Cleaning Up Bhopal: the World’s Worst Industrial Disaster

worst was still to come, as the number of casualties kept rising, legal battles and the dodging of responsibility intensified, and the chemical contamination kept seeping into the ground at the crippled plant. Recently there finally seems to be progress in this clean-up with the removal of 337 tons of toxic waste for final disposal, but after four decades of misgivings and neglect, how close is Bhopal really to finally closing the chapter on this horrific disaster?

Chemistry Of A Disaster

The Union Carbide India Limited (UCIL) pesticide plant in Bhopal was built in 1969 to produce the pesticide Sevin (carbaryl) which uses MIC (CH₃NCO) as an intermediate. By the time the plant was operating, there were ways to produce carbaryl without MIC as intermediate, but this was more costly and thus UCIL kept producing the pesticide using the MIC-based process. This is why by the early 1980s MIC was still being produced at the UCIL plant, with multiple on-site MIC storage tanks.

The process used to create the carbaryl at UCIL was quite straightforward, involving the direct reaction of 1-naphtol with MIC:

C₁₀H₇OH + CH₃NCO → C₁₀H₇OC(O)NHCH₃

This is similar to the MIC-free process, which uses the same precursors (phosgene and 1-naphtol) to produce 1-naphthylchloroformate. After this product reacts with methylamine, it too produces carbaryl, but avoids the creation of MIC and the hazards posed by this substance. The counterpoint here is that MIC is easy to manufacture through the reaction of phosgene and monomethylamine, and MIC is highly reactive, ergo easy to use.

Unfortunately this high reactivity adds to the hazards already posed by the chemical itself. It will readily react with just about anything containing an N-H or O-H group in a strongly exothermic reaction. In the case of the UCIL plant, a large amount of water (H₂O) had been accidentally introduced to a MIC storage tank, resulting in a violent exothermic reaction that caused 42 tons of MIC to be released into the atmosphere.

Which brings us to the clean-up of such a disaster.

Everything Is Toxic

Unlike with a nuclear accident where you can use a Geiger counter to be quite certain that you won’t come into contact with any hazardous materials, a disaster site like that at the UCIL plant offers no such comforts. The US (NIOSH) health exposure limits for MIC are set at 0.12 ppm on skin for the IDLH (immediately dangerous to life or health), prescribing supplied-air respirators when entering areas with MIC contamination. The exact mechanism behind MIC’s toxicity isn’t known yet, and there is no known treatment following fatal exposure.

In addition to MIC, the now abandoned UCIL plant and its surroundings have been found to be contaminated with other chemicals that were present at the time of the disaster, along with additional toxic waste that was dumped after the closure of the plant. These contaminants include various heavy metals (lead, mercury), carbaryl, 1-naphtol, chlorinated solvents and much more. Ground water contamination has been established at a few kilometers from the UCIL site, as well as in soil, well water and locally grown vegetables, all of which has led to a quiet human tragedy among the (generally poor) population living in the area.

What complicates matters here is that there’s strong disagreement on the exact scope of the contamination. The contamination of the aquifer and groundwater is often disputed by officials, even as epidemiological studies show the clear health impact on the local population across multiple generations. These impacts include cancer, developmental issues and cognitive impairments. People who moved into the area long after the disaster – lured by the cheap land – found the soil to be heavily contaminated and causing health issues. In an admission of the poisoned ground water, the local government has since put a clean water supply in place, using pipes that carry in clean outside water.

Meanwhile, at the former UCIL site, there are multiple 1970s-era (mostly unlined) solar evaporation pits which were used for storing chemical waste. These pits were never emptied, unlike the storage tanks and vats elsewhere on the terrain. This means that these abandoned pits have to be fully decontaminated somehow to prevent even more of the waste that’s still in them from leaking into the groundwater.

Then there are the hundreds of tons of hazardous waste that have been stored without clean plan on what to do with them. The 337 tons in leak-proof containers that have now been moved for incineration are the first major step after a trial run with a batch of 10 tons in 2015, with the emissions from this incineration deemed to be acceptable. In addition to these thousands more tons have been buried or stored elsewhere on the plant’s site.

An Exclusion Zone That Isn’t

A mostly appropriate response to a toxic spill is exemplified by the 2008 fly ash spill at the Kingston Fossil Plant in Tennessee. After a coal ash pond ruptured and spilled heavy metal-laden fly ash into the adjoining Emory River, 40 homes were destroyed and covering 300 acres (121.4 hectares) in toxic sludge. This was the largest industrial spill in US history.

These fly ash pools used to be unlined pits, not unlike those at the UCIL plant. Those involved in the clean-up suffered a range of health-effects, with dozens dying. The plant owner – TVA – ended up having to purchase the contaminated land, with the clean-up resulting in a partial recovery of the area by 2015 and by 2017 the river was deemed to have ‘recovered’. The home owners in the area did not have to live in the sludge, TVA was on the hook for remediation and payment of compensation.

Remediation mostly involved removing the countless tons of sludge and disposing of it. Current and new fly ash ponds had to be fitted with a liner, or be shut down, along with a string of new safety measures to prevent this type of accident.

In the case of the UCIL plant at Bhopal, the affected area should have been turned into an exclusion zone, and inhabitants relocated, pending environmental assessment of the extent of the contamination. Even in the Soviet Union this was possible after the RBMK core steam explosion near Pripyat, which resulted in today’s Chornobyl Exclusion Zone. Unlike radioactive isotopes, however, heavy metals and toxins do not quietly go away by themselves if left alone.

Considering the sheer scope of the contamination around the former UCIL plant in Bhopal, it does seem realistic that this area will not be suitable for human habitation again within the next hundreds to thousands of years, barring a thus far unimaginable clean-up effort.

Featured image: Deteriorating section of the UCIL plant near Bhopal, India. (Credit: Luca Frediani, Wikimedia)

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