| Case Name |
Leakage of toxic methyl isocyanate stored in a tank at a chemical plant |
| Pictograph |
|
| Date |
December 2, 1984 |
| Place |
Bhopal, India |
| Location |
Chemical factory |
| Overview |
In the night in December, 1984, a deadly poison MIC leaked from a chemical plant in Bhopal, India. It was carried by the wind, and the toxic MIC gas diffused throughout an urban district and over 3000 people were killed (up to 14410 persons) and about 350,000 persons were injured. Many people suffered from sequelae for a long time. The cause of the leakage was believed to be as follows. 1) Due to an operating error, off-specified distillate (MIC), which contained a lot of solvent chloroform, flowed into the tank. 2) Due to a mistake in rinsing work for vent piping, the water leaked into a storage tank. 3) Therefore, there was a following chain reaction. The temperature in the tank rose due to an exothermic reaction between MIC and water. Hydrogen chloride was generated by thermal decomposition of chloroform in the presence of water and iron was eluted. In addition, by a trimmer reaction of MIC by an iron catalyst caused the tank pressure and temperature to rise. Then, a safety valve operated. There was a management problem. Though three kinds of safety equipment were installed, all of them were not in use at that time.
In addition, as a hidden cause, the final product was being replaced by a new product, so the business was running a deficit. As a result, the top
managers including those of the parent company did not want to pay for costs of safety, education, and training. In other words, there was
a bad example of management without hazard management. |
| Incident |
From a storage tank of a chemical firm in Bhopal, which is in central India, methyl isocyanate (MIC), which is a deadly poison and an intermediate of a pesticide, leaked at night. Carried by a northwest wind, the leaked MIC gas diffused over the city and spread on the ground. No countermeasure was taken against the diffusion of toxic MIC gas because there was no previous warning and it occurred suddenly at night. Many citizens could not take refuge and received injuries. Refer to Fig4. |
| Processing |
Storage |
| Process Flow |
Fig2.Unit process flow
|
| Substance |
Methyl isocyanate, Fig3 |
| Type of Accident |
Leakage, environmental pollution, health hazard |
| Sequence |
On October 18th-22nd, 1984, at a distillation column of a manufacturing plant, high-temperature operations were carried out by mistake. As a result, the solvent chloroform, which is included in the distilled MIC, had exceeded by far the specification.
On October 23rd, the manufacturing plant shut down. Off-specification distillate had been stored in a storage tank.
On December 2nd, rinsing work for vent piping of storage tanks was carried out. For rinsing, a blind plate was not put in although the operation guide instructed that. It seemed that rinsing water leaked into the storage tank after rinsing.
23:00, the pressure in the storage tank rose.
23:30, leakage of MIC gas was detected.
00:45 on December 3rd, the runoff rate of MIC increased, and MIC gas nearly filled the tank.
02:30, the plant manager arrived at the site, and contacted the police.
03:30, the MIC gas started to diffuse outside the factory. |
| Cause |
Due to an operation error, water flowed into the MIC storage tank. An exothermic reaction between MIC and water was caused. By decomposing in the presence of water, the solvent chloroform in the distilled MIC generated chlorine ions. Chlorine ions corroded the stainless steel tank, and iron was dissolved out. A trimerization reaction of MIC was caused by an iron catalyst. Due to the exothermic reaction of the trimerization reaction, the following occurred. The temperature and pressure in the tank increased. As a result, the safety valve of the tank operated, and toxic MIC gas leaked out of the tank. Chloroform in the off-specification distillate produced during the operation decomposed in the presence of water, and hydrogen chloride was generated. The hydrogen chloride dissolved iron from stainless steel of the tank. Iron caused a trimerization reaction. A trimerization reaction caused by generation of hydrogen chloride had been known. |
| Response |
The shift leader was informed of the leakage, but he did not take any action. Spraying was done after the gas accumulated near the tank, but the spray water could not reach the tank. The plant manager arrived at the factory, and he contacted the police for the first time. Effective emergency measures were seldom taken. |
| Countermeasures |
As the factory has been closed since the disaster, no countermeasures were taken. Generally, the following are essential countermeasures.
1. Sufficient investigation and examination should be carried out on the hazard of toxic MIC.
2. Based on this, sufficient safety countermeasures should be taken for facilities and operations.
3. Safety education and training for employees should be provided thoroughly.
4. Sufficient communication with nearby inhabitants and administrative authorities should be carried out, and they should prepare to deal with an accident. |
| Knowledge Comment |
1. Even if the management situation is very bad, the minimum safety countermeasures and safety education must not be neglected. Safety is the minimum condition for an enterprise to exist.
