Inhalation
Toxicity Studies on Methyl Isocyanate
The
inhalation exposure chambers at NIOH were upgraded and used
for conducting controlled exposure studies in experimental
animals. For the experimental studies, nearly 500 ml methyl
isocyanate (MIC) was synthesized under strictly controlled
conditions. Acute exposure to different concentrations of MIC
was done in Charles Foster rats of both sexes and a total of
five experiments were carried out. High mortality was observed
following MIC exposures and lethal concentrations were
calculated to be between 2700 to 3000 ppm minute. Primary
toxic effects of MIC were found to be on the respiratory
system as indicated by gross morphological observations, blood
gas analysis, analysis of bronco-alveolar lavage fluid and
lung histopathology. There was evidence of liver injury and
abnormalities in sperm counts and morphology were also
observed. Decrease in muscle ATP and rise in plasma uric acid
levels were also detected and may have been responsible for
muscular fatigue. Fall in RBC- diphosphoglycerate level was
also found and this could have aggravated tissue hypoxia in
MIC exposed animals.
Following exposure, the
animals exhibited severe respiratory distress accompanied by
blood stained nasal discharge. Significant reduction in PO2
and rise in pCO2 was observed. Bronchoalveolar lavage revealed
rise in total protein, sialic acid and appearance of
neutrophils. On histopathological examination marked
inflammatory changes were found in the airway epithelium with
evidence of bronchiolitis obliterans.
 Carcinogenicity studies
Inhalation Toxicity Studies on
Methyl Isocyanine
Reproductive Toxicity
studies in experimental animals
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