as to human carcinogenicity.
Potential symptoms: Itchy eyes, rhinitis, cough,
pulmonary secretions, chest tightness, dyspnea, wheezing, asthma.
Health Effects: Respiratory
sensitization---Asthma, hypersensitivity pneumonitis (HE9);
Irritation-Eye, Nose, Throat, Skin---Marked (HE14)
Affected organs: Respiratory system, skin, eyes
- Although OSHA has a PEL for methylene bisphenyl diisocyanate
(MDI) monomer (20 ppb ceiling), OSHA does not have a PEL for
polymeric MDI (PAPI).
- EPA’s inhalation reference concentration (daily inhalational
exposure likely to be without an appreciable risk of deleterious
effects during a lifetime) is 0.0006 mg/m3.
- Because toxicity is likely related to the very reactive
isocyanate (N=C=O) group and commercial preparations often
contain both MDI monomer and PAPI, exposure limit determination
based upon the mass concentration of the N=C=O groups in
polyisocyanates has been suggested.
- The MDI metabolites, N’-acetyl-4,4’-methylenedianiline and
4,4-methylene dianiline (MDA), have been measured in urine
samples from employees involved in the manufacture of
- Acid hydrolysis to release MDA from plasma proteins was used
to measure the half-lives of MDI-protein adducts in four
employees exposed to thermal degradation products of MDI-based
polyurethane. The half-lives of such adducts in plasma ranged
from 10-22 days.
- Chronic inhalation studies in rats with MDI (including PAPI)
in concentrations up to 6 mg/m3 reported increased lung weight,
interstitial fibrosis, broncho-alveolar hyperplasia and
adenomas, and in one high-dose rat, lung adenocarcinoma. In
contrast, chronic oral administration of the MDI metabolite,
MDA, caused carcinomas in the thyroid (rats and mice), liver
(female rats) and adrenals (male mice).
Date Last Revised: 07/24/2006
Monitoring Methods used by OSHA
- U.S. EPA Integrated Risk Information System: Methylene
Diphenyl Diisocyanate (monomeric MDI) and polymeric MDI (PMDI)
(CASRN 101-68-8, 9016-87-9).
- Baur, X.: Hypersensitivity pneumonitis (extrinsic allergic
alveolitis) induced by isocyanates. J.
Allergy Clin. Immunol. 95(5 Pt.
1): 1004-1010, 1995.
- Bello, D., et al.: Polyisocyanates
in occupational environments: a critical review of exposure
limits and metrics. Am. J. Ind. Med.
46(5): 480-491, 2004.
- Bonauto, D.K., Sumner, A.D., Curwick, C.C., Whittaker, S.G.
and Lofgren, D.J.: Work-related asthma in the spray-on truck bed
lining industry. J. Occup. Environ.
Med. 47(5): 514-517, 2005.
- Dalene, M., Skarping, G. and Lind, P.: Workers exposed to
thermal degradation products of TDI- and MDI-based polyurethane:
biomonitoring of 2,4-TDA, 2,6-TDA, and 4,4’-MDA in hydrolyzed
urine and plasma. Am. Ind. Hyg. Assoc.
58(8): 587-591, 1997.
- Feron, V.J., et al.: Chronic
pulmonary effects of respirable methylene diphenyl diisocyanate
(MDI) aerosol in rats: combination of findings from two
bioassays. Arch. Toxicol. 75(3): 159-175, 2001.
- Lamb, J.C., Huff, J.E., Haseman, J.K., Murthy, A.S. and
Lilja, H.: Carcinogenesis studies of 4,4’-methylenedianiline
dihydrochloride given in drinking water to F344/N rats and
B6C3F1 mice. J. Toxicol. Environ.
Health 18(3): 325-337, 1986.
- No authors listed: 4,4’-Methylenediphenyl diisocyanate and
polymeric 4,4’-methylenediphenyl diisocyanate. IARC Monogr. Eval. Carcinog. Risks Hum. 71(Pt. 3): 1049-1058, 1999. [381 KB PDF]
Laboratory Sampling/Analytical Method:
- sampling media: Coated Glass Fiber
Filter (37 mm open face) Coated with 0.1 mg
volume: 15 Liters maximum
flow rate: 1.0 L/min
analytical method: High Performance Liquid
reference: OSHA SLTC In-House File
method classification: Not Validated
note: Results may not reflect accurate
exposures to the polymeric forms of isocyanates. Keep filters
refrigerated until use.
condition: Column: TMS Chromegabond (C3); Mobile Phase:
45:55 Acetonitrile:Water that is 0.02 M Ammonium Acetate;
Detector Wavelength: 242 EX: 370 EM (Fluor)
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