Chemical disasters methyl isocyanate

The worst disaster in the history of the chemical industry occurred in Bhopal, in the state of Madhya Pradesh in central India, on December 3, 1984. A leak of methyl isocyanate (MIC) from a chemical plant, where it was used as an intermediate in the manufacture of the insecticide car-baryl, spread beyond the plant boundary and caused the death by poisoning of more than 2,000 people. The official figure was 2,153, but some unofficial estimates were much higher. In addition, about 200,000 people were injured. Most of the dead and injured were living in a shanty town that had grown up next to the plant. 

The worst chemical disaster in history occurred on December 3, 1984, in Bhopal, India, a city of some 1.6 million people in the state of Madhya Pradesh. On that date in the middle of the night, a tank at the Union Carbide India Ltd. plant leaked between 25 and 40 tons of methyl isocyanate, a volatile colorless liquid, into the atmosphere of Bhopal. This highly toxic gas settled onto the city and its inhabitants in a silent, if odorous, cloud. The results were horrific some 3800 people died and another 2700 experienced total or partial permanent disability. By some estimates, more than 10% of the population of Bhopal—170,000 people—suffered some adverse effect from the methyl isocyanate leak. 

Process intensification drastically increases the safety of chemical processes. It is obvious that smaller is safer. In Table 2 some of the more severe chemical disasters of the past century are listed. The table shows clearly how disastrous consequences may arise from the large inventories when something goes wrong. And of course, one may not claim that process intensification would have prevented all those tragedies. Yet a study done at AIChE showed that methyl isocyanate (MIC),... 

The Bhopal Disaster of 1984 was caused by the accidental release of 40 tonnes of methyl isocyanate (MIC) from a pesticide plant of Union Carbide India, Limited (UCIL) located in the heart of the city of Bhopal, India. A total number of victims is estimated as many as 600,0003. The plant was abandoned and remaining toxic chemicals at the site are still discharging into the environment. 

Methyl isocyanate, which was involved in the disaster in Bhopal, India, in 1984, has the chemical formula CH3NCO. Draw its Lewis diagram, including resonance forms. (Note The N atom is bonded to the two C atoms.)... 

The Wall Street Journal reported that several weeks before the Bhopal disaster, Union Carbide changed procedures at its Institute West VA plant, on which the Bhopal plant design was based, to prevent a similar incident. Rep. Henry Waxman (D. CA.) disclosed that a Union Carbide safety team in September had warned of a potential runaway reaction of methyl isocyanate at Institute and the EPA had reported that there were 28 small leaks of the chemical in 1980 at the facility (Winslow, 1985). 

Certain chemical disasters have prominent places in medical history. In 1976, a chemical reactor explosion in Seveso, Italy, released 2,3,7,8-tetrachlorodibenzo-p-dioxin, which contaminated thousands of acres, killed 100,000 animals, and caused the evacuation of hundreds of people (Melius and Binder 1989). In 1984 in Bhopal, India, a carbamate pesticide plant released 30 tons of methyl isocyanate, causing more than 3,000 deaths and 50,000-300,000 injuries (Melius and Binder 1989). The Three Mile Island and Chernobyl nuclear accidents during the 1980s were the culmination of a string of eight nuclear accidents since 1952 (Melius and Binder 1989). Other chemical disasters severely affected local communities but did not generate widespread attention (De La Paz 1997 Withers 1988). 

PU are compounds formed by reacting the polyol component with an isocyanate compound, typically toluene diisocyanate (TDI) methylene diisocyanate (MDI) or hexamethylene diisocyanate. Polyols are relatively non-toxic (i.e., polyether type polyols are found to be safe, because they are low in oral toxicity with almost no irritation effect to the eyes and skin), however, isocyanates are highly toxic and the product can have a significant toxicity if remnants of isocyanate are in it, which manifests itself mainly as a respiratory (as well as a dermal) hazard. Exposure to the vapour of isocyanates directly may cause irritation for the eyes, respiratory tract and skin. Such an irritation may be too severe to produce bronchitis and pulmonary oedema. As health hazards of isocyanates are considered, one immediately remembers one of the worst industrial disasters of the 20th century, that occurred in Bhopal, India, because of the toxic cloud of methyl isocyanate was released accidentally from the Union Carbide pesticide factory in December 1984. An estimated 3,000 people died immediately with a final of some 20,000, most suffocating from the cloud s toxic chemicals, and some 50,000 were injured, most were residents living near the plant. 

The Bhopal disaster, in terms of loss of life and human injury, is the most serious disaster in the history of the chemical and process industries. It took the form of a runaway polymerization of a highly toxic substance — methyl isocyanate (MIC). This took place not in a reactor, but in a storage tank. 

Usha Yes, you are right, Racheli. Bhopal was the worst chemical disaster ever. It occurred on the night of December 2,1984, in the Indian state Madhya Pradesh in the Union Carbide India Ltd (UCIL) plant that produced the pesticide Sevin from methyl isocyanate (MIC). MIC is extremely toxic to living organisms, causing in humans anything from severe coughing to death by suffocation. 

Other disasters at chemical plants followed in 1976 at Seveso (Italy) there was a dioxin escape which polluted over 4000 acres of farmland, killed 100 000 grazing animals and led to the evacuation of 1000 people. Later (1984) in India a release of 40 tonnes of methyl isocyanate from a batch operation at Bhopal resulted in 40 000 deaths and 100 000 injuries. Incidents such as these would have either been avoided or extensively mitigated had the processes been intensified. In the Flixborough case, a very much smaller vapour cloud would probably have been incapable of developing the shock wave which proved to be so damaging. A continuous intensified version of the Bhopal reactor may still have caused fatalities, had the contents been released, but there would have been very many less than actually CKCurred. 

---