TheBhopal gas tragedy, which occurred on the midnight of 3rd December1984 in the Indian city of Bhopal, is considered as the world’s worstindustrial disaster. According to the World History Project, thirty-two tons ofpoisonous methyl isocyanate (MIC) gas leaked from the MIC storage tank of theUnion Carbide India Ltd. pesticide plant.
Over 500,000 people living in thenearby towns were exposed to the lethal Methyl Isocyanate gas and according toa report by researcher Ingrid Eckerman, over 8,000 people lost their livesduring the initial weeks. The cause of the disaster is still a topic of debatewith the Indian government alleging that slack management combined with shoddymaintenance caused the gas leak while Union Carbide in its defense has claimedthat the disaster was an act of sabotage by vested interests. The plant was built in 1969 bythe Indian subsidiary of the multinational company Union Carbide Corporation(UCC) which is headquartered in TX, USA.
Before the incident, the plant wasused to manufacture a different pesticide called ‘Sevin’. Even before thefateful gas leak, the plant has had a history of accidents in which multipleemployees had either suffered severe injuries or had died. For example, inJanuary 1982, a phosgene leak exposed 24 workers, all of whom had to beadmitted to a nearby hospital. Subsequent findings revealed that workers hadnot been ordered to wear protective masks. A month later, a MIC leak affected18 more workers.
Chemicals abandoned at theplant continue to pollute the environment and ground water resources in thenearby areas. In 2004, 20 years after the tragedy took place, a BBC Radio 5broadcast reported the site to be contaminated with toxic chemicals. It furtherstated that water samples collected from nearby were contaminated by more than500 times the maximum limits recommended by the World Health Organization. The Bhopal tragedy has taughtall of us a very big lesson in risk management. I believe that had there beenproper safety protocols and risk mitigation strategies in place, a disaster ofthis magnitude could have been avoided, or at least curtailed. For thisresearch review paper, the author will limit the scope to analyzing the rootcause of the Initiating Event of the gas leak along with the kind of lapses onpart of the plant management and local civic authorities and the consequencesof their actions.
The fact that even after more than three decades there is noconclusive theory on what caused the gas leak, it is important to analyze allthe different versions that are presented by established researchers. METHYL ISOCYANATEThe UCIL facility in Bhopal, India wasa manufacturing site for carbamate pesticides that had similar design andtechnical specifications to the one in West Virginia. MIC was used as a rawmaterial for these pesticides and the plant stored a large quantity of MIC onsite. MIC by itself is a very volatile liquid with a pungent odor. It is highlyflammable and potentially explosive when reacts with air. With water, it formsan 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 thanthat 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 preventself-polymerization.Descriptionof the PlantFig. 1illustrates the pesticide production facilities at which the MIC was producedin the production plant and consumed on site as a raw material in the pesticideplant (MIC consumer). The plant designrequired MIC storage to be kept at minimum volumes.
A caustic scrubber wasprovided to neutralize any MIC emissions from the storage tanks and a flare waspresent to burn vented MIC. A refrigeration system was also in place to keepthe stored MIC cold & decrease its reaction rate with water.Gas Leak Initiating Event: OperatorError or Sabotage?Any accident begins with an initiating event. Thesame 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 withwater and generates an exothermic reaction, which generates a large amount ofheat as by-product. As the reaction of water and MIC took place, the tank’stemperature and pressure started increasing, slowly at the beginning and thenaccelerated quickly until the venting began.The cause of the disaster (Initiating Event) isstill a debate with different sides arguing differently. One of the theoriesplaces the blame on negligence of plant operators by arguing that in anotherpart of the plant, they did not properly isolate the header while water washingthe vent header which allowed water to reach the MIC tank and react with it. Asecond theory looks at the angle of sabotage from one of the many disgruntledworkers in the plant. The plant was running in losses and there had been aconsiderable of staff reductions leading up to the accident. There waswidespread mistrust between workers and the management and its highly possiblethat one of the workers intentionally injected water into the tank, probably toruin that batch of MIC and not knowing of the larger consequences (D’Silva2006; Kalelkar 1988). A third theory blames the plant management forbypassing key safeguards and preventive measures that act as standard safetyprotocol measures.
For example, the most basic safeguard measure dictates thatthe quantity of MIC stored should be minimal and according to standardoperating procedures, two out of the three tanks should have been empty and thethird 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 thedisaster. Moreover, there was also smaller amounts of MIC present in one of theother tanks. Such high amounts of MIC present in the storage tanks limited theplant management’s options to restrict the exothermic reaction at the time ofthe gas leak. Secondly, a refrigeration system which was present to keep theMIC at 30°F (well below its boiling point) had been turned off justmonths before the accident as a safety measure. The seals of the pumpcirculating the MIC through the refrigeration unit were prone to leakages andafter 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 ampletime to authorities to come up with mitigation plans.
Further, according tosome reports, the caustic scrubber in the vent which could have neutralizedsome of the MIC was out of service for maintenance. Scrubbers function bycausing a close contact between the liquid and gas streams and the MIC passingthrough the vent should have contacted caustic sodium hydroxide which wouldhave nullified a part of the MIC. Lastly, the flare, which burns the ventedgases going through it and acts as the last line of defense in most chemicalprocessing plants was also not in service because of corrosion in its header. While it is easy toargue that given the scale of the disaster, none of these disaster prevention techniqueswould have been of any significant help, it is important to consider the factthat had these systems been in proper operation, it would have helpedsignificantly in disaster management and rescue efforts by slowing down theentire exothermic reaction and hence, in turn giving the authorities more timeto rescue and save people.My future research for this term paper will focuson analyzing the root causes of the disaster (as mentioned above and evenanalyzing other possible factors) in greater detail.
I will also provide someeconomic 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 significantrole in making the disaster relief efforts slower and less effective and Ibelieve their role also needs to be pointed out.