This research paper introduces the Bhopal plant gas tragedy disaster that happened in India, 1984: - Major causes and errors leading to multiple failures of the chemical plant are elaborated. - Main catastrophic consequences are discussed and classified in terms of casualties and fatalities, acute and chronic health effects, and toxic effects on soil and water. - Rehabilitation procedures adopted after the incident. - Preventive barriers that could have been adopted in order to reduce the likelihood of the disaster occurrence. If accidents are to be reduced, this needs maximum attention and an optimum risk management system.

1. Holy Spirit University of Kaslik - USEK
Faculty of Engineering
Department of Chemical Engineering
Analysis of BHOPAL Plant Gas Tragedy
Rita EL KHOURY Jean Noel SEMAAN Maya HARB
Project Supervisor Date
Dr. Rachad RAFEH Fall 2017-2018
Submitted on: 1 December 2017

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ACKNOWLEDGEMENT
First and foremost, we offer our deep sense of gratitude to all those who believed in us and
supported us throughout our educational years. We greatly appreciate all the assistance,
inspiration and encouragement that we got during our academic year that we feel so fortunate
to spending it at Holy Spirit University of Kaslik.
Afterward, we would like to express our sincere appreciation to Dr. Rachad RAFEH for
giving us the opportunity to write this report about the industrial disaster that occurred at the
Union Carbide pesticide plant in Bhopal, India. We are deeply glad and thankful for their
valuable guidance and for sharing their wisdom and expertise with us. It was a priceless time
to search, learn many new things and gain more knowledge.
Last but not least, we would like to thank everyone who helped us in a way or another to
finalize this project.

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ABSTRACT
At first, this paper introduces the Bhopal gas tragedy disaster that happened in India, 1984.
Then, the major causes and errors leading to multiple failures of the chemical plant are
elaborated. Furthermore, the main and catastrophic consequences are discussed and classified
in terms of casualties and fatalities, acute and chronic health effects, and toxic effects on soil
and water. This report shed lights also on the rehabilitation procedures adopted after the
incident along with the preventive barriers that could have been adopted in order to reduce
the likelihood of disaster occurrence. If accidents are to be reduced, this needs maximum
attention and an optimum risk management system.
Key words: gas tragedy, failures, barriers, risk management.

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Table of contents
ACKNOWLEDGEMENT........................................................................................................... 2
ABSTRACT................................................................................................................................... 3
Table of contents........................................................................................................................... 4
List of tables................................................................................................................................... 5
List of figures................................................................................................................................. 6
1. Introduction.............................................................................................................................. 7
2. Initiating Causes ...................................................................................................................... 8
3. Consequences..........................................................................................................................10
3.1 Effects on Human Health:............................................................................................10
3.2 Compensation and Legal Aspects: ............................................................................11
3.3 Soil and Water Contamination...................................................................................12
3.3.1 Soil Contamination....................................................................................................12
3.3.2 Ground Water Contamination................................................................................14
4. Rehabilitation Procedures....................................................................................................16
5. Preventive and Mitigation Controls....................................................................................17
6. Conclusion...............................................................................................................................18
REFERENCES............................................................................................................................19

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List of tables
Table 1 : Analysis of causes of failure ................................................................................... 9
Table 2 : Analysis of contaminants in different samples ...................................................... 15

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List of figures
Figure 1 : Initiating cause of Bhopal disaster......................................................................... 9
Figure 2 : The released gas cloud ........................................................................................ 11
Figure 1 : Bhopal plant after the disaster ............................................................................. 11

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1. Introduction
Management of hazards is becoming a crucial need in order to reduce the frequent
occurrence of major disasters such as Bhopal, Chernobyl, Mexico gas explosion, etc. A
disaster is a result from the combination of hazard, vulnerability, and insufficient measures to
reduce the potential chances of risk. The Bhopal accident was amongst the worst industrial
disasters of its time. The disaster occurred on the night of December 2, 1984 at the Union
Carbide India Limited pesticide plant in Bhopal, India. In the manufacturing process of this
plant, methyl isocyanate reacts with naphtol to produce carbaryl pesticides. Also, many
chemical compounds were manufactured in this plant such as phosgene, mono methylamine,
and methyl isocyanate. Despite that the plant was located near the residential areas and close
to the Bhopal railway bus stand, in 1979 the government gave the license to produce 5000
tons of carbaryl based pesticides in the existing premises. The production achieved between
1981 and 1983 decreased from 2704 tons to 1657 tons due to the reduction in demand for the
pesticides as the import of new products increased. Hence, the sales declined and the unit was
not making a profit anymore. Many technicians left to take up new positions elsewhere which
led to poor safety and maintenance practices. On the night of December 2, 1984, a leak of at
least 30 tons of highly toxic gases, methyl isocyanate gas and other chemicals, from the tank
into the atmosphere resulted in the exposure of thousands of people.
This report will shed lights on the series of events and the multiple threats that caused the
occurrence of this accident. Also, the consequences of this incident will be elaborated along
with the effects on human health, and the toxic materials found in soil and water. This paper
is an attempt to drive lessons for a better industrial risk management.

