Bhopal accident methyl isocyanate toxicity

Varma DR, Guest I The Bhopal accident and methyl isocyanate toxicity. J Toxicol Environ Health 40 513-529, 1993... 

Varma, D.R., Mulay, S. (2006). The Bhopal accident and methyl isocyanate toxicity. In Toxicology of Organophosphate and Carbamate Compounds (R.C. Gupta, ed.), pp. 79-88. Elsevier, San Diego. 

CHAPTER 7 The Bhopal Accident and Methyl Isocyanate Toxicity... 

The paucity of data on MIC at the time of the Bhopal accident and extensive toxicity data on diisocyanates (Anonymous, 1966 Varma, 1986) prompted the prestigious journal Lancet (Anonymous, 1984a) to comment, In a year s time wc will have learned a lot more about methyl isocyanate — at an appalling price. Indeed, wc did learn a lot in a few years time. The U.S. National Toxicology... 

Varma, D., Guest, I., 1993. The Bhopal accident and methyl isocyanate toxicity J. Toxicol. Environ. Health 40, 513-529. 

There are three types of TAP emissions continuous, intermittent, and accidental. Both routine emissions associated with a batch process or a continuous process that is operated only occasionally can be intermittent sources. A dramatic example of an accidental emission was the release of methyl isocyanate [624-83-9] in Bhopal, India. As a result of this accident, the U.S. Congress created Tide III, a free-standing statute included in the Superfund Amendments and Reauthorization Act (SARA) of 1986. Title III provides a mechanism by which the pubHc can be informed of the existence, quantities, and releases of toxic substances, and requires the states to develop plans to respond to accidental releases of these substances. Eurther, it requires anyone releasing specific toxic chemicals above a certain threshold amount to aimuaHy submit a toxic chemical release form to EPA. At present, there are 308 specific chemicals subject to Title III regulation (37). 

Naphthol is mainly used in the manufacture of the insecticide carbaryl (59), l-naphthyl A/-methyicarbamate/ iJ-2j5 - (Sevin) (22), which is produced by the reaction of 1-naphthol with methyl isocyanate. Methyl isocyanate is usually prepared by treating methylamine with phosgene. Methyl isocyanate is a very toxic Hquid, boiling at 38°C, and should not be stored for long periods of time (Bhopal accident, India). India has developed a process for the preparation of aryl esters of A/-alkyl carbamic acids. Thus l-naphthyl methylcarbamate is prepared by refluxing 1-naphthol with ethyl methylcarbamate and POCl in toluene (60). In 1992, carbaryl production totaled > 11.4 x 10 t(35). Rhc ne-Poulenc, at its Institute, W. Va., facihty is the only carbaryl producer in United States. 

The study of the accidents in chemical facilities, during transportation, storage and others, the research of the chemical products, which are produced and stored, are important points in the preparation of the defence against chemical terrorism. An example of such an accident is the explosion at the Union Carbide pesticide manufacturing plant (Dec. 3, 1984), which scattered toxic methyl isocyanate (MIC) over the city of Bhopal, India. During the first few days up to 4000 people died of painful, harrowing deaths [10],... 

On December 3, 1984, a toxic gas release from a pesticide plant in India killed nearly 3000 people and injured at least 100,000 others. The chemical that leaked was methyl isocyanate, a chemical intermediate that was supposed to be stored in a cooled bunker near the plant s outer boundary. The vapor is highly toxic and causes cellular asphyxiation and rapid death. Despite engineering and procedural provisions to prevent its release, a total system breakdown resulted in the release of 40 tons of the deadly material into the densely populated community of Bhopal. Because of this incident, the plant was dismantled and ultimately the parent corporation. Union Carbide, was forced to make a number of organizational changes. The occurrence is considered by many to have been the most tragic chemical accident in history. 

Methyl isocyanate is a very dangerous chemical. It was responsible for the deaths of over 2,500 people, perhaps as many as 10,000 people, in the worst industrial accident ever, that of the carbamate insecticide plant in Bhopal, India on December 3, 1984. It is a very toxic chemical. This tragedy is discussed in more detail in Chapter 25. Methyl isocyanate can be made from phosgene and methylamine, which would circumvent use of the isocyanate. Phosgene is made from chlorine and carbon monoxide, but it is also very toxic and dangerous. 

