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Health Effects

Bhopal survivor with severe eye damage
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Toxicity of Methyl Icocyanate

Prior to the gas leak in Bhopal, there was only one known study on the toxicity of methyl icocyanate (MIC), by Kimmerle & Eben (1964). In 1963 and 1970 the Union Carbide Corporation commissioned animal studies, but did not publish any conclusions. However, after the gas leak much was learned about the toxicity of MIC.


The U.S. Occupational Safety and Health Administration (OSHA), has set workplace standards for MIC at 0.02ppm. The estimated mean MIC concentration in the cloud was 27 ppm, which is 1400 times the OSHA standard. The range of the MIC concentration in the cloud was 0.12-85.6ppm. With people exposed to such a high concentration of MIC there were many acute and long-term health effects.

Acute Effects

Immediate effects of the MIC leak included: burning, redness and watering of the eyes, coughing, difficulty breathing, corneal damage, redness of the skin, vomiting, unconsciousness, fatigue and death. The majority of all deaths within the first four days of the leak were caused by pulmonary edema, or fluid build-up in the lungs.

Long-Term Eye Effects

Early studies conducted 8-60 days after exposure to MIC revealed that those affected by the gas leak reported severe eye burning, watering, pain, redness, sensitivity to light and eyelid swelling. Follow-up studies 9 months to 2 years later reported that eye problems including persistent eye watering, burning, itching, redness, conjunctivitis, and deficiency of tear secretion were still present among those affected by the leak. Andersson et al (1990), conducted a follow-up study of 93% of previously surveyed exposed and control Bhopal residents 3 years after exposure. The results revealed an increased risk of eye infections, watering, irritation and excess cataracts among those exposed.

Long-Term Respiratory Effects

Follow up studies 2-3 months after the accident were conducted on 1, 279 exposed men, women and children. Of 903 subjects who had x-rays, 164 were abnormal. Of 783 subjects who had spirometry, 39% had some form of respiratory impairment. Kamat et al (1987) studied 113 exposed patients at 3 months, 6 months and 2 years after exposure. Symptoms included cough, sputum, chest pain and dyspnea (shortness of breath). These symptoms improved during first year but intensified during second year. Pulmonary function also declined progressively during the two year period of observation. Cullinan et al (1997) surveyed 454 adults for respiratory symptoms and pulmonary function 10 years after the accident. Among those who lived closest to the plant, there was still an increased prevalence of cough and dyspnea and decreased lung function.

Reproductive Effects

Kanhere et al (1987) conducted a large study on pregnancy outcomes in Bhopal after the gas leak and identified 2,566 cases who were pregnant at the time of exposure and 1,218 controls from an unaffected area. The age standardized miscarriage rate was 23.6 % in the affected area versus 5.6% in the control area. Neonatal mortality rates were also higher in the affected area at 60.9% compared to 11.8% in the control area. Exposed women also reported menstrual cycle disruption and dysmenorrhea, or severe uterine pain during menstruation.

Psychological Effects

Psychological problems of Bhopal survivors fell into 4 categories: post traumatic stress disorder, pathological grief reactions, emotional reactions to physical problems, and exacerbation of pre-existing psychiatric problems. One year after the leak, a study by the Indian Council for Medical Research (ICMR) revealed that mental health problems were as high as 132.9 per 1,000 people in affected areas compared to 24.85 per 1,000 people in unaffected areas. In 1990 the rate in the affected areas was still three times higher than unaffected areas.

Effects on Children

The health effects of the gas leak were similar in children compared to those in adults. Studies have shown there is a higher incidence of psychiatric illness, acute respiratory infections, and infections of skin, eyes and ears reported among children from the affected gas leak area compared to control groups. There have been some reports of intellectual impairment in the children affected by the gas leak and also some reports of higher incidence of cleft lip. Also, Ranjan et al (2003) found that boys born to parents exposed to the gas are significantly shorter than unexposed cohorts.

Other Long-Term Health Effects

There have been several animal studies and human studies regarding the effect of MIC on the immune system, but there have been no definitive conclusions. Also, a population based cancer registry was established in Bhopal in 1986. The onset of the gas leak related cancers were not expected to occur before a thirty to forty year lag period. Although, in 2003 it was stated that cancers of the lung increased up to 20% in Bhopal compared to other cities in India.


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