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2. Initiating Causes
First, a brief description of the manufacturing facility will be given so that the
sequence of events becomes clearer. The major chemical compound, MIC (methyl
isocyanate), is stored in underground stainless steel tanks. The tanks must be kept refrigerated
so that the temperature of storage is kept close to 0°C. Behind the tanks there is vent gas
scrubber used to neutralize the MIC in case of release. Then, there is a flare tower to burn the
remaining gases exiting the vent gas scrubber. Based on the safety manual, the scrubber
should be kept in active mode as long as the plant is operating. The routine release of gases
goes through the process vent header PVH, a line connected to the nitrogen pressurization
system, to the vent gas scrubber. In October 1984, in order to reduce operating costs, it was
decided to keep the vent gas scrubber in passive mode and to shut down the refrigeration
plant against safety manual instructions.
In December, as part of pipes cleaning procedure, the plant supervisor ordered washing the
MIC lines assuming that there was a blockage. The operator began washing out four lines in
the MIC storage area, and all these were connected to the PVH. While water was being
pumped under high pressure, he found that some lines were clogged. He reported the problem
to the supervisor. The supervisor, who was transferred from a completely different plant to
this unit only two weeks before the event, gave further instructions for rewashing and
inserting a slip blind so that water won’t go into the MIC tank. However, water accumulated
at height of 20 feet during the earlier washing and entered the tank containing 40 tons of
MIC. The absence of using a slip bind first is the triggering event.
Due to water entry, an exothermic reaction occurred which increased the temperature inside
the tank to over 200 ͦ C and raised the pressure. About 30 metric tons of MIC escaped from
the tank into the atmosphere and toxic gases covered more areas in a shorter period of time.
The safety valves burst due to the increase in pressure and the flare tower and the scrubber
vent gas were out of service for five months as illustrated in figure 1. As mentioned earlier,
the refrigeration is switched off to save money which helped in the increase in temperature.

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Figure 1: Initiating cause of Bhopal disaster
Several other causes of failure contributed in this gas leakage are represented in table 1.
Type of Failure Basic Causes
Technical - Design failure and poor maintenance
- Absence of HAZOP studies
Operator - Poor personnel and training
- Over stress
- Poor communication between shifts
Management - Poor risk assessment practices
- Lack of formalization
- Failure to anticipate the catastrophic
potential
Government - Absence of clear policy and
regulations
- Lack of controlling land use
Table 1: Analysis of causes of failure

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3. Consequences
The pesticide plant was surrounded by houses and towns, leading to more than
600,000 people being exposed to the deadly gas cloud that night. The dense gas cloud
contained phosgene, hydrogen cyanide, carbon monoxide, hydrogen chloride, oxides of
nitrogen, carbon dioxide, etc. The gases stayed low to the ground, causing victims throats and
eyes to burn, inducing nausea, and many deaths. A government official declaration in 2006
stated that the leak caused 558,125 injuries including 38,478 temporary partial injuries and
approximately 3,900 severely and permanently disabling injuries. Estimates of the death toll
vary from as few as 3,800 to as many as 16,000, but government figures refer to an estimate
of 15,000 killed over the years. The toxic substance spread its way in and around the
neighborhood located near the plant causing up to 10,000 deaths in first three days and
thousands of animals perished in the disaster as well, poisoned by the huge gas leak. The
wide variety of symptoms observed at Bhopal has been due to the exposure of a large number
of toxic substances in varying concentrations at different locations. Human rights groups say
that thousands of tons of hazardous waste remain buried underground, and the government
has conceded the area as contaminated. Many of those who were exposed to the gas have
given birth to physically and mentally disabled children. For decades, survivors have been
fighting to have the site cleaned up. However, there has been no long-term epidemiological
research which conclusively proves that birth defects are directly related to the drinking of
the contaminated water.
3.1 Effects on Human Health:
 Acute, short term health effects:
- Respiratory Disorders: irritation to the lungs, causing coughing and/or shortness of
breathing, burning in the respiratory tract.
- Vomiting and stomach pain.
- Severe eye irritation and blindness.
- Feeling of suffocation

