Bhopal gas tragedy, which occurred on the midnight of 3rd December
1984 in the Indian city of Bhopal, is considered as the world’s worst
industrial disaster. According to the World History Project, thirty-two tons of
poisonous methyl isocyanate (MIC) gas leaked from the MIC storage tank of the
Union Carbide India Ltd. pesticide plant. Over 500,000 people living in the
nearby towns were exposed to the lethal Methyl Isocyanate gas and according to
a report by researcher Ingrid Eckerman, over 8,000 people lost their lives
during the initial weeks. The cause of the disaster is still a topic of debate
with the Indian government alleging that slack management combined with shoddy
maintenance caused the gas leak while Union Carbide in its defense has claimed
that the disaster was an act of sabotage by vested interests.
The plant was built in 1969 by
the Indian subsidiary of the multinational company Union Carbide Corporation
(UCC) which is headquartered in TX, USA. Before the incident, the plant was
used to manufacture a different pesticide called ‘Sevin’. Even before the
fateful gas leak, the plant has had a history of accidents in which multiple
employees had either suffered severe injuries or had died. For example, in
January 1982, a phosgene leak exposed 24 workers, all of whom had to be
admitted to a nearby hospital. Subsequent findings revealed that workers had
not been ordered to wear protective masks. A month later, a MIC leak affected
18 more workers.
Chemicals abandoned at the
plant continue to pollute the environment and ground water resources in the
nearby areas. In 2004, 20 years after the tragedy took place, a BBC Radio 5
broadcast reported the site to be contaminated with toxic chemicals. It further
stated that water samples collected from nearby were contaminated by more than
500 times the maximum limits recommended by the World Health Organization.
The Bhopal tragedy has taught
all of us a very big lesson in risk management. I believe that had there been
proper safety protocols and risk mitigation strategies in place, a disaster of
this magnitude could have been avoided, or at least curtailed. For this
research review paper, the author will limit the scope to analyzing the root
cause of the Initiating Event of the gas leak along with the kind of lapses on
part of the plant management and local civic authorities and the consequences
of their actions. The fact that even after more than three decades there is no
conclusive theory on what caused the gas leak, it is important to analyze all
the different versions that are presented by established researchers.
The UCIL facility in Bhopal, India was
a manufacturing site for carbamate pesticides that had similar design and
technical specifications to the one in West Virginia. MIC was used as a raw
material for these pesticides and the plant stored a large quantity of MIC on
site. MIC by itself is a very volatile liquid with a pungent odor. It is highly
flammable and potentially explosive when reacts with air. With water, it forms
an exothermic reaction to form toxic products of methylamine and carbon dioxide.
The boiling point of MIC is very low at 39°C and its vapor density is more than
that of air, which makes is volatilize readily. Due to its low boiling point,
it is stored between –10°C and 0°C to maintain a low vapor pressure and prevent
of the Plant
illustrates the pesticide production facilities at which the MIC was produced
in the production plant and consumed on site as a raw material in the pesticide
plant (MIC consumer).
The plant design
required MIC storage to be kept at minimum volumes. A caustic scrubber was
provided to neutralize any MIC emissions from the storage tanks and a flare was
present to burn vented MIC. A refrigeration system was also in place to keep
the stored MIC cold & decrease its reaction rate with water.
Gas Leak Initiating Event: Operator
Error or Sabotage?
Any accident begins with an initiating event. The
same for Bhopal was the introduction of a large amount of water into the tank (~
500 liters). MIC is generally a stable compound, but is very reactive with
water and generates an exothermic reaction, which generates a large amount of
heat as by-product. As the reaction of water and MIC took place, the tank’s
temperature and pressure started increasing, slowly at the beginning and then
accelerated quickly until the venting began.
The cause of the disaster (Initiating Event) is
still a debate with different sides arguing differently. One of the theories
places the blame on negligence of plant operators by arguing that in another
part of the plant, they did not properly isolate the header while water washing
the vent header which allowed water to reach the MIC tank and react with it. A
second theory looks at the angle of sabotage from one of the many disgruntled
workers in the plant. The plant was running in losses and there had been a
considerable of staff reductions leading up to the accident. There was
widespread mistrust between workers and the management and its highly possible
that one of the workers intentionally injected water into the tank, probably to
ruin that batch of MIC and not knowing of the larger consequences (D’Silva
2006; Kalelkar 1988).
A third theory blames the plant management for
bypassing key safeguards and preventive measures that act as standard safety
protocol measures. For example, the most basic safeguard measure dictates that
the quantity of MIC stored should be minimal and according to standard
operating procedures, two out of the three tanks should have been empty and the
third tank should have been at less than 50% of the total capacity. However,
the actual level in the ill-fated tank was almost 70% on the day of the
disaster. Moreover, there was also smaller amounts of MIC present in one of the
other tanks. Such high amounts of MIC present in the storage tanks limited the
plant management’s options to restrict the exothermic reaction at the time of
the gas leak. Secondly, a refrigeration system which was present to keep the
MIC at 30°F (well below its boiling point) had been turned off just
months before the accident as a safety measure. The seals of the pump
circulating the MIC through the refrigeration unit were prone to leakages and
after a couple of seal failures, the system was shut down as safety measure.
Had that system been in place and the tank been operated at that temperature,
the reaction would have occurred much slower which would have allowed ample
time to authorities to come up with mitigation plans. Further, according to
some reports, the caustic scrubber in the vent which could have neutralized
some of the MIC was out of service for maintenance. Scrubbers function by
causing a close contact between the liquid and gas streams and the MIC passing
through the vent should have contacted caustic sodium hydroxide which would
have nullified a part of the MIC. Lastly, the flare, which burns the vented
gases going through it and acts as the last line of defense in most chemical
processing plants was also not in service because of corrosion in its header. While it is easy to
argue that given the scale of the disaster, none of these disaster prevention techniques
would have been of any significant help, it is important to consider the fact
that had these systems been in proper operation, it would have helped
significantly in disaster management and rescue efforts by slowing down the
entire exothermic reaction and hence, in turn giving the authorities more time
to rescue and save people.
My future research for this term paper will focus
on analyzing the root causes of the disaster (as mentioned above and even
analyzing other possible factors) in greater detail. I will also provide some
economic background about what the country was going through economically,
politically and socially when it was decided to set up the plant in Bhopal.
According to me, serious lapses by the local authorities played a significant
role in making the disaster relief efforts slower and less effective and I
believe their role also needs to be pointed out.