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Methyl Isocyanate

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Overview


Methyl isocyanate (MIC) is an organic compound with the molecular formula C2H3NO, arranged as H3C-N=C=O. Synonyms are isocyanatomethane, methyl carbylamine, and MIC. It was discovered in 1888 as an ester of isocyanic acid. Methyl isocyanate is an intermediate chemical in the production of carbamate pesticides (such as carbaryl, carbofuran, methomyl, and aldicarb). It has also been used in the production of rubbers and adhesives. As a highly toxic and irritating material, it is hazardous to human health, and was involved in the Bhopal disaster which killed nearly 8,000 people initially and approximately 17,000 people in total.

Health Effects


Methyl isocyanate (MIC) is extremely toxic. The threshold limit value set by the American Conference on Government Industrial Hygienist was 0.02 ppm. MIC can damage by inhalation, ingestion and contact in quantities as low as 0.4 ppm. Damage includes coughing, chest pain, dyspnea, asthma, irritation of the eyes, nose and throat as well as skin damage. Higher levels of exposure, over 21 ppm, can result in pulmonary or lung edema, emphysema and hemorrhages, bronchial pneumonia and death. Although the odor of methyl isocyanate can not be detected at 5 ppm by most people, its potent lachrymal properties provide an excellent warning of its presence (at a concentration of 2-4 parts per million (ppm) subject's eyes are irritated, while at 21 ppm subjects could not tolerate the presence of methyl isocyanate in air).

The toxic effect of the compound was apparent in the Bhopal disaster, when around 42,000 kilograms of methyl isocyanate and other gases were released from the underground reservoirs of Union Carbide India Limited(UCIL) factory, over a populated area on December 3, 1984, immediately killing thousands and leading to the deaths of tens of thousands in subsequent weeks and months.

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