Methyl isocyanate pulmonary toxicity

Methyl isocyanate, producing toxic pulmonary oedema... 

Sriramachari S, Jeevaratnam K Comparative toxicity of methyl isocyanate and its hydrolytic derivatives in rats. II. Pulmonary histopathol-ogy in the subacute and chronic phases. Arch Toxicol 69 )-A5-5, 1994... 

Toxicology. Methyl isocyanate (MIC) is an irritant of the eyes, mucous membranes, and skin at higher doses it is extremely toxic and can cause death from pulmonary edema. 

One of the worst industrial accidents occurred in Bhopal, India, on December 2 and 3, 1984. It was due to the leakage of methyl isocyanate (MIC) released from the Union Carbide pesticide manufacturing plant. More than 3,000 people who resided in areas adjacent to the manufacturing plant died within a few hours after exposure to MIC. Death was attributed to severe pulmonary toxicity, followed by... 

Dutta, K.K., Gupta, G.S.D., Mishra, A., Joshi, A., Tandon, G.S., Ray, P.K. (1988). Inhalation toxicity studies of methyl isocyanate (MIC) in rats. Part I Pulmonary pathology and geno-toxicity evaluation. Indian J. Exp. Biol. 26 177-82. 

The world s worst industrial disaster occurred in Bhopal, India, in 1984 in which nearly 40 metric tons of methyl isocyanate was released from a pesticide plant killing over 3000 people. Most deaths resulted from pulmonary edema within 3 days of accident. Many follow-up studies indicated pulmonary, ophthalmic, neurological, reproductive, immunologic and hematologic toxic effects among the survivors. 

PU are compounds formed by reacting the polyol component with an isocyanate compound, typically toluene diisocyanate (TDI) methylene diisocyanate (MDI) or hexamethylene diisocyanate. Polyols are relatively non-toxic (i.e., polyether type polyols are found to be safe, because they are low in oral toxicity with almost no irritation effect to the eyes and skin), however, isocyanates are highly toxic and the product can have a significant toxicity if remnants of isocyanate are in it, which manifests itself mainly as a respiratory (as well as a dermal) hazard. Exposure to the vapour of isocyanates directly may cause irritation for the eyes, respiratory tract and skin. Such an irritation may be too severe to produce bronchitis and pulmonary oedema. As health hazards of isocyanates are considered, one immediately remembers one of the worst industrial disasters of the 20th century, that occurred in Bhopal, India, because of the toxic cloud of methyl isocyanate was released accidentally from the Union Carbide pesticide factory in December 1984. An estimated 3,000 people died immediately with a final of some 20,000, most suffocating from the cloud s toxic chemicals, and some 50,000 were injured, most were residents living near the plant. 

The large number of casualties from chlorine and phosgene exposure during World War I showed that survivors showed long-term respiratory disorders with chronic bronchitis and emphysema, the most common conditions, followed by pulmonary fibrosis. The Bhopal incident in India (see Chap. 10) has also shown evidence of long-term respiratory disorders following exposure to the toxic industrial pulmonary oedemagen methyl isocyanate. 

Affected casualties suffered from initial acute airway irritation and inflammatory changes and later from toxic pulmonary oedema. Although the cloud may have contained contaminants and by-products including hydrogen cyanide and oxides of nitrogen, there is little doubt that the main effects were caused by methyl isocyanate which is a known pulmonary oedemagen. Following the release, about 400,000 persons fled the city in a totally uncontrolled evacuation. The evacuation of those who were actually exposed was compounded by a panic evacuation of residents who lived more than 10 km from the release site. 

Important Point Methyl isocyanate is an organic chemical that is used in the production of pesticides. Methyl isocyanate, commonly referred to as MIC, is extremely toxic to humans. Short-term exposure may cause death or adverse health effects, including pulmonary edema (respiratory inflammation), bronchitis, bronchial pneumonia, and reproductive effects. 

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