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Two-hour methyl isocyanate inhalation exposure and 91-day recovery: a preliminary description of pathologic changes
Abstract:
The accidental release of methyl isocyanate (MIC) in Bhopal, India, was reportedly responsible for the deaths of more than 2,000 people. To study the pathology of acute inhalation exposure to MIC, the tissues of male and female Fischer 344 rats were evaluated immediately after a single 2-hr exposure to 0, 3, 10, or 30 ppm MIC, and through day 91. Early gross pathologic changes in the 30 ppm-exposed rats included a reddish white encrustation around the mouth and nose, a small thymus, and distension of the gastrointestinal tract with gas. Lungs (middle and median lobes) showed consolidation and hemorrhage and failed to deflate when the chest cavity was opened. Microscopic changes in the upper respiratory tract 3 hr after exposure included marked erosion and separation of olfactory and respiratory epithelia from the basement membrane with accumulation of serofibrinous fluid. On day 1, acute inflammation and fibrinopurulent exudate partially blocked the nasal passages. Epithelial cells had sloughed from the nasopharynx, trachea, bronchi, and major bronchioles, leaving the basement membrane covered with fibrin and exudate. Granulomatous inflammation and intraluminal fibrosis of the airways were observed by day 3, with increased intraluminal fibrosis by day 7. Lower airways became blocked by exfoliated cells, mucous plugs, and/or intraluminal fibrosis.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Acute inhalation of methyl isocyanate (MIC) caused severe respiratory damage in rats, including epithelial erosion and airway obstruction. These findings highlight the potent toxicity of MIC to the respiratory system.
Area of Science:
- Toxicology
- Pathology
- Environmental Health
Background:
- Methyl isocyanate (MIC) is a highly toxic chemical.
- The Bhopal disaster, caused by MIC release, resulted in significant loss of life.
Purpose of the Study:
- To investigate the pathological effects of acute inhalation exposure to methyl isocyanate (MIC).
- To evaluate the dose-dependent and time-course effects of MIC exposure on rat tissues.
Main Methods:
- Male and female Fischer 344 rats were exposed to 0, 3, 10, or 30 ppm MIC for 2 hours.
- Tissues were examined immediately post-exposure and up to day 91.
Main Results:
- Gross findings included encrustations, thymic atrophy, and gastrointestinal distension.
- Microscopic examination revealed severe upper respiratory tract damage, including epithelial erosion and inflammation.
- Airways showed progressive intraluminal fibrosis and blockage by cellular debris and exudate.
Conclusions:
- Acute MIC inhalation causes significant and progressive damage to the respiratory system.
- The study details the pathological progression from acute inflammation to chronic fibrosis in airways following MIC exposure.