On December 3, 1984, the Union Carbide pesticide plant in Bhopal India leaked methyl isocyanate gas. The gas is highly toxic, and as a result, a minimum of 3,787 died. Some estimates put the number as high as 16,000.

The Union Carbide India plant was built in 1969 to produce the pesticide, Sevin. As part of the process, methyl isocyanate was used to create the gas. The plant had three tanks that housed the gas. One of the three tanks became inoperable, and it was not possible to remove the gas from the tank.

On December 2 an attempt was made to clean the drain of the tank and instead resulted in water getting into the tank. This began a runaway reaction. By 12:40 Am December 3, 1984, the temperature in the tank that was supposed to be kept cold had reached 77 degrees and rising and a PSI of 40. The safety systems that were in place to protect tank all failed. At 12:50 AM the tank began emitting a toxic cloud.

It is estimated that 520,000 were affected by the gas. Of those 3,928 people officially died from the gas and over 50,000 more were injured. It was the worse industrial accident in history.