Forty years after the Bhopal disaster on December 2-3, 1984, several hundred tonnes of toxic waste still remain around the ill-fated Union Carbide plant. Despite pleas from locals and activists — bolstered over the years by orders from the National Green Tribunal and the Supreme Court — to dispose of the waste, the Madhya Pradesh government has only been able to get rid of a small fraction.
Chemical analyses of soil, air, and water samples collected from the area have revealed the presence of toxic compounds at elevated concentrations. This year, Madhya Pradesh received ₹126 crore from the Union government to incinerate around 340 tonnes of the aboveground material, but others have resisted the plan saying burning the compounds will release poisonous fumes that could lead to further contamination and adverse health effects.
What toxins are associated with the disaster?
Union Carbide India, Ltd. (UCIL) built the Bhopal plant in the late 1960s to manufacture an insecticide called carbaryl using a reaction of methyl isocyanate (MIC) with 1-naphthol. MIC is a highly toxic compound. It reacts with water at high temperatures and its reaction with water also releases heat.
On the night of December 2, 1984, a large quantity of water entered a tank storing MIC at the plant such that the MIC was soon boiling. Facilities at the plant to cool the tank were otherwise diverted, leaving MIC vapours to escape to the environment and spread through the settlements around the plant. MIC doesn’t have a particular smell at concentrations at which other gases may become noticeable but it can irritate the eyes. However, given the hours, most of the people exposed to the gas were asleep.
The Union Carbide Corporation has never officially specified which gases were leaked from the plant, including MIC. This decision also compromised health workers’ ability to respond effectively to the hordes of people who showed up in clinics and hospitals in Bhopal that night and the next day. Some visual cues, including the blood-red colour of the viscera of those who died, also raised concerns that hydrogen cyanide was present in the fumes.
What are the toxins at the plant?
As The Hindu reported on December 2, “a 2010 government-commissioned study showed that … the factory premises also contain about 11 lakh tonnes of contaminated soil, one tonne of mercury, and nearly 150 tonnes of underground dumps” — in addition to the 340 metric tonnes earmarked for incineration.
In 2001, the International Journal of Occupational and Environmental Healthpublished an editorial by Jayshree Chander, then at the School of Medicine at the University of California San Francisco. Here, Dr. Chander cited a report Greenpeace released in 1999 where, based on analyses of samples collected at the site in May that year, Dr. Chander wrote that Greenpeace reported the presence of mercury, chromium, copper, nickel, and lead.
According to her, the report also noted the presence of hexachlorobutadiene, chloroform, carbon tetrachloride, and trichlorobenzene, among other compounds.
Reports from the area have also said the plant was disposing of untreated liquid effluent before the events of 1984.
In 2004, the Supreme Court ordered Madhya Pradesh to supply drinking water from tankers to 14 communities around the plant; by 2013 this exercise had expanded to encompass 22 communities.
In 2017, in response to a plea from an NGO, the court ordered the Indian Institute of Toxicology Research (IITR) to test water samples in 20 more communities. In 2018, the IITR reported higher than permitted concentrations of nitrate and chloride compounds and heavy metals. The court subsequently ordered Madhya Pradesh to expand its water-supply operations to 42 communities overall.
Since then, according to Amnesty International, the same NGO and others have identified persistent organic pollutants in 29 more communities and have described it as evidence of contamination still spreading from the plant.
How toxic are heavy metals?
Chromium, copper, lead, mercury, and nickel are classified as heavy metals because their density is at least 5x that of water. Mercury has been known to damage multiple organs even at low concentrations by accumulating in soft tissue and preventing normal cellular function.
The International Agency for Research on Cancer (IARC) has said there is “sufficient evidence” for arsenic and its compounds being able to cause cancers of the urinary bladder and the lungs; for hexavalent chromium to cause cancers of the lungs; and for nickel and its mixtures to cause cancers of the lungs, nose, nasal cavity, and the paranasal sinuses.
According to a 2002 paper in the journal Pathogens and Disease, “Chromium is an essential nutrient required by the human body to promote the action of insulin for the utilisation of sugars, proteins and fats. … But high doses of chromium and long term exposure can give rise to various cytotoxic and genotoxic reactions that affect the immune system of the body.”
Lead is capable of damaging chlorophyll and disrupting photosynthesis in plants and rendering structural damage to cells and hampering their ability to produce energy in animals. Also, lead from inorganic compounds has been correlated with stomach cancer and to a lesser degree with cancers of the lungs, kidneys, and the brain.
High levels of copper in the body have been known to damage the liver, the kidneys, and the gastrointestinal system.
How are organic compounds harmful?
According to the U.S. Environmental Protection Agency, hexachlorobutadiene is a possible carcinogen in humans. When inhaled, ingested, or brought in contact with skin, this compound can cause the liver to store too much fat (hepatic steatosis), destroy cells in the kidneys involved in producing urine, and inhibit brain activity, among other effects. It is also corrosive.
Chloroform by another name is trichloromethane, and is infamous for its effects on the central nervous system. At a sufficient concentration, it can cause an adult to faint, but at even higher ones it can cause death. The IARC has classified chloroform as “possibly carcinogenic” on the back of limited evidence of cancer-causing potential in humans but more reliable evidence in animals.
In the PubChem database of the U.S. National Institutes of Health, carbon tetrachloride, a.k.a. carbon tet, is classified as an “acute toxin” and a “health hazard”. It is notorious for its ability to damage the liver, including causing cancer. At present, a common way to be exposed to carbon tet is via contaminated groundwater. According to at least one review, ingesting 1 ml of carbon tet can also blur vision, damage nerves, and/or cause heartbeat to become irregular.
Trichlorobenzene can take three chemical forms, or isomers, but all of them are volatile and spread easily through the air, although they have also been found in groundwater and in surface water bodies like lakes. These compounds build up in the body’s fatty tissues and at high concentrations can damage the liver and the kidneys.
Finally, persistent organic pollutants (POPs) refer to organic compounds that don’t break down easily and thus last for many years in the environment once they enter it. According to the Stockholm Convention on POPs, their effects include “cancer, allergies and hypersensitivity, damage to the central and peripheral nervous systems, reproductive disorders, and disruption of the immune system.”
Some POPs have also been associated with developmental disorders and worse outcomes in cancers of the liver, breasts, pancreas, and the prostate.
Note: The toxic effects described in this article are not guaranteed to occur, even at the requisite concentration, because toxicity also depends on the demographic, physiological, and genetic characteristics of the exposed individual.
Published – December 03, 2024 07:00 am IST
