Methyl Isocyanate Exposure

To the Editor: We read with interest the paper by Avashia et al reporting an absence of effects after low exposures to methyl isocyanate(Effects of Prolonged Low Exposure to Methyl Isocyanate. J Occup Environ Med. 1996;38:625-630). Amid controversy over the existence and nature of persistent disease in survivors of the 1984 Bhopal disaster, we welcome continuing research in this area. As the authors imply, however, their findings may have little bearing on the situation in Bhopal, where very large numbers of people (of all ages and both sexes) were exposed for a brief period to very high intensities of methyl isocyanate (MIC). Two points of clarification might be useful. First, we are unclear whether the study by the Avashia et al group included only current employees, and to what extent, therefore, the findings reflected a bias in survival? Second, it would be useful to know whether the (highly subjective) exposure assessments reflected, in any way, short-term intensity("peak") exposures to MIC. Using an assessment based on such "peak" exposures, is there any evidence, among the workforce, of obstructive disease in those who have experienced such exposures (for example, after accidental "spills")? Finally, we would question the omission of the results of small-airways function testing. MIC is highly volatile and probably penetrates deep into the respiratory tree; bronchiolar disease in Bhopal victims is well recognized (Weill H. Disaster at Bhopal: the accident, early findings and respiratory health outlook in those injured. Bull Eur Physiopathologie Respiratoire. 1987;23:587-590; Cullinan P, Acquilla SD, Dhara VP. Long-term morbidity in survivors of the 1984 Bhopal gas leak. Nat Med J India. 1996;9:5-10) but may not be apparent if indices only of large-airway function(as here) are examined. Paul Cullinan, MD Department of Occupational and Environmental Medicine; Imperial College (NHLI); London, UK Dr S. Acquilla Epidemiology & Medical Health; The Medical School; University of Newcastle Upon Tyne; Newcastle, UK