Death in a cloud: the Bhopal disaster

Even a brief foray into researching the causes, immediate consequences, and long-term repercussions of the gas disaster at Bhopal in 1984 quickly demonstrates that in order to cover all the aspects of the event fully one would need to write a book, not a blog post. Since other people with access to primary sources have already done this for me, and I refer here to Ingrid Eckerman's fantastic The Bhopal Saga, I will try to avoid doing so, although this is going to be long.

Bhopal is the capital of the Indian state of Madhya Pradesh, located more or less in the middle of the country. It's the second-biggest city in the state, and is--or was--known as the City of Lakes for the multiple natural and man-made lakes in and around the city itself. Union Carbide India Limited (UCIL) had built a chemical manufacturing plant in East Bhopal City in 1969, the same year the ValuJet DC-9 plane was built, which was owned partly by Union Carbide Corporation (UCC) and partly by Indian authorities, although Union Carbide owned all the designs and processes used at the site.


UCIL Bhopal's main product was the insecticide carbaryl. Sold under the trademark Sevin, carbaryl is one of a group of chemicals called carbamates which happen to be cholinesterase inhibitors, meaning that they prevent the enzyme cholinesterase from breaking down the neurotransmitter acetylcholine and therefore do extremely unkind things to the human nervous system; without cholinesterase getting rid of the acetylcholine sitting around in synaptic clefts, the nerves controlling our muscles don't stop firing, causing neuromuscular paralysis and eventual death. So we can see that carbaryl and its relatives aren't necessarily something you want large quantities of in your back yard; however, much like methamphetamine, the process used to make this nasty substance is even more dangerous and poisonous than the substance itself. One particular compound required to make carbaryl at the Bhopal plant is methyl isocyanate, or MIC. MIC killed an unknown number of people, probably between 8,000 and 10,000, in and around Bhopal on the night of December 2-3, 1984--and continues to claim victims today, as survivors of the Bhopal disaster slowly succumb to exposure-related illnesses.


I cannot emphasize enough how absolutely nightmarish the Bhopal plant was--and is to this day--in terms of toxic chemicals. MIC will kill you, but so will chlorine, phosphene, methyl carbamyl chloride, monomethylamine, cyanuric acid, hydrogen chloride, and all the other multisyllabic substances involved in and resulting from the production of carbaryl. Over here in the States when we think of toxic chemicals Woburn and Love Canal and Valley of the Drums and Hinkley come to mind: what happened at Bhopal casts all the chemical accidents in the US far into the shade. Here was not a royal fellowship of death, but a treasure-house of it; an Aladdin's cave of substances inimical to human life and health, all sitting within a hundred yards of the poorest shanties of Bhopal.


In order to make Sevin, you need to combine chlorine and carbon monoxide to form phosgene, then combine that with monomethylamine and chloroform to produce methyl carbamyl chloride (and hydrogen chloride gas). You then break down the methyl carbamyl chloride into methyl isocyanate, which you react with alpha-naphthol and carbon tetrachloride to finally produce carbaryl. There is a separate process by which you can make carbaryl without using MIC, but it costs more, so it wasn't an option.


Now do that on an industrial scale with profit as the priority, with poorly maintained equipment, poorly trained or untrained workers, poorly trained or untrained supervisors ignorant of the physiological effects of the substances they were handling, and set your manufacturing plant within pebble-throwing distance of residential neighborhoods without telling the inhabitants what your process involves or what to do in a chemical-release emergency (other than that you make "medicine" for crops), and you’ve got UCIL’s operation at Bhopal to a T. UCIL did provide Bhopal hospitals with some resuscitation equipment, but provided no emergency procedures for gas-release incidents.


MIC, as a crucial ingredient in the carbaryl manufacturing process, was required in large amounts on the site. When the plant was built, UCIL only manufactured carbamate pesticides from concentrated ingredients shipped in from the US: however, in 1980, UCIL equipped the Bhopal plant with the necessary setup to manufacture it from chlorine (brought in from external suppliers) and carbon monoxide produced on-site. MIC was stored in two of three main tanks, designated 610, 611, and 619; the Union Carbide manual stated that only two of the tanks were to be used for storage at any given time, that the tanks' contents be refrigerated to five degrees centigrade or below and kept under a controlled pressure of nitrogen gas, and that the tanks and fittings should be made out of stainless steel and not any other alloy (including carbon steel).

