Toxicology of Methyl Isocyanate

Since the 1984 tragedy in Bhopal, India, methyl isocyanate (MIC) has been studied extensively to provide data on its toxicity following short-term exposures to MIC vapor. The purpose of this article is to review the toxicologic studies on MIC which were conducted in laboratories under controlled and objective conditions. Human exposure data are, on occasion, discussed, but only for the purpose of comparing results of selected laboratory animal studies with clinical findings. In addition, results of unpublished MIC studies performed in the 1960s at Mellon Institute are presented to expand the toxicity data files and provide a better understanding of MIC’s mechanism of action. As will become evident, the relatively simple molecule of MIC has a complex mode of toxic action. Furthermore, there is no universal agreement on how MIC reacts with biological systems or, following in vivo exposure, which organ systems are affected and for what length of time.