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 Chronic, long term health effects:
- Reproductive system: It may damage the growing fetus. Also affect fertility in men
and women.
- Effect traces of many toxins were found in the Brest Milk of mothers and were in turn
transmitted to the recipient babies.
- Immune and neurological disorders.
- Cardiac system failure.
3.2 Compensation and Legal Aspects:
- Compensation of $470 millions: around $500 per dead
- Twenty years of passiveness.
- Case was reviewed and put up in American Court.
- In order to provide safe drinking water to the population around the factory, the
government put a scheme for treatment and improvement of water supply.
- Supreme Court was directed to take immediate steps for disposal of toxic waste lying
around and inside the factory.
Figure 2: the released gas cloud Figure 3: Bhopal plant after the disaster

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3.3 Soil and Water Contamination
Soil and ground water were also contaminated by several toxic substances such as heavy
metals and chlorines at various degrees. SHRI CHAUHAN, a former employee of Union
Carbide and currently with District's Industrial Area Dept, says that: “in the compound of the
UCL, about 25 chemicals and hazardous wastes lying in there. They are Methyl Isocyanate,
Methyl Chloride, Carbon Tetra chloride, Methanol, Phosgene, Chlorine, Tar coal, Mercury,
Naphthalene and many more.”
3.3.1 Soil Contamination
Nickel, Chromium, Mercury and Lead were found in soil samples taken from different
areas of the plant. The tests showed that Nickel and Chromium were the most found heavy
metals in the samples taken. On the other hand, Mercury was mostly found in the alpha-
naphthol and the Pan Filter sites.
These metals caused several toxicological effects, as presented below:
 Nickel:
- Metallic Ni and its alloys are designated as carcinogens.
- Nickel refining plant workers are present to a higher risk of lung cancer than
normal people.
- Women exposed to Ni, may be at complicated pregnancy risk and even leading to
birth defects and malformations e.g. cardiovascular and musculoskeletal.
- Chronic and long term Ni exposure can lead to chronic bronchitis and lungs
malfunction.
50g/L is the maximum acceptable Nickel dosage for human consumption, as set by the
European Union directive.
 Chromium:
- It is corrosive and considered as allergen (skin allergies).
- Chromium’s long term exposure leads to lung cancer
50g/L is the maximum acceptable Chromium dosage for human consumption, as set by
the European Union directive.

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 Mercury:
- Mercury is very toxic and dangerous.
- There are no removal ways of mercury once it penetrated the human body.
- Hg affects the function of the kidneys causing renal damage.
- Chronic and long term Hg exposure may disturb the nervous system leading to
tremors, spasms, loss of memory and depression.
1g/L is the maximum acceptable Chromium dosage for human consumption, as set by the
European Union directive.
 Lead:
- Lead, when ingested can harm the human body.
- Lead causes hypertension, as well as neurotoxicity.
On the other hand, a significant amount of pesticides were found in soil samples. HCH
pesticide concentrations were 9 mg/Kg in the soil samples taken and their average
concentration was 1.60 ppm. HCH presents two forms of isomers: gamma- HCH and beta-
HCH. Gamma’s form dosage exceeded Beta’s.
The HCH pesticides different consequences on the human body were several:
- Humans are considered sinks for these toxic chemicals, because they rank as the
highest level.
- HCH gets bio-concentrated when ingested, especially in infants and breast milk.
- It presents toxic effects on fertility and reproductive system.
- It can lead to lung, liver and endocrine cancers.
Furthermore, the investigations showed that Volatile Organic Compounds such as
Dichlorobenzene, 1, 3, 5-Trichlorobenzene and Tetra ChloroBenzene were present in all the
samples. The predominant contaminant was the Dichlorobenzene. The total dose found in
the soil was 5.86 mg/Kg and its mean was to some extent lesser than 1 mg/Kg. Every soil
sample tested in the plant revealed positive results.

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Those compounds are considered as toxic substances, because they induce several problems:
 Dichlorobenzene:
- It enters the human body by inhalation.
- It causes: depression, headache, anorexia, liver atrophy, eye irritation, etc.
 1,3,5-Trichlorobezene:
- It enters the body by inhalation.
- It damages the liver, kidneys as well as the thyroid.
 Tetra ChloroBenzene:
- The exposure of TCB is done through food.
- It damages the liver, kidneys as well as the thyroid.
- Chronic exposure to TCB leads to chromosomal aberrations.
3.3.2 Ground Water Contamination
Similarly to the soil, ground water was also found to be contaminated by different toxic
chemicals:
- Heavy Metals:
Nickel was the principal contaminant among all ten ground water samples, presenting
a value of 1.0990 ppm.
- Pesticide HCH
HCH found in the ground water samples was 0.0898 mg/L, having a mean value of
0.011 ppm. The water tested from the factory premises showed 0.115 mg/Kg of the
pesticide HCH. The level of pesticides found in the factory’s premises is ten times
greater than those found are in the residential areas around the plant.

