A holding tank which stored this MIC overheated and due to it, it released the toxic fumes which rolled along the ground into the adjoining streets killing thousands of people. Around 800,000 people were living in Bhopal at that time and 2,000 died immediately, around 300,000 were injured and around 7,000 animals were killed or injured. Later the number of people who died was placed at 150,000.
This incident we now refer to as the Bhopal Gas Tragedy, which has also been called Hiroshima of the Chemical Industry one of the worst commercial industrial disasters in history. (Cohen) Pulmonary edema was diagnosed in most cases, but cough, chest pain, eyelid edema, unconsciousness were many of the ailments suffered by the people. Many suffered cardiac arrest and lung injury. Due to the hypothesized reactions that occurred within the storage tank as well as the surrounding atmosphere, it was thought that besides MIC other poisonous gases like hydrogen cyanide and phosgene might have played a significant role, though the company never provided any information on the exact chemical mixture.
It is through the blood and viscera of some victims which showed the cherry-red color that cyanide poisoning was suspected. A series of studies made five years later showed that many of the survivors were still suffering from one or several of the following ailments: partial or complete blindness, gastrointestinal disorders, impaired immune systems, post traumatic stress disorders, and menstrual problems in women. A rise in spontaneous abortions, stillbirths, and offspring with genetic defects was also noted. (The Bhopal Disaster). Let us explore how this tragedy took place.
The Union Carbide plant which was established in 1969 expanded in 1979 in order to produce carbayl. MIC is an intermediate in carbaryl. According to the post-accident analysis of the disaster, it was stated that the accident started when a tank which contained methyl isocyanate (MIC) leaked. MIC being a highly reactive chemical is used in the production of the insecticide carbaryl. Water entered this tank which contained about 400 cubic meters of MIC. When MIC mixed with water an exothermic chemical reaction took place which produced a lot of heat (over 200 degree C).
This resulted in the bursting of the safety valve of the tank due to the increase in pressure. The burst was so intensive that even the concrete around the tank broke and 20-30 tones of MIC were released in that one hour when the leak took place. This gas leak took place from a 30m high chimney, but this height was not enough to reduce the effect of the discharge. The high moisture content in the discharge while evaporating gave rise to a heavy gas which sank rapidly to the ground. Also the wind was weak and it changed its direction frequently which helped the gas cover more area in a short time.