Methyl isocyanate was the toxic agent involved in the most catastrophic industrial accident of all time, which took place in Bhopal, India, on December 2, 1984. This accident occurred when water got into a tank of methyl isocyanate, causing an exothermic reaction that built up pressure and ruptured a safety valve. This resulted in the release to the atmosphere of 30 to 40 tons of the compound over an approximately 3-h period. Subsequent exposure of people resulted in approximately 3,500 deaths and almost 100,000 injuries. 

One of the worst industrial accidents occurred in Bhopal, India, on December 2 and 3, 1984. It was due to the leakage of methyl isocyanate (MIC) released from the Union Carbide pesticide manufacturing plant. More than 3,000 people who resided in areas adjacent to the manufacturing plant died within a few hours after exposure to MIC. Death was attributed to severe pulmonary toxicity, followed by... 

On December 3 and 4, 1985, a chemical release causing a massive toxic gas cloud occurred at the Union Carbide India, Ltd, plant in Bhopal, India. (Union Carbide is now a part of The Dow Chemical Company.) The process involved used methyl isocyanate (MIC), an extremely toxic chemical, to make Sevin, a pesticide. According to various authoritative reports, about 1,700-2,700 (possibly more) people were killed, 50,000 people were affected seriously, and 1,000,000 people were affected in some way. The final settlement may involve billions of dollars. It was one of the worst industrial accidents in history. The accident occurred when about 120-240 gallons of water were allowed to contaminate an MIC storage tank. The MIC hydrolyzed, causing heat and pressure, which in turn caused the tank rupture disk to burst. 

Methyl isocyanate (MIC) is the smallest member of the isocyanate family and the most reactive and toxic of all. MIC was almost unheard of until the fateful night December 3, 1984, when nearly 30 metric tons of this poisonous chemical spewed out of the Union Carbide India Ltd (UCIL) pesticide plant within a period of 45-60 min (Jayaraman, 1984). Bhopal turned into a city of death , wrote the fortnightly India Today (December 30, 1984). The journal Nature (Opinion, 1984) vented its anger thus ... the anguish vividly carried round the world by the television cameras seems not to have matured into the anger, even hysteria, there would have been had the [Bhopal] accident occurred on the edge of a European city - or in Connecticut (the headquarters of Union Carbide was in Danbury, Connecticut, USA). 

Although toxic releases, in general, are not the principal cause of major accidents (relative to fire and explosion) associated with the chemical industry, they are a just cause of "considerable public apprehension" [1327a]. This concern has been compounded by an event which occurred in Bhopal, India in December 1984, in which over 2500 people were killed by a single toxic release of methyl isocyanate. 

Even under the best of circumstances in which all possible exposure modes are controlled, it would be foolhardy to make a conclusion of zero exposure. Numerous industrial chemical accidents have occurred. One particularly catastrophic incident occurred in Bhopal, India, in 1984 in which the extremely toxic gas methyl isocyanate leaked out of a closed and contained system resulting in the deaths of perhaps tens of thousands of people. The Bhopal incident dramatically demonstrates that zero exposure (and therefore zero risk) can never be concluded, but it is also possible to go too far in the direction of concluding that all toxic chemicals must be banned for all applications, which is sometimes referred to as the precautionary principle . This important nuance is discussed later in this chapter. 

On December 3, 1984, Bhopal, India, experienced a release of approximately 40 metric tons of methyl isocyanate (MIC) at the Union Carbide pesticide plant. Over 100,000 were injured and 3000 people were killed, and many more are likely to die from the long-term effects. The accident occurred around 12 40 a.m. local time, when most of the victims were sleeping. The dead included large numbers of infants, children, and older men and women. These age groups are often adversely impacted by toxic exposures. 

The world s worst industrial disaster occurred in Bhopal, India, in 1984 in which nearly 40 metric tons of methyl isocyanate was released from a pesticide plant killing over 3000 people. Most deaths resulted from pulmonary edema within 3 days of accident. Many follow-up studies indicated pulmonary, ophthalmic, neurological, reproductive, immunologic and hematologic toxic effects among the survivors. 

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