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- Volatile Organic Compounds:
The average doses in ground water samples of the residential areas were found to be
0.050 mg/Kg; however the samples from the plant premises contained 0.0331 mg/L
of volatile organic compounds.
- Halo-organics:
Dichloromethane and Chloroform were found in all eight ground water samples
taken. Dichloromethane concentration values were two times higher than
Chloroform.
Table 2: Analysis of contaminants in different samples
The soil and ground water of residential areas, the factory, the vegetables and the breast milk
were highly affected by this disaster to various degrees. The vegetables grown in the interior
of a residential area opposite to the front gate of the factory had the ability to absorb these
toxic chemicals and transfer to the next level of a food chain.
Although evaporation ponds were present to collect chemical wastes, the possibility of
overflowing during rainfall and contaminating surrounding areas was high.

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4. Rehabilitation Procedures
 Occupational rehabilitation:
33 of the 50 planned work sheds for gas victims started. It is estimated that 50,000
person need alternative jobs and less than 100 gas victims have found regular
employment under the government scheme.
 Habitation rehabilitation:
2,486 flats in two and four buildings were constructed outside Bhopal; however water
did not reach the upper floors. In order to provide safe drinking water to the
population, there was a system for improvement of water supply. Infrastructures were
missing for at least a decade.
 Environmental rehabilitation:
When the factory was closed, pipes, drums and tanks were sold. Isolation material
was falling down and spreading. The area around the plant was used as a dumping
area for hazardous chemicals. Formal statements were issued that air, water,
vegetation and foodstuffs were safe within the city. At the same time, people were
informed that poultry was unaffected, but were warned not to consume fish.
 Health care:
In the immediate aftermath of the disaster, the health care system became
tremendously overloaded. Within weeks, the State Government established a number
of hospitals, clinics and mobile units in the gas affected area. In 1994, there were
approximately 1.25 beds per 1000, compared to the recommendation of the World
Bank of 1 bed per 1000 in developing countries.

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5. Preventive and Mitigation Controls
The most critical reasons for the occurrence of the errors are the corporate level
failure of safety management systems and procedures. If regular rehearsal of emergency
procedures had been in force in Bhopal, many of the plant equipments and operator
inadequacies could have been corrected. Analysis of the Bhopal accident shows that
organizational failures are the most critical ones that need attention if accidents are to be
avoided.
In order to reduce the likelihood of the incident, some preventive barriers could have been
adopted:
- Supervisors could have been placed on night shifts.
- The readings and feedback of equipments could have been taken for every one hour.
- There should have been 4 stage backup systems instead of a one manual backup
system.
- Proper maintenance and servicing of flare towers, pressure valves, and gas scrubber
must have been made.
- Strict regulations and methods must have been used according to the manual
- Proper pressure gauges should have been used to maximize the safety.
- Formulation of a detailed HAZOP or HAZAN study on the completed installations by
internal staff and it should be used for safety management of day-to-day operations.
Such work has to be done by the people who are directly involved with the plant as
only they are likely to have the detailed knowledge required based on work
experience.

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6. Conclusion
It is essential that decision makers perceive and estimate the hazards arising out of a
project at the project formulation phase. Risk management has to start at the site selection and
project feasibility analysis phase. This comprehensive approach is the only way to have
cheaper and safer plants. Thinking about the hazards after the commissioning of the project is
likely to minimize the extent of hazards whereas the anticipate-and-prevent approach is likely
to provide minimum cost options, if initiated at the project formulation phase itself.
A conceptual framework for accident analysis indicates that in most complex systems 80 to
85% of the failures are in the management and organization aspects of the system and only
15-20% of the failures are due to human error. The analysis of the Bhopal accident, presented
here corroborates the conclusion that organizational or corporate level failures are the most
critical ones that need attention if accidents are to be avoided. The most important
prerequisite for accident prevention is the top management commitment to safety. Accident
prevention needs not to be treated as an expensive add-on facility but it has to be an integral
part of management and organizational objectives. When hazardous facilities are to be built
in developing countries, the levels of safety to be achieved must be higher.
To sum up, risk management has to be started along with the preparation of the feasibility
report as an inherent part of the project appraisal procedure, for all hazardous chemical
facilities. This has to be put into operation along with the running of the plants through
detailed safety management practices supported by appropriate corporate safety commitment.

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REFERENCES
[1] B. Bowonder, “An analysis of the Bhopal accident,” Project Appraisal, 2:3,157-168,
(1987).
[2] SRISHTI, “Surviving Bhopal, toxic present-toxic future”, report on human and
environmental chemical contamination around the Bhopal disaster site, January 2002.
[3] Yusuf S.A., “Bhopal gas tragedy”, Saint Philomena’s college,