Remember Remember the 3rd December: What Happened?

Lily Frost - Writer

This is the first part of a series where I will delve into the Bhopal gas tragedy. Many young people may not have heard of this industrial disaster because it happened before they were alive. Therefore in this first part I will discuss what actually happened in the events that took place on the 2nd/3rd of December 1984.

This year marks 35 years since the Bhopal Disaster; the disaster that was dubbed the 'Hiroshima of the chemical industry’. On the 3rd December 1984, a massive cloud of poisonous gas was released from a Union Carbide pesticide plant in Bhopal, India. It is believed that 42 tonnes of this poisonous gas was exposed to more than 500,000 people. It has been reported that within the first 72 hours after the leak, up to 10,000 people died. Later, 15,000 people died of related diseases. Many years after the event, people are still struggling day to day with chronic and debilitating illnesses as a consequence. Thus, this disaster is by no means over. Today, in Bhopal thousands of innocent people are still suffering from a variety of gas related illnesses including respiratory and psychiatric problems, joint pains, menstrual irregularities, tuberculosis and cancers. However, what followed in second and third generations is even more tragic, an ever escalating arise of birth defects, including cleft palates, webbed feet and hands, twisted limbs, brain damage and heart problems, which left these infants scarred for life as a consequence of the disaster. However, I will be talking in much more detail about how the Bhopal Disaster is still causing devastation today in later articles.

So, firstly, what was this toxic gas that caused so much devastation?

The gas that was released by the tonne from the plant, is called Methyl Isocyanate, CH3NCO, which is abbreviated to MIC. This gas is toxic by inhalation, ingestion and contact. To show how dangerous this gas truly is, Kimmerle G, Eben A conducted a study to show the sheer level of toxicity of the compound. Kimmerle found that, 'at a concentration of 2–4 parts per million (ppm) subject's eyes are irritated, while at 21 ppm, subjects could not tolerate the presence of methyl isocyanate in air’. The American Conference of Government Industrial Hygienists quantified this to a specific threshold, whereby they set that MIC is toxic in quantities as low as 0.4 ppm.

As seen above, each time when referring to measurements of MIC, it is always in relation to the ppm. This refers to the parts-per million. In a scientific context, the parts-per million is a set unit to describe and measure small values of miscellaneous dimensionless quantities, e.g. mole fraction. However, it’s difficult to wrap our heads around something so small, so many people have made videos and articles on how to visualise ppm levels. The best video is a TedEd’s called ‘How to Visualise One Part Per Million’. If you have time, it's worth giving the video a watch! In this short video, it shows that, ‘if you had 11,363 pianos worth of piano keys, one of those keys would be about one parts per million’. Another way to visualise it is ‘one parts per million would be a single granule of sugar, among 273 sugar cubes’. Therefore, if 0.4 ppm is the state regulated level whereby the MIC compound is toxic, that is more than half of a single granule of sugar among 273 sugar cubes.
With this in mind, you can hopefully now appreciate just how devastating the consequences were of 42 tonnes of the gas being released into the air in Bhopal.

So, what events transpired on the night of the 2nd December 1984 that caused this devastation? It was reported in the Bhopal Disaster accident summary, written by Heath and Safety Executive that:

At 23.00 hrs on 2 December, an operator noticed the pressure inside the storage tank to be higher than normal but not outside the working pressure of the tank. At the same time a MIC leak was reported near the vent gas scrubber (VGS). At 00.15hrs a MIC release in the process area was reported. The pressure inside the storage tank was rising rapidly so the operator went outside to the tank. Rumbling sounds were heard from the tank and a screeching noise from the safety valve. Radiated heat could also be felt from the tank. Attempts were made to switch on the VGS but this was not in operational mode.

