Methyl isocyanate: the Bhopal gas

Bhopal was the site of the world’s worst industrial disaster, when on December 3, 1984, nearly 40 metric tons of methyl isocyanate (MIC) leaked from the Union Carbide pesticide plant and, being heavier than air, MIC settled on the ground. MIC is the smallest and most toxic of all isocyanates; it affected all life forms, killed nearly 8000 people within 48 hours by causing pulmonary edema, and produced lasting effects on more than 200,000 residents. There is no antidote against MIC, although sodium thiosulfate was administered in the mistaken belief that the culprit chemical was hydrogen cyanide. Studies done on experimental animals after the accident largely confirm what was observed on the Bhopal population. Nearly 40% of women pregnant at the time of the disaster lost their fetuses. Chronic effects include pulmonary, gynecological, ocular, neurological, and other complications. MIC metabolites are also toxic and some, like trimethylamine, exert selective toxicity on male progeny. Large quantities of highly toxic chemical waste stored in the factory premises have contaminated the soil and water. The Bhopal disaster revealed dangers inherent in chemical industries and the need for stringent regulations and supervision to ensure safety.