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Methyl isocyanate

Methyl isocyanate (also isocyanatomethane, methyl carbonyl amine, MIC. C2H3NO; H3C-N=C=O) is a clear, colourless, sharp smelling liquid. It is highly flammable, boils at 39.1 C and has a low flash point.

It is extremely toxic and 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. Detectable odour and threshold levels for humans are triple the permissible exposure.

The toxic effect of the compound was apparent in the accidental release of around 40 tonnes of MIC over Bhopal, India on December 3, 1984.

It 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, adhesives.

It was discovered in 1888 as an ester of isocyanic acid.

See also: Bhopal Disaster, Pesticide poisoning