The tanks were designed with a relief valve vent header (RVVH) which led directly to a vent gas scrubber (VGH) which bubbled the escaping gas through a solution of lye to neutralize it before burning it off from the plant's flare tower or releasing it from the stack. In the event of a tank reaching its pressurization limit (40 pounds per square inch over atmospheric pressure, or psig), a rupture disk would burst, a relief valve would open, and the gas would be released to the vent scrubber. As MIC reacts with water, a nitrogen pressurization system was built in to ensure the dry nitrogen atmosphere inside the tanks wouldn't become contaminated with moisture from the air: if a tank's pressure fell below 2 psig, nitrogen would be pumped into the tank through a connector to a second line running from tank to scrubber, the process vent header (PVH). We have at this point two main routes for gas to escape from any one of the three MIC storage tanks: the RVVH and the PVH.


Piping in the plant was prone to developing clogs due to corrosion or deposited salts from the chemicals running through them, and washing out of the pipes with water was a commonplace task. A barrier, called a slip-bind or slip-blind depending on your source, should have been inserted into the pipes in question to ensure water didn't escape the section being washed out. This very important safety procedure was apparently left out of the written instructions provided to workers for washing out the pipes, according to Eckerman, who cites the Union Research Group of Mumbai (Bombay)'s 1985 report, The role of management practices in the Bhopal gas leak disaster.


In addition to the incomplete procedure instructions, the Bhopal plant lacked a rather damning number of security measures that a similarly purposed US Union Carbide plant considered necessary for operation, contrary to UCC's initial insistence that Bhopal was run to the same standard as its stateside plants. Eckerman offers a table of the security features at UCC's plant in Virginia that were not available/implemented in Bhopal, including:


--Non-MIC carbaryl production process (patented by UCC)


--Storage of MIC only in small quantities, in small vessels, for short times


--Fully-computerized four-stage alarm system


--Monitoring of chemical inventory


--"Knock-down" tank to handle MIC overflows before they could be released


--Emergency VGS with extra capacity


--VGS and flare tower available at all times, not just when MIC was being produced


--Refrigeration with backup refrigeration system to keep MIC at -10 degrees C


--Exclusive stainless steel construction


--Location downwind, outside of town


--Siren/alarm system pointed outward and capable of alerting residents of town


In the initial years of the Bhopal plant's self-sufficient MIC/carbaryl production era, it was run by an American engineer who was committed to safety. In 1982, he was replaced with an Indian engineer educated in the States, directly subordinate to a financial controller most interested in reducing/controlling the company's losses. This is when it started down the garden path to hell, and the first few steps along that path were to screw up staffing/hiring policies for the MIC plant and fire a bunch of employees, as well as cutting down training from 6 months to 8 weeks--which, according to some of the workers, were barely sufficient to give them the necessary skills. When one worker complained about being asked to take on the role of a full-fledged operator after 5 weeks of training, he was apparently allowed to complete the final three.


On the night of the disaster, there were no trained engineers on the site. And this is not making Play-Doh or putting the lids on pies, this is life-and-death stuff they're dealing with.


Eckerman's list of malfunctioning, disconnected, or nonexistent safety systems at Bhopal reads like a disaster movie's build-up stage. Surely no one could have let this go on in real life? Surely all these systems could not be malfunctioning this badly at once? Didn't anyone care?


Probably they did, but it was more than their jobs were worth to complain. The Bhopal plant had been granted a license to produce something like 5,000 tons of pesticide a year. In point of fact they were selling around 2,000. People who knew the Indian market had asked that a smaller plant be built, but this had been bulldozed over by UCC, with the predictable result that Bhopal was run at a loss and the UCIL management was constantly trying to cut costs and raise profits: thus the staffing cuts, thus the replacement of stainless valving and pipes with carbon steel, thus the draining of the MIC refrigeration unit and the use of the system's freon in other plant operations. One after one after one, the systems that should have prevented Bhopal's disaster were deliberately shut down, either to save money or because they just weren't working right.


