Abstract

Sequential Respiratory, Psychologic, and Immunologic Studies in Relation to Methyl Isocyanate Exposure over Two Years with Model Development Of 113 methyl isocyanate (MIC)-exposed subjects studied initially at Bhopal, India, 79, 56, 68, and 87 were followed with clinical, lung function, radiographic, and immunologic tests at 3, 6, 12, 18, and 24 months. Though our cohort consisted of subjects at all ages showing a varied severity of initial illness, fewer females and young subjects were seen. Initially all had eye problems, but dominant symptoms were exertional dyspnoea, cough, chest pain, sputum, and muscle weakness. A large number showed persistent depression mixed with anxiety with disturbances of personality parameters The early radiographic changes were lung oedema, overinflation, enlarged heart, pleural scars, and consolidation. The persistent changes seen were interstitial deposits. Lung functions showed mainly restive changes with small airway obstruction; there was impairment of oxygen exchange. Oxygen exchange improved at 3-6 months, and spirometry improved at 12 months, only to decline later. The expiratory flow rates pertaining to large and medium airway function improved, but those for small airways remained low. There were changes of alveolitis in bronchoalveolar lavage fluid on fibre optic bronchoscopy, and in 11 cases positive MIC-specific antibodies to IgM, IgG, and IgE were demonstrated. On follow up, only 48% of the subjects were clinically stable, while 50% showed fluctuations. Thirty-two percent of the subjects had lung function fluctuations. Detailed sequential behaviour over 24 years was predicted for dyspnoea, forced vital capacity, maximum expiratory flow rate (Q25-475), peak expiratory flow rate, Vo2, and depression score. A model for clinical behaviour explained a total variance of52A% by using the factors of cough, Pco2 and X-ray zones in addition to above five parameters. The behaviour of the railway colony group (1640 patients) revealed a similar pattern of illness. When this observed pattern of changes was transferred to the affected Bhopal city sections (with an equitable age-sex distribution), our model results were again validated. Thus the picture of MIC-induced disease seems similar despite the differences for age-sex and initial severity of illness in our cohort and in the population of Bhopal city as predicted by our model.

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Comments

This is a study of the Railway Colony workers studied in Bombay, not those living in the Bustees who had the highest exposures

2/3/2020