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Methyl Isocyanate Exposure and Growth Patterns of Adolescents in Bhopal
To the Editor: More than 200 000 people were exposed to methyl isocyanate (MIC) and other gases following the Union Carbide (UC) Pesticide Plant incident at Bhopal, India, on December 3, 1984; in addition to thousands of deaths from acute exposure, this incident has resulted in chronic health problems.1-3 We measured the effects of exposure to fumes from the incident on the physical growth pattern of adolescents.
Methods
Between May 10 and June 30, 2001, we made anthropometric measurements in exposed adolescents as well as in age- and sex-matched unexposed individuals.
The exposed individuals lived within 1 km northeast of the UC plant at the time of the incident; this area recorded a death rate of more than 3% (150 times the normal rate) within a week of the incident.4 The unexposed individuals lived in localities 15 km southwest or 4 km northwest of the factory; these areas were not affected because of the distance and wind direction. Households for survey were chosen randomly; all identified households except 2 provided written informed consent to participate in the study.
The survey team led by a social worker was from a different town and had no prior knowledge of the health of the adolescents. The team recorded body weight, height, sitting height, mid-arm circumference, head circumference, and triceps skinfold of the adolescents, as well as the height, weight, and socioeconomic status of their parents. Ages were based on birth certificates if available, and otherwise on a "people's calendar" relating to important local events/festivals, horoscopes, parental diaries, and ages of other siblings.
The data were analyzed separately for boys and girls by analysis of covariance with 4 groups (unexposed, postnatal exposure, in utero exposure, and preconception exposure [ie, born after the incident to exposed parents]) and 6 potential covariates: age, mother's height and weight, father's height and weight, and socioeconomic status (per capita monthly income above or below Rs 750 [approximately US $15]). For each outcome variable for each sex, only the covariates that were statistically significant at P<.05 were retained in the final model. All analyses were performed using SAS version 8.2 (SAS Institute Inc, Cary, NC) using multiple regression, with the 3 types of exposure forced into the model. The number of families with 2 boys (n = 6) or 2 girls (n = 14) was too small to permit a rigorous analysis of sibling correlation. Instead, analyses were repeated with only 1 child from each family.
Results
The study included 104 families with 68 girls and 73 boys, with 71 of the adolescents exposed to the gases (mean age, 16.9 [SD, 1.3] years) and 70 unexposed (mean age, 16.7 [SD, 1.4] years). The mean (SD) body weights and heights of exposed and unexposed mothers were similar (48.2 [10.1] vs 49.1 [9.0] kg; 149 [5] vs 151 [5] cm), as were those of exposed and unexposed fathers (54.6 [12.3] vs 53.4 [8.9] kg; 163 [6] vs 162 [6] cm). Table 1 presents the outcome variables for the various combinations of exposure and sex. Data for the few individuals who were exposed in utero (exposed: 3 boys, 3 girls; unexposed: 5 boys, 4 girls) were included in the statistical analysis but are not shown in Table 1Table 1. There was no significant effect of any type of exposure, including in utero exposure, in girls. However, exposure was associated with significant decreases in most anthropometric measures in boys (Table 2). The exposed boys had lower levels of several anthropometric variables, although their triceps skinfold measurements were greater. The exposure effect was most pronounced in boys exposed in utero and least severe in boys born before the incident. The analysis of covariance showed no significant effect of exposure on the growth pattern of girls. Repeating the analyses with only 1 child from each family yielded essentially identical results.
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Table 1. Outcome Variables by Sex, Age, and Exposure to Gases From the Union Carbide Plant Disaster in Bhopal, 1984*
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Table 2. Effect in Boys of Exposure to Gases From the Union Carbide Plant Disaster in Bhopal, 1984
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Comment
We found selective growth retardation in boys, but not in girls, who were either exposed as toddlers to gases from the Bhopal pesticide plant or born to exposed parents. The fact that exposed and unexposed girls were virtually identical in all measures suggests that the exposed and unexposed groups were well-matched and that the association observed in boys is truly a result of exposure and not of other unobserved differences in the demographics. The main chemical that escaped from the plant was MIC, which is readily degraded on contact with water and in the body.1-3 One of the degradation products of MIC is trimethylamine, which has been reported to produce selective growth retardation of male progeny of mice, associated with a decrease in serum testosterone.5 It is possible that similar hormonal effects were produced by MIC, its metabolites, or other substances.
Nishant Ranjan, BA;
Satinath Sarangi, MTech;
V. T. Padmanabhan, MPhil
Sanbhavna Clinic
Bhopal, India
Steve Holleran, BA;
Rajasekhar Ramakrishnan, ScD
Department of Pediatrics
Columbia College of Physicians and Surgeons
New York, NY
Daya R. Varma, MD, PhD
Department of Pharmacology
McGill University
Montreal, Quebec
1. Varma DR, Guest I. The Bhopal accident and methyl isocyanate toxicity. J Toxicol Environ Health. 1993;40:513-528.
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2. Indian Council of Medical Research. Scientific studies on Bhopal gas victims, Part-A. Indian J Med Res. 1987;86(suppl):1-86.
3. Dhara VR, Dhara R. The Union Carbide disaster in Bhopal: a review of health effects. Arch Environ Health. 2002;57:391-404.
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4. Kamat SR, Patel MH, Pradhan PV, et al. Sequential respiratory, psychologic, and immunologic studies in relation to methyl isocyanate exposure over two years with model development. Environ Health Perspect. 1992;97:241-253.
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5. Guest I, Varma DR. Selective growth inhibition of the male progeny of mice treated with trimethylamine during pregnancy. Can J Physiol Pharmacol. 1993;71:185-187.
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Letters Section Editor: Stephen J. Lurie, MD, PhD, Senior Editor.
JAMA. 2003;290:1856-1857.
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