Unsurprisingly, there had been "warning" accidents in the months leading up to December 84. MIC exposure accidents, leaks of MIC, chlorine, monomethylamine, phosgene, and carbon tetrachloride (sometimes in combination); rather dreadfully, Eckerman mentions that "a journalist...had listened to the workers' discussions about the dangers at the factory--toxic gases, deadly leaks, and the likelihood of explosions. After having done some research, he started to write articles in the local press, warning of the hazards associated with the plant. His final article, which appeared just five months before the disaster, was titled 'Bhopal on the Brink of a Disaster.' No one took any notice. He also sent letters where he summarized the findings of his investigations to the Chief Minister and the Chief Justice of the Supreme Court, and requested them to close down the factory. He got no answer."


Tank 610, which would eventually kill something more than twenty thousand people, was causing problems long before the accident itself. Eckerman writes that on October 21, 1984, less than two months before the disaster, it could not be pressurized; managers switched to tank 611, more biddable, to continue Sevin production. Nobody bothered to find out why 610 misbehaved. On November 30 (or 26, depending on sources) nitro pressure in 611 fell, making them wonder what the hell was wrong with these here tanks in this here plant and causing an investigation that ended with the replacement of a faulty valve on tank 611--and the abandonment of 610. "Operators later told journalists that every time nitrogen was pumped in [to tank 610], it leaked out again through an unknown route."


Let's skip ahead, shall we? Tanks 619, 611 and the recalcitrant 610 are entombed in a concrete mound some distance from the Sevin unit and flare stack. On the night of the accident, the following conditions existed:


1) Tank temperatures were not being logged

2) The vent gas scrubber (VGS) was not in use (this does not entirely fit with some reports of the sodium hydroxide scrubber solution registering a temperature, on the morning after the accident, that indicated a reaction had taken place)

3) The refrigeration system on the MIC tanks was not in use and could not be activated as its refrigerant had been nicked for use elsewhere onsite

4) A slip bind was not used when the pipes were being washed

5) The concentration of chloroform in 610 was too high

6) The tank was not pressurized with nitrogen (or anything else)

7) The tank's high-temp alarm was not functioning

8) The evacuation tank (619) was not empty


There are several major reports covering the incident itself, which most people agree began with water washing of some of the pipelines of the plant. Supervisors on duty at the time were not familiar with the factory's complex maintenance procedures, and knew nothing about MIC or phosgene: in fact the supervisor was convinced that there could not be a leak when production of MIC had been stopped.


The 1988 Arthur D. Little Inc. report, which UCC used to support the sabotage theory, states the following:

"Shortly before the end of the second shift, at 10:20 p.m., the pressure in Tank 610 was reported to be at 2 psig. The shift change occurred at 10:45 p.m., and everything was normal until 11:30 p.m., at which time a small leak was reported downwind and in the area of the MIC production unit. The MIC supervisor said that he would deal with the leak after tea, which began at 12:15 a.m. The tea lasted until 12:40 a.m. at which time all was normal. At that point, the control room operator observed the pressure rise suddenly in Tank 610, and within minutes the indicator was off the gauge's scale. At 12:45 a.m., the safety valve on the tank opened, and gas came out of the stack of the vent gas scrubber. The operators ran to the tank and found it rumbling, and the concrete over the tank was cracking. The fire squad sprayed the stack to knock down the gas, and the reaction subsided an hour or so later. The workers claimed to have no idea as to why the pressure rose in the first instance. According to this account, the incident occurred suddenly and inexplicably."

This is at best disingenuous. Water--a considerable amount of it, thousands of pounds--entered tank 610, and there was evidence of an MIC leak before the main catastrophe that was going to be dealt with "after tea." The boy whose job it was to bring the control room operators their nice tea for their break noted that there was a seriously taut atmosphere and nobody for some reason actually took him up on his tea offer. This was uncharacteristic.

