At Bhopal, three safety systems that could have stopped the gas were all out of action
Shortly after midnight on 3 December 1984, a storage tank at a pesticide plant in Bhopal began venting methyl isocyanate over a sleeping city. Refrigeration, a scrubber and a flare tower should have contained it, but none was working, and the public siren was switched off almost as soon as it sounded.
Union Carbide India Limited, majority-owned by the American Union Carbide Corporation, opened the plant in 1969 to make the pesticide Sevin, and added a unit in 1979 to produce methyl isocyanate, known as MIC, as an intermediate. Other makers had switched to a costlier route that avoided storing MIC. As pesticide demand fell in the early 1980s, production continued anyway and unused MIC piled up. Warnings were plentiful: a worker died in 1981 after a phosgene splash, the local journalist Rajkumar Keswani wrote that Bhopal was on the edge of a volcano, and several leaks followed in 1982.
Company rules said no MIC tank should be more than half full. Tank E610 held 42 tons and in late October 1984 lost the nitrogen pressure needed to pump it out. On the night of 2 December, water apparently got into the tank through a side pipe during cleaning, setting off a runaway reaction sped up by contaminants and rust. Rising pressure readings were dismissed as faulty instruments, and a response was put off until after a tea break. The refrigeration meant to chill the MIC had been shut down in 1982, its alarm disconnected; the flare tower was under repair and too small anyway, and the scrubber sat on standby. About 30 tonnes escaped in under an hour.
Communication failed as badly as machinery. The factory and public sirens had been separated in 1982, and company practice was to silence the public one to avoid alarming neighbours. Police calling the plant were twice told all was well. Hamidia Hospital was told first of ammonia, then phosgene, then simply MIC, a chemical its staff had never heard of and had no antidote for. Because the gas is about twice as dense as air, it hugged the ground, and children breathed in more of it.
Over 500,000 people were exposed, and no industrial accident anywhere is regarded as worse. The official immediate death toll was 2,259, though other estimates run far higher, and a 2006 government affidavit counted about 558,125 injuries. Union Carbide paid $470 million in a 1989 settlement, and in June 2010 seven former local managers were convicted of causing death by negligence.
Source: Bhopal disaster
