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Health and Environment


Acute (Short-Term) Health Effects

  • MDI is a poison by inhalation. It is highly irritating to the eyes and respiratory tract and can cause coughing, wheezing, chest tightness, or shortness of breath. MDI is immediately dangerous to life and health at concentrations of 7.5 parts per million (ppm).
  • If MDI comes into contact with skin, it can irritate the skin and cause a rash.

Chronic (Long-Term) Health Effects

  • The chronic inhalation of MDI can result in shortness of breath, asthma, and other respiratory ailments.
  • MDI is an allergic sensitizer. The chronic inhalation of or skin contact with MDI may cause allergic reactions. The inhalation of MDI can cause an asthma-like allergy, where future exposure to very low levels of MDI result in asthma attacks with shortness of breath, wheezing, coughing, or chest tightness. Chronic skin contact with MDI can cause a skin allergy, where future exposures to very low levels of MDI result in itching or skin rash.
  • The International Agency for Research on Cancer (IARC) classifies MDI as a Group 3 carcinogen, not classifiable as to human carcinogenicity.

Life-Cycle Hazards

Manufacturers produce MDI using the "phosgenation process," where phosgene is an intermediary in the manufacture of MDI. MDI production begins with the condensation of aniline and formaldehyde, which forms diphenylmethane diamine. The phosgenation (addition of phosgene) of diphenylmethane diamine produces MDI.

  • Both formaldehyde and phosgene are considered high hazard chemicals in Massachusetts.
  • Formaldehyde is a probable human carcinogen and potential reproductive hazard.
  • Phosgene is a lethal gas at very low concentrations. To avert potential exposure manufacturers continuously monitor operating areas with a variety of alarm and shutdown systems.

Exposure Routes

Exposure to MDI, an intermediary chemical, occurs almost exclusively in the workplace through the inhalation of vapors and aerosols and dermal contact. Facilities using MDI must minimize worker exposure in the following manner:

  • Use MDI in closed systems. If a closed production system is infeasible, enclose operations and use local exhaust ventilation.
  • Take precautions to avoid MDI contact. If MDI contacts skin, wash immediately. If MDI exposure may exceed 0.005 ppm, use a Mine Safety and Health Administration/National Institute for Occupational Safety and Health-approved supplied-air respirator with a full facepiece.
  • Do not dry sweep MDI; use a vacuum or wet method to reduce dust during cleanup.

Environmental Defense Fund (EDF), 1999, "Chemical Profile: 1,1-Methylenebis(4-Isocyanatobenzene)" (New York: EDF; see webpage: http:/www.scorecard.org/chemical-profiles/); Richard J. Lewis, Sr. (ed.), 1993, Hazardous Chemicals Desk Reference (New York: Van Nostrand Reinhold); New Jersey Department of Health and Senior Services, 1998, "Hazardous Substance Fact Sheet: Methylene Bisphenyl Isocyanate" (Trenton, New Jersey; see webpage: http://www.state.nj.us/health/eoh/rtkweb/rtkhsfs.htm); and U.S. EPA, Office of Air Quality Planning and Standards, 1998, "4,4-Methylenediphenyl Isocyanate" (Washington, D.C.: U.S. EPA; see webpage: http://www.epa.gov/ttn/uatw/hlthef/methyl-d.html); Stanford Research Institute (SRI) International, Chemical Economics Handbook, "Diisocyanates and Polyisocyanates" (1998) and "Phosgene" (1997) (Palo Alto, California: SRI).