The thing about water and MIC is that they react like eighties movie teenagers and produce a hell of a lot of heat. They produce even more heat in the presence of iron, which would have been present in the contaminant water due to pipe corrosion (carbon steel was used in place of stainless to keep costs down). MIC is such an unstable chemical that it reacts with itself under the right circumstances, and in tank 610, it was gleefully doing so in an exothermic sort of way, creating more heat with every single atom undergoing change, and in a very short time this pressure exceeded the 40 psig tank rupture disk, releasing MIC and a bunch of other chemicals directly to the vent gas scrubber. Which would have meant something, had the VGS a) been working or b) been capable of handling a release of this magnitude.

Times for the various events occurring during the disaster vary. Here's a summary from Eckerman directly off Google Books, which contradicts the timeline Wikipedia presents:

20:30 (8:30 PM): Press in 610 noted as 2 psig. Operator told to wash out lines close to MIC tank(s). Presumably, not provably, operators failed to install slip-binds (due to incomplete instructions) and allowed water to flow freely through the piping of the relief valve vent header and/or the process valve vent header. Various accounts state that operators did not use slip-binds, that they noticed water was not coming out of bleeder lines and shut off the water flow, and that supervisors then ordered them to resume the flow.
22:00 (10:00 PM): Approximate time when water began to enter (presumably unpressurized) tank containing 42 tonnes of MIC minus refrigeration. Reaction begins.
22:30 (10:30 PM): one report states that workers told to use water to continue to clean lines (i.e. keep tap running) and that night shift would turn it off; new operators came on duty, poor bastards, and logged 610's pressure as 2 psi. Alternate reports state that shift change occurred at 10:45 or 11. Some reports mention throat and eye irritation from a MIC leak close to the area where the lines were being washed around 10:45.
23:00 (11:00 PM) One report marks the first report of an MIC leak by a field operator by the VGS; operator said later that the press was 2 psi, but in other reports is mentioned as saying that the 2 psi reading was 3 hours old.
23:30 (11:30 PM) Last transfer of MIC to the Sevin unit. Seems to have come from tank 610 not 611. In addition:
-'The operators on ground level noticed dirty water spilling from a higher level in the MIC structure and MIC in the atmosphere. The MIC and dirty water were coming out of a branch of the RVVH. The pressure safety valve had been removed and the open end of the RVVH branch line was not blinded.'
-'The operators found brownish water and steam coming out from a drain-cock eight yards off the ground. The supervisor recommended turning off the taps after the tea break. The team left for the staff cafeteria.'
The really telling point is 12:15 PM, when the transfer of MIC from tank 611 to the Sevin unit occurred, which UCC investigators concluded to be an attempt by MIC operators to remove water from the tank. We don't know how the water got in there: we just know it did, and while the Arthur D. Little company and UCC continue to maintain it was due to one or more disgruntled operators squirting water into the MIC tank (despite the fact that doing this would most likely kill him or her very horribly) rather than sheer incompetence, there is no conclusive evidence for the sabotage.

All the reports seem to agree that 12:15 is when things started to go very badly wrong. Pressure in tank 610 was rising through 30 psig and off the scale, which pegged at 55; when control room operators and supervisors ran to have a look at it, they found the tank moving, rumbling, cracking the concrete over it with its vibration and heat expansion, and so hot as to flash cooling water off into steam. One report states that the tank stood on end and fell back again, but did not burst. They ran like hell back to the control room and turned on the VGS system, but couldn't verify that it was working.

It was now 12:30, and clouds of lethal gas were spewing from the plant stack and spreading rapidly through Bhopal. Accounts differ on when the siren was sounded, anywhere from 12:15 to 1 AM, but it was shut off shortly thereafter. Attempts were made to knock down the gas release by spraying water at it, but the sprays couldn't reach high enough to make a difference. One worker was killed when he tried to climb the stack assembly and somehow shut off the release; he was almost immediately overcome by the gas and fell off, breaking several bones. By 1:30, workers were running for their lives: people who lived close to the plant were already dying.

Tank 610 continued to pour MIC and a host of other toxins into the night air until it was empty; some reports mention that the safety valve reclosed (as the pressure fell below 40 psig) around 2:30, and the emission stopped. By now 42 tonnes of deadly gas were flowing through Bhopal, blinding and choking people in their beds.