2. Some of chemicals are highly toxic. Damage caused by toxic substances is enormous. Ensuring safety is an important duty of a company's management.
3. The parent company might be forced to take responsibility for the subsidiary company when it experiences a major disaster. The parent company is responsible for safety management of the subsidiary company. |
| Background |
The trigger that caused toxic MIC gas to be diffused was an error in the work and a mistake in operation of distillation on-stream, as described in the column "cause." Although the new operation manager directed inadequate work, the error was due to not only the manager but also operators.
Three kinds of safety equipment had been installed in the storage tank, and all of them had been stopped on the day. The boiling point of MIC was low, and it should be maintained below 0 °C to avoid evaporation. However, the refrigerator which was installed for cooling had been stopped since June. There was an opinion that it had been stopped to save energy. MIC gas evaporated and went outside the tank to the vent gas scrubber where MIC gas was absorbed by alkali during usual operation. However, the scrubber had also been stopped since October 22nd when the plant was shut down. The flare stack that burns all leaking gas, which is the final piece of safety equipment, had also been stopped for piping work. In short, there seems not to have been a consciousness of safety, while deadly poison chemicals of MIC were being handled. The leaking of water was also due to the same cause.
When the background is viewed, the pesticide that was the final product of MIC was being replaced with a pesticide of a different type. Therefore, the MIC factory was incurring a deficit, the company including the parent company did not make new investments, and the company did not pay attention to employees' safety, education, and training. Due to such a condition, the morale of the employees fell, and discipline became lax. Previous accidents had also happened, but their lessons were not used either. The irresponsibility of the parent company, which had given up its social responsibility to produce and store the deadly poison MIC, and the subsidiary, which was in charge of the operation, seems to be a basic cause. This disaster is a typical example in which hazards management was completely lacking. |
| Sequel |
Although the parent company of this accident was a major chemical firm in the U.S.A., it was absorbed by another major company, and it no longer exists. A major accident may lead to collapse of a major company. |
| Incidental Discussion |
The company claimed that the water was injected as an act of sabotage by the operator. This was denied in the courts. Initially, the number of fatalities was about 3500. CNN.com on November 28th, 2003, put the number of fatalities at 14410. Based on interviews with people who visited Bhopal at the end of 2004, it was over 20,000. It is said that although a person survives the acute phase, he will be chronically injured by the effects of exposure to MIC in the respiratory organs. The toxicity of MIC that leaked is far greater than that of phosgene. In an average work environment, the acceptable concentration per 8 hours in the U.S.A. is 0.02 ppm, and it is 1/500 of the acceptable concentration of cyan compounds. |
| Reason for Adding to DB |
The worst chemical disaster in the world caused due to inadequate management |
| Scenario |
| Primary Scenario
|
Poor Response to Change in Environment, Change in Environment, New Goods Coming, Poor Value Perception, Poor Organizational Culture, No Money No Safety Invest, Ignorance of Procedure, Disregard of Procedure, Wrong Indication, Usage, Maintenance/Repair, Wrong Operation Method, Malicious Act, Rule Violation, Stopping Safety Facilities, Bad Event, Chemical Phenomenon, Runaway Reaction, Secondary Damage, External Damage, Leakage, Bodily Harm, Death, It is said that over 20,000 person died, Bodily Harm, Sickness, Over 350 thousand person sickness, Damage to Society, Social Systems Failure, Loss to Organization, Social Loss
|
|
| Sources |
Ikuo Fukuyama. Bhopal disaster and its influence. SE second series. Study of accident. pp. 29-34 (1989).
Association monitoring the Bhopal disaster. Bhopal, Death City (1986)
Toshiyuki Miyake. Bhopal accident. Safety engineering. No.141, pp.346-354 (1987)
Yoichi Uehara. Terushige Ogawa. Fire prevention and explosion-proof control technology handbook. pp.12-22 (1998). p.147 (1987)
Osaka City fire fighting station. Case overseas. Examples of chemical emergencies. (1984 February - 1986 December)
Akio Akagi. Pesticide factory accident of India. Prevention time signal. No.142, pp.38-42 (1985)
|
| Number of Deaths |
26000 |
| Number of Injuries |
220000 |
| Financial Cost |
$470 million, compensation for damage. (About 610 hundred million yen). (by the India Supreme Court ruling in February, 1989) |
| Consequences |
Effluent gas diffused over about 40 square kilometers in a southeast urban district. Flora and fauna were also damaged. Many victims suffered from sequelae. |
| Multimedia Files |
Fig3.Chemical formula
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Fig4.Figure showing damaged area
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| Field |
Chemicals and Plants
|
| Author |
KOBAYASHI, Mitsuo (Office K)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
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