Methemoglobinemia resulting from exposure in a confined space: Exothermic self-polymerization of 4,4'-methylene diphenyl diisocyanate (MDI) material.
A worker attempting to remove solidified material inside a confined space (storage tank) suffered severe methemoglobinemia and almost died. The tank contained liquid 4,4'-methylene diphenyl diisocyanate monomer that had solidified after an equipment power failure caused excessive heating. Wearing a full-face elastomeric air-purifying respirator and Tyvek® coveralls, the worker used pneumatic air hammers to break up the solid material. After two tank entries totaling slightly less than one hour, the worker complained of headache and dizziness and within two hours of exiting the tank, he was admitted to the hospital in severe respiratory distress. During his eight-week hospital course, he suffered a cardiac arrest among other complications. An investigation into the cause of the worker's illness used onsite gas chromatography-mass spectrometry which identified aniline and p-toluidine vapor within the tank, attributable to overheating that led to formation of the solid material. Both are well-known causes of methemoglobinemia, and had the initial characterization of the confined space atmosphere adequately identified the hazards present appropriate engineering controls and personal protective equipment could have allowed the tank entrant to work safely in the space.
a U.S. Department of Labor - OSHA , Health Response Team , Sandy , Utah.
Philip A
PA
Smith
a U.S. Department of Labor - OSHA , Health Response Team , Sandy , Utah.
Jeffrey
J
Lodwick
b U.S. Department of Labor - OSHA , St. Louis Area Office , St. Louis , Missouri.
Joe
J
Dartt
c U.S. Department of Labor - OSHA , Office of Occupational Medicine and Nursing , Washington , D.C.
Jenny R
JR
Amani
c U.S. Department of Labor - OSHA , Office of Occupational Medicine and Nursing , Washington , D.C.
Kathleen M
KM
Fagan
D000328:Adult; D020378:Confined Spaces; D006801:Humans; D017953:Isocyanates / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*; D008297:Male; D008708:Methemoglobinemia / Q000139:chemically induced*; D009784:Occupational Diseases / Q000139:chemically induced*; D016273:Occupational Exposure / Q000032:analysis*; D014481:United States; D014489:United States Occupational Safety and Health Administration; D001559:Benzhydryl Compounds
D017953:Isocyanates; C005969:4,4'-diphenylmethane diisocyanate; D001559:Benzhydryl Compounds
Aniline; MDI; methemoglobinemia; methylene diphenyl diisocyanate; p-toluidine; thermal degradation