Agriculture Reference
In-Depth Information
Table 3.1 Properties of Methyl Isocyanate
Common names
Isocyanic acid, methylester, and methyl carbylamine
Molecular mass
57.1
Properties
Melting point: 45 C; boiling point: 43-45 C.
Is a volatile liquid.
Has a pungent odor.
Reacts violently with water and is highly flammable.
MIC vapor is denser than air and will collect and stay in low areas; the
vapor mixes well with air, and explosives mixtures are formed.
May polymerize due to heating or under the influence of water and
catalysts.
Decomposes on heating and produces toxic gases such as hydrogen
cyanide, nitrogen oxides, and carbon monoxide.
Uses
Used in the production of synthetic rubber, adhesives, pesticides, and
herbicide intermediates; also used for the conversion of aldoximes to
nitriles.
Side effects
MIC is extremely toxic by inhalation, ingestion, and skin absorption.
Inhalation of MIC causes cough, dizziness, shortness of breath, sore
throat, and unconsciousness. It is corrosive to the skin and eyes.
Short-term exposures also lead to death or adverse effects such as
pulmonary edema (respiratory inflammation), bronchitis, bronchial
pneumonia, and reproductive effects. The Occupational Safety and
Health Administration's permissible exposure limit to MIC over a
normal 8-hour workday or a 40-hour workweek is 0.05 mg m 3 .
Source : U.S. Chemical Safety and Hazards Board, http://www.chemsafety.gov/lib/bhopal.0.1.htr; Dictionary of
Organic Chemistry , Vol. 4, 5th ed., Chapman and Hall, London, 1982; T. W Graham, Organic Chemistry , 6th
ed., Wiley, Mississauga, Canada, 1996.
On December 3, 1984, the Bhopal plant operators became concerned that
a storage tank was showing signs of overheating and began to leak. The tank
contained MIC. The leak increased in size rapidly, and within one hour of the
first leakage, it exploded and released approximately 80,000 lb (4
10 4 kg) of
×
MIC into the atmosphere.
Introduction of water to the MIC storage tank resulted in a highly exothermic
reaction generating CO 2 , which would have led to a rapid increase in pressure,
which could have caused the release of 40 metric tons of MIC into the atmo-
sphere. The release led to arguably the worst industrial disaster on record. The
human exposure to MIC was widespread, with a half million people exposed.
Nearly 3000 people died within the first few days after exposure, and 10,000
people were permanently disabled. Ten years after the incident, 12,000 death
claims had been filed, along with 870,000 personal injury claims. However, only
$ 90 million of the Union Carbide settlement agreement had been paid out.
As of 2001, many victims did receive compensation, averaging about $ 600
each, although some claims are still outstanding. The Indian government re-
quired that the plant be operated exclusively by Indian workers, so Union
Carbide agreed to train them, including flying them to a sister plant in West
 
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