The Butcher Gas

This time we are going to understand more about the methyl isocyanate,

the gas which is ill known to be associated with Bhopal gas tragedy. There is

abundant data in the media about political aspects, administrative shortcomings

& corporate negligence which led to the unfortunate massacre. I intend to draw

your attention to the scientific details of the very gas, Methyl Isocyanate or MIC.

MICMethyl

isocyanate (MIC) is an organic compound with the molecular

formula C2H3NO, arranged as H3CN=

C=O. Synonyms are isocyanatomethane,

methyl carbylamine, and MIC. Methyl isocyanate is an intermediate chemical in

the production of carbamate pesticides (such as carbaryl, carbofuran, methomyl,

and aldicarb). It has also been used in the production of rubbers and adhesives.

As a highly toxic and irritating material, it is hazardous to human health, and wasinvolved in the Bhopal disaster which killed nearly 8,000 people initially and


approximately 17,000 people in total.

Sources and Potential Exposure

· No information is available on the levels of methyl isocyanate is ambient

air or water.

· Occupational exposure to methyl isocyanate may occur for those workers

who use insecticides and herbicides produced from methyl isocyanate.

Few known exposures to the general public have occurred.

· Methyl isocyanate has been detected in cigarette smoke.

Health Hazard Information

Acute Effects :

· In 1984, in Bhopal, Union Carbide gas leak of methyl isocyanate resulted

in the deaths of more than 2,000 people and adverse health effects in

greater than 170,000 survivors. Pulmonary edema was the cause of deathin most cases, with many deaths resulting from secondary respiratory


infections such as bronchitis and bronchial pneumonia.

· Other effects noted from acute inhalation exposure to methyl isocyanate in

humans are respiratory tract irritation, difficulty breathing, blindness,

nausea, gastritis, sweating, fever, chills, and liver and kidney damage.

Survivors continue to exhibit damage to the lungs (e.g., bronchoalveolar

lesions and decreased lung function) and the eyes (e.g., loss of vision,

loss of visual acuity, and cataracts).

· Animal studies have reported pulmonary edema, upper respiratory tract

irritation, respiratory lesions, and weight loss from acute inhalation

exposure to methyl isocyanate.

· Acute animal tests in rats have shown methyl isocyanate to have extreme

acute toxicity from inhalation exposure and high acute toxicity from oral

exposure.

Chronic Effects (Noncancer):· CalEPA has calculated a chronic inhalation reference exposure level of


0.001 milligrams per cubic meter (mg/m3) based on lung and body weight

effects in rats. The CalEPA reference exposure level is a concentration at

or below which adverse health effects are not likely to occur. It is not a

direct estimator of risk but rather a reference point to gauge the potential

effects. At lifetime exposures increasingly greater than the reference

exposure level, the potential for adverse health effects increases.

· Methyl isocyanate (MIC) is extremely toxic. The threshold limit value set by

the American Conference on Government Industrial Hygienist was 0.02

ppm (the threshold value indicates exposure to the particular substance in

question should not excedd that value. Otherwise it becomes a cause for

problematic health hazards)

· MIC can damage by inhalation, ingestion and contact in quantities as low

as 0.4 ppm. Damage includes coughing, chest pain, dyspnea, asthma,

irritation of the eyes, nose and throat as well as skin damage. Higher

levels of exposure, over 21 ppm, can result in pulmonary or lung edema,

emphysema and hemorrhages, bronchial pneumonia and death.· Although the odor of methyl isocyanate cannot be detected at 5 ppm by


most people, its potent lachrymal properties provide an excellent warning

of its presence (at a concentration of 2–4 parts per million (ppm) subject's

eyes are irritated, while at 21 ppm subjects could not tolerate the presence

of methyl isocyanate in air).

· Proper care must be taken to store methyl isocyanate because of its ease

of exothermically polymerizing and its similar sensitivity to water. Only

stainless steel or glass containers may be safely used; the MIC must be

stored at temperatures below 40 °C (104 °F) and preferably at 4 °C (39 °

F).

· The toxic effect of the compound was apparent in the Bhopal disaster,

when around 42,000 kilograms (93,000 lb) of methyl isocyanate and other

gases were released from the underground reservoirs of Union Carbide

India Limited (UCIL) factory, over a populated area on December 3, 1984,

immediately killing thousands and leading to the deaths of tens of

thousands in subsequent weeks and months.

Reproductive/Developmental Effects:· After the Bhopal, India, accident, an unusually high percentage of


survivors had disorders of the reproductive system, including leukorrhea,

pelvic inflammatory disease, excessive menstrual bleeding, and

suppression of lactation.

· Other adverse effects included increases in the number of stillbirths,

spontaneous abortions, and increased infant mortality.

· Animal studies have reported increased incidence of fetal deaths and

decreased fertility, live litter size, fetal body weight, and neonatal survival

following inhalation exposure to methyl isocyanate during pregnancy.

Cancer Risk:

· In a study in which animals were exposed once by inhalation, no tumors

were significantly associated with methyl isocyanate exposure in mice and

female rats; male rats had marginally increased rates of tumors of the

pancreas.· EPA has classified methyl isocyanate as a Group D, not classifiable as to


human carcinogenicity. Although, it is not clear if MIC is one of the

triggering agents that cause cancer.

Looking ForwardAfter

24 years it has clearly become a judicial tragedy (with all due respect

to Judicial System) which hurts more than a gas tragedy since it attacks our

collective consciousness. It becomes very important that we ensure installation

of all safety & security measures in the potent threatening establishments.

Whether we like it or not, primary focus should be given on installation &

constant upkeep of security mechanisms, training of employees than on having

maximum foreign direct investment. FDI/ FII is welcome but not at the cost of

indigenous lives. We got to have it clear that while passing Nuclear Liability Bill,

we fix the responsibility on defaulters. I can see a ray of hope in the way

government wants to review the Bill.

Next time we will read about what US media calls as Obama’s 9/11 that is

Mexico gulf oil spill. Do write to me in the mean time. You can read some of my

previous articles on my blog