MIC is heavier than air; it hugs the ground, rolling downhill. The weather conditions on the night of the accident were as bad as they could be: a temperature inversion trapped the gases close to the ground, and there wasn't enough wind to blow the cloud away. There's been considerable controversy over the role played by hydrogen cyanide (HCN) in the deaths at Bhopal: MIC breaks down into HCN at high temperatures, and tank 610 may have reached sufficient temperatures to allow this reaction. Cyanide was found in the bodies of some Bhopal victims, and scientists have merrily argued about which of the many gases making up the lethal cloud was responsible for the deaths, which strikes me as missing the point.

The people of Bhopal were awakened by acute pain in their eyes, noses, and throats; coughing uncontrollably, blinded by tears, vomiting, they fled into the streets to escape. People were trampled to death in the rush to evacuate. Mothers lost their babies when they were literally pulled from their arms by the force of people struggling to push through the crowd. Because MIC is so heavy, concentrations of it were worst right over the ground; the shortest people--children--got the heaviest doses. Many of those who did not die at once succumbed at the grossly unprepared hospitals, drowning as pulmonary edema filled their lungs with fluid or suffocating as their devastated bronchi went into intractable spasm. Doctors had no idea what was responsible for the injuries; eye drops and cough medicine were handed out and glucose drips set up. Bodies were everywhere, piled on one another, littering the streets.

Dawn brought with it evidence of the extent of the disaster. Thousands of bodies--of livestock as well as people--lay where they had fallen. Within a few days every tree in Bhopal lost its leaves, and the grass turned yellow: a blight of biblical proportions. Police trucks carried bodies to be dumped in the river; others were stacked into funeral pyres. Official procedure for identifying the dead was left behind in the rush to clear the city of the dead; we don't know how many people died that night, but initial reports listed the death toll at over two thousand. That figure jumped to 8,000 and then to 10,000 as more and more died of their injuries. All in all, UCIL killed more than twenty thousand people with one accident.

In the wake of the disaster, UCC was faced not only with attempting to address the devastating leak that had occurred, but with preventing another leak. Tonnes of MIC still remained in the other holding tanks, and it was determined that the thing to do was to convert this into Sevin as soon as possible. "Operation Faith" was conducted on December 16, but this time rigorous safety measures were in place and the inhabitants--remaining inhabitants--of Bhopal were evacuated prior to the procedure. Bhopal residents had absolutely no trust left for the authorities; everyone who could fled the city with all their belongings.

It is beyond the scope of this write-up to cover the reaction to Bhopal, or the years which followed. Suffice it to say that this must not be forgotten, that the rest of the world must know about it, tell the next generation what happened. Those who died at Bhopal mattered, and the grossly negligent maintenance and staffing of the UCIL plant that killed them also matters. Remembering Bhopal is remembering that accidents like this can happen, and that the corporations responsible for accidents must make preventing such accidents their priority; that profit does not trump human lives, and that decisions made in a boardroom affect the everyday existence of hundreds of thousands on the other side of the world.

And that's what went wrong.


Information in this post was taken from the following sources:

Eckerman, Ingrid (2004). The Bhopal Saga — Causes and Consequences of the World's Largest Industrial Disaster. India: Universities Press. ISBN 81-7371-515-7. Available via Google Books.

Kalelkar AS, Little AD. (1998) Investigation of Large-magnitude incidents: Bhopal as a Case Study..PDF available. London: The Institution of Chemical Engineers Conference on Preventing Major Chemical Accidents (Arthur D. Little Report)

Labunska I, Stephenson A, Brigden K, Stringer R, Santillo D, Johnston P.A. (1999). The Bhopal Legacy. Toxic contaminants at the former Union Carbide factory site,Bhopal, India: 15 years after the Bhopal accident. PDF available. Greenpeace Research Laboratories, Department of Biological Sciences, University of Exeter, Exeter UK

Stringer R, Labunska I, Brigden K, Santillo D. (2002). "Chemical Stockpiles at Union Carbide India Limited in Bhopal: An investigation". Greenpeace Research Laboratories. PDF available.