Abstract

Introduction
A large amount (40 tonnes) of MIC gas leaked from the storage tank of the factory of Union Carbide Co. Ltd., Bhopal, into the atmosphere on the night of 2/3 December 1984, killing a few thousand people and leaving several thousand disabled. In the absence of adequate literature it was difficult to predict and prevent long-term effects of MI.C gas on human beings. In order to assess the extent and nature of lung damage a study was undertaken. This article describes in detail the effects on the respiratory system at the end of three and half months.

Material and methods
The material consisted of two groups [Group I (n = 446) and group It (n = 123)]. The selection of these two groups has been described earlier.[9] Each individual was assessed for his/her lung function. Pulmonary function tests consisted of forced expiratory spirography with the help of a Vitalograph (UK) and peak expiratory flow rates (PEFR) measured with the help of Wright's Mini Peak Flowmeter. After explaining the procedure, each subject was made to blow in the vitalograph and a forced expiratory spirogram was recorded. Each subject repeated the performance thrice and the best graph was selected.[6] From this graph, the forced vital capacity (FVC), forced expiratory volume in one second (FEV1), FEV1/FVC ratio and mid expiratory flow rates (MEFR) were calculated. On the basis of these tests, the pulmonary function disability was classified as restrictive or obstructive in nature. Subjects with FVC of 80% below the predicted values6 were labelled as having restrictive disability, they were further, classified into mild (FVC 60-80% of predicted), moderate (FVC 40-60% of predicted) and severe (FVC< 40% of predicted). Similarly, obstruction was further classified on the basis of FEV1/FVC ratio.[6] In those subjects showed airway obstruction, the tests were repeated after giving a bronchodilator aerosol. Pulmonary function tests could not be done in children below the age of seven years because of lack of cooperation.
Routine chest films were taken in subjects with respiratory symptoms and signs, and in those who had abnormal pulmonary functions. Precaution was taken to maintain the consistency of technique to achieve a good comparative standard. Radiographs were reviewed by three independent observers who looked for certain predetermined findings which were noted in accordance with the earlier study from this institute. The zones affected were noted as per the criteria followed by Tuberculosis Chemotherapy Centre.[13]

Results
Demographic patterns in both the groups have already been discussed earlier.[9]
Clinical features. In Group I, all subjects who were interrogated gave a history of burning of nose and throat and dry cough on the night of 2-3 December immediately after exposure to MIC gas. The symptoms gradually improved with the treatment they received. [Table 1] shows residual symptoms and signs in both the groups at the time of the survey (104-109 days later). In Group I, the cough was dry in 107 (23.8%) and productive in 217. In 202 subjects (45%), the sputum was small in quantity and the patients had a lot of difficulty to bring it out. The chest pain was continuous and dull-aching in nature and used to be aggravated by coughing and deep breathing. In this group, 52 (11.6%) subjects were smoking more than 5-10 bidees/cigarettes per day.
In Group 41, the cough was dry, in 13 and productive in 8 subjects. In this group, 28 (22.8%) subjects were smokers smoking more than 10 cigarettes/bidees per day.
Pulmonary function tests
Group I [Table 2] Pulmonary function tests could be done in only 326 subjects of Group I. Restrictive disability was present in 160. The details regarding severity of restriction and/or obstruction are presented in [Table 2] and [Table 3] which are self-explanatory.
Chest radiography
Chest radiography was done in 306 of Group I and 81 of Group II subjects. The details are given in [Table 4].

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