Twenty-five years ago this month, the worst accident in the history of the chemical industry occurred — a leak of highly toxic methyl isocyanate (MIC) gas at a Union Carbide pesticide plant in Bhopal, India, that killed thousands of people. Industry learned many lessons; experts wrote many reports. Here, we’ll look at some of the wider lessons learned rather than the narrow points on which most reports concentrated.
The story started in 1974, 10 years before Bhopal, when a large leak of hydrocarbon exploded at a Nypro (UK) plant at Flixborough, U.K., killing 28 people. The leak was large because only 6% of the hydrocarbon fed to the plant was converted; 94% had to be recovered and repeatedly recycled. The most important recommendation made afterward was that we should look for ways to reduce the amount of hazardous materials in a plant, a process called intensification or minimization. The slogan was: “What you don’t have can’t leak.” This thought didn’t occur to most commentators or the official inquiry. Reducing inventory in the Flixborough process isn’t easy. One company started but then abandoned a research project after realizing there was excess capacity in the process, a stage in manufacture of nylon.
The Bhopal disaster wouldn’t have occurred if the plant managers had known about and then adhered to the recommendation made after Flixborough. MIC wasn’t a raw material or product but an intermediate. Storing it was convenient but nonessential. It could have been used as it was made — then the worst leak would have been a few kilograms from a broken pipe rather than a hundred tons from a tank. This time the chemical industry paid attention; within a year many companies had reduced or eliminated their hazardous intermediates stocks and used the materials as they made them.
The “Don’t Have” concept can be applied more widely. If chemicals we don’t have can’t leak, people who aren’t there can’t be injured or killed. The human toll at Bhopal was so high because a shanty town had grown up near the plant. It’s difficult in a country like India to control development but necessary nevertheless to prevent people from living too close to hazardous sites.
A 2005 explosion at a BP refinery in Texas City, Texas, killed 15 people and harmed 170. One reason for the large number of deaths and injuries was that temporary buildings used by maintenance workers were close to the explosion site. If the buildings had been placed further away from equipment containing hazardous materials — a recommendation that often has been made — the toll would have been lower.
Similarly, if no buildings are nearby, they can’t be damaged or destroyed by explosions. The worst peacetime explosion in England occurred at Buncefield in 2005 when gasoline overflowed though the vent at the top of a large storage tank. The ensuing explosion extensively damaged the storage area and a large number of offices and small factories on an adjoining site.
The underlying cause of Buncefield was that all the people and organizations involved in design, operations and maintenance were unaware of similar explosions in Newark, N.J., in 1983 [1,2,3], St. Herblain, France, in 1991 , Naples, Italy, in 1995 , and elsewhere (other incidents easily can be found by googling “gasoline spill”). They believed cold gasoline couldn’t explode in open air. The group of oil companies that owned the storage depot claimed an explosion of cold gasoline in open air never before had occurred. Damage at Buncefield, however, was more extensive than at Newark and elsewhere.