Biological Effects of Short-Term, High-Concentration Exposure to Methyl Isocyanate. I. Study Objectives and Inhalation Exposure Design

Early reports from India indicated that humans were dying within minutes to a few hours from exposure to methyl isocyanate (MIC). Attempts to explain the cause(s) of these rapid mortalities is where Union Carbide Corporation concentrated its post-Bhopal toxicologic investigations. The MIC studies in...

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Bibliographic Details
Published in:Environmental health perspectives 1987-06, Vol.72, p.13-19
Main Authors: Dodd, Darol E., Frank, Fred R., Fowler, Edward H., Troup, Catherine M., Milton, Robert M.
Format: Article
Language:English
Subjects:
Animals
Carbides
Chemical hazards
Cholinesterase Inhibitors
Cyanates - administration & dosage
Cyanates - toxicity
Death
Female
Guinea Pigs
Humans
Inhalation
Isocyanates
Lethal Dose 50
Lung - drug effects
Male
Mortality
Rats
Rats, Inbred Strains
The Toxicity of Methyl Isocyanate. March 12-13, 1986. Research Triangle Park, NC
Time Factors
Vapors
Volatilization
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Summary:Early reports from India indicated that humans were dying within minutes to a few hours from exposure to methyl isocyanate (MIC). Attempts to explain the cause(s) of these rapid mortalities is where Union Carbide Corporation concentrated its post-Bhopal toxicologic investigations. The MIC studies involving rats and guinea pigs focused primarily on the consequences of acute pulmonary damage. All MIC inhalation exposures were acute, of short duration (mainly 15 min), and high in concentration (ranging from 25-3506 ppm). MIC vapors were statically generated in a double chamber exposure design. Precautionary measures taken during exposures are discussed. Guinea pigs were more susceptible than rats to MIC exposure-related early mortality. A greater than one order of magnitude difference was observed between an MIC concentration that caused no early mortality in rats (3506 ppm) and an MIC concentration that caused partial (6%) early mortality in guinea pigs (225 ppm) for exposures of 10 to 15 min duration. For both species, the most noteworthy clinical signs during exposure were lacrimation, blepharospasm, and mouth breathing. Fifteen minute LC50tests with 14-day postexposure follow-up were conducted, and the LC50(95% confidence limit) values were 171 (114-256) ppm for rats and 112 (61-204) ppm for guinea pigs. Target exposure concentrations for the toxicologic investigations of MIC-induced early mortality were established. A short summary of pertinent results of Union Carbide Corporation's post-Bhopal toxicologic investigations is presented.
ISSN:0091-6765
1552-9924
DOI:10.1289/ehp.877213