These reactions that were reported were soon followed by the release of MIC into the air. The immediate effect of this was horrifying. As the compound was released, thousands of innocent Indian people were left blind, severe injuries inflicted to the alveolar walls of their lungs, severe corneal damage and death. Later in the series, I am going to delve into the consequences of this leak to the innocent people and whether justice has been served in terms of compensation and blame. However, first I will note what the failings that led to this devastation. An accident summary was written by Heath and Safety Executive in relation to Union Carbide India Ltd, Bhopal, India (3rd December 1984). This accident summary conducted by HSE identified key failings in technical measures that showed ‘failings’ on behalf of Union Carbide Corporation Ltd (UCC). I will outline the three large contributing factors which were noted as significant in causing the toxic leak.

The Out of Commission Flare System

A gas flare, also known as a flare stack is a gas combustion device, used in industrial plants. The U.S. Environmental Protection Agency reported that in industrial plants, gas flares are primarily used for burning off flammable gas released by pressure relief valves during unplanned over-pressuring of plant equipment. Therefore, gas flares are crucial in maintaining a safe power plant when over-pressuring occurs in an emergency. With this knowledge in mind, to know that UCC as a company,  allowed the flare systems to be out of commission shows a lack of concern regarding safety regulations of the plant. What is yet more terrifying is that UCC had not even recognised that the power plant in Bhopal’s flare systems were out of commission, showing intrinsic failure on their part.

An Unwanted Exothermic Reaction

Before the explosion there was an ingress of water which entered the Methyl Isocyanate tank. The combination of water (H2O) and Methyl Isocyanate (CH3NCO) created an exothermic reaction. This reaction caused a net release of energy, since the kinetic energy of the final state is greater than the kinetic energy of the initial state. This vigorous exothermic reaction caused there to be a build up of pressure and heat from within the tank. In power plants, this can be easily fixed by refrigeration systems which maintain power plants at a core temperature. This leads on to the next failure listed…

The Out of Commission Refrigeration System

The refrigeration system used in the Union Carbide nuclear power plant was set to maintain the core temperature at 0°C. However, this particular refrigeration system was out of commission, which meant that after the exothermic reaction, the plant could not be stabilised by reducing the temperature. As a result, when the temperature rose it created latent heat. Latent heat can be understood as a hidden form of energy which is supplied or extracted to change the state of a substance without changing its temperature. Therefore, the latent heat created in the tank made the liquid changes to a gas, which in its toxic form was inhaled and ingested by tens of thousands of innocent people.

These three failures outlined by HSC, shows how negligent UCC were in maintaining the safety of the general public, by not ensuring that the safety measures were in place. However, the accident summary also mentioned failures of UCC after the actual explosion.

These three aforementioned failures were factors that had a direct contribution to the explosion. Each failure was in one way or another linked with the lack of safety systems being in place or being out of commision. This indicates that either Union Carbide Corporation were unaware of this within their own plant or that there was a basic lack of care that these safety measures were not in place. However, those failures occurred before anyone had any reason to assume the world’s worst industrial disaster was about to take place. Therefore, it may be more fair to judge the actions of UCC after the explosion.

Simply put, the way that Union Carbide Corporation acted after the explosion was an inhumane choice.

In the accident summary, it was reported that ‘No information was available regarding the hazardous nature of Methyl Isocyanate and what medical actions should be taken’. This choice meant that doctors, nurses and medical experts in general had no knowledge whatsoever of what they could do to reduce or reverse the damage done to victims. They had no crucial information that could have saved lives. As a result of Union Carbide Corporations’ choice, hospitals did not even stand a chance at caring for victims who had been exposed to the toxic gas.

I aimed to show readers through this article, the failings of Union Carbide Corporation and how the explosion came to happen. Finally, I hope that through this article and the series that you remember the 3rd December 2019 as the 35th Anniversary of this disaster and most importantly, the 35th year of suffering that victims of the Bhopal Disaster will have endured.


EPA/452/B-02-001, Section 3.0: VOC Controls, Section 3.2: VOC Destruction Controls, Chapter 1: Flares. (A U.S. Environmental Protection Agency report, dated September 2000.)

Kimmerle G, Eben A (1964). "The toxicity of methyl isocyanate and its quantitative determination in the air". Archive for Toxicology.

Accident Summary:


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