Abstract
Some of the challenges of BGT were answered by two multi-disciplinary
projects of the ICMR on Pathology and Toxicology and Pathophysiology.
Unlike other chemical disasters, the aerosol inhaled by the Bhopal
victims contained a mixture of MIC and its trimers and dimers, as
well as aqueous and thermal decomposition products, including HCN.
A coordinated GC-MS study of the blood and autopsy tissues and chemicals
in the Tank residue confirmed their role. Autopsy studies revealed
the pathological changes in the acute, sub-acute and chronic phases
progressive changes of pulmonary edema and bronchiolitis, followed
by chronic pulmonary fibrosis. Cerebral edema resulted in `acute
histotoxic anoxia'. Intensive experimental studies with the help
of newer tools of molecular biology might throw more light on the
underlying mechanisms and newer therapeutic approaches. The initial
finding of cherry-red discoloration of lungs led to a suspicion of
cyanide toxicity. Eventually, elevated blood and tissue cyanide levels
confirmed the prompt therapeutic response to NaTS and accompanying
increase of urinary NaSCN excretion. However, periodic clinical recurrences
and relapses pointing towards `chronic cyanide toxicity' remained
enigmatic. Specific changes the 2-3 DPG levels and Blood Gases were
explained on the basis of N-carbamoylation of end-terminal valine
residues of Hb. Soon, several other end-terminal alpha-amino groups
of tissue proteins were also found to be N-carbamoylated. Had the
attempts at demonstrate S-carbamoylation of glutathione and other
SH radicals of tissue enzymes like rhodanese succeeded, perhaps the
underlying mechanism of chronic cyanide toxicity due to MIC might
have been resolved. Based on the practical lessons learnt in Bhopal,
an attempt will be made to present the salient pathological and toxicological
findings, followed by a brief outline of the principles of planned
laboratory management for alleviation of human suffering from future
chemical disasters.
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