Methyl isocyanate

Its accidental release killed 2000 people in Bhopal, India in 1984. 
Just after midnight on December 3, 1984, a pesticide plant in Bhopal, India accidentally released approximately 40 metric tons of methyl isocyanate into the atmosphere. The incident was a catastrophe for Bhopal with an estimated 2000 casualties, 100,000 injuries, and significant damage to livestock and crops. The long-term health effects from such an incident are difficult to evaluate; the International Medical Commission on Bhopal estimated that as of 1994 upwards of 50,000 people remained partially or totally disabled. For the rest of this story, go to http://www.chemsafety.gov/lib/bhopal01.htm.