A Gas Leak in Bhopal Becomes One of the Worst Industrial Disasters

During the late hours of 2 December 1984, an escalating chemical reaction inside an underground tank at a pesticide plant in Bhopal, India, initiated one of the most catastrophic events in industrial history. The facility, operated by Union Carbide India Limited, had been constructed in 1969 to manufacture the pesticide carbaryl, sold under the brand name Sevin. A dedicated unit added in 1979 manufactured methyl isocyanate as a chemical intermediate. Over the years, the plant suffered recurrent safety problems, including accidental worker exposures to toxic substances like phosgene and methyl isocyanate between 1981 and 1984. By late 1984, the facility held large reserves of unused chemicals despite falling commercial demand.

The disaster centered on tank E610, which contained roughly forty-two metric tons of liquid methyl isocyanate. The vessel had lost its ability to sustain nitrogen gas pressure in late October, preventing operators from pumping out the chemical. When water inadvertently entered the tank during cleaning efforts late on 2 December, it triggered an uncontrolled exothermic reaction. Temperatures inside the tank soared, and internal pressure rapidly overwhelmed the tank's emergency relief valve. The plant's primary safeguards failed to arrest the release: a refrigeration unit designed to chill the chemical had been deactivated months earlier, a flare tower was disconnected for pipe maintenance, and the vent gas scrubber, meant to neutralize toxic discharges, did not contain the release.