The World’s Deadliest Industrial Disaster Exposed 500,000 People to Toxic Gas and Claimed Thousands of Lives

Methyl isocyanate, a pungent, colorless and very flammable liquid used to produce pesticides, evaporates into a deadly gas almost instantly when exposed to air. In the early hours of December 3, 1984, it did just that, as around 40 tons of it spewed from the Union Carbide India Limited pesticide plant on the outskirts of Bhopal, India.

Dense, toxic gas hung low to the ground, burning the eyes and choking the throats of the city’s residents. At least 3,000 people were killed that night, and hundreds of thousands were left with cancer, pain and disease that would plague them for decades to come.

“People continue to think of Bhopal’s tragedy as one horrific night in 1984,” Apoorva Mandavilli wrote in the Atlantic. But the deadliest industrial disaster the world has ever seen neither started nor ended that year.

Instead, the seeds of the Bhopal disaster were sown some 15 years earlier, when Union Carbide Corporation, an American chemical company, built a pesticide plant in Bhopal in 1969. At the time, India was undergoing a green revolution as industry and agriculture joined forces to feed a growing population. Insecticides like carbaryl and aldicarb that the Bhopal plant manufactured were a major part of this modernization effort.

For the first decade, the Bhopal plant imported methyl isocyanate. But in 1980, the plant began manufacturing the essential pesticide production intermediary on site. Safety regulations and good practice, however, didn’t materialize at the Union Carbide plant.

The plant’s operation “was a case study in how not to do things,” Kumkum Modwel, a medical officer at the factory from 1975 to 1982, later told the Atlantic.

Halving the number of operators on duty and asking trainees to complete complex tasks left the Bhopal plant severely susceptible to a disaster like the one that happened in early December 1984.

Employees discovered a leak around 11:30 p.m. on December 2. But a supervisor scoffed at their concerns, dismissing the leaking liquid as just water and saying he’d deal with it after the next tea break. By that time, however, gas had built up, and a spare overflow tank, where employees should have directed the excess, was not as empty as protocol demanded.

Sirens began to blare. But these alarms—signaling an imminent and profoundly dangerous gas leak—sounded the same as the ones used about 20 times a week for practice drills in the facility. Understandably, employees of the factory didn’t immediately react.

Pressure in the tank continued to build until its safety valve broke. Methyl isocyanate and other chemicals shot into the air, carried by a brisk wind over an area of 15 square miles.

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Bhopal’s residents lay asleep when the cloud descended on them. Some fled for the hills in hopes of rising above the gas, but few could escape fully unscathed. Though the death toll is still disputed, Amnesty International estimates that “570,000 people were exposed to damaging levels of toxic gas,” with more than 22,000 deaths directly attributable to the leak over the years.

An investigation conducted by the New York Times later reported that the disaster “resulted from operating errors, design flaws, maintenance failures, training deficiencies and economy measures that endangered safety.”

Within a web of technical failures, human error and multinational corporations, blame was hard to place. But anger was widespread. When Warren Anderson, Union Carbide’s chair, visited Bhopal just four days after the disaster, he was arrested on charges of causing death by negligence. He promptly posted bail and left India for good, never facing trial.

Although the consequences of the disaster persist, the world’s attention eventually shifted away from Bhopal and its disaster. Just over a year later, a new deadly disaster—Chernobyl—captured imaginations, raising another set of impossible questions about how to avoid and respond to unthinkable environmental tragedies.

Eli Wizevich | | READ MORE

Eli Wizevich is a history correspondent for Smithsonian. He studied history at the University of Chicago and previously wrote for the El Paso Times.