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NIOSH Testimony on Methyl Isocyanate by R. A. Lemen, December 12, 1984.
NIOSH 1984 Dec:8 pages
This testimony contains information from NIOSH regarding the toxicity of methyl-isocyanate (624839) (MIC). MIC is used largely as an intermediate in the manufacture of pesticides. In the Industrial Organic Chemicals Industry category (SIC-286) in which the manufacture of isocyanates falls, the incidence of injuries and illnesses has in general been lower than for other chemical and allied products' groups and for all manufacturing. MIC has an median lethal concentration (LC50) of 5 parts per million (ppm) in rats exposed to the vapor for 4 hours; for a 2 hour exposure the LC50 was 21ppm. MIC has the ability to irritate, inflame, and corrode tissues including the eyes and respiratory tract, particularly lung tissue. Humans, if exposed to 2ppm for 1 to 5 minutes, would experience tearing and irritation of the eyes, nose and throat; at 20ppm MIC exposure would cause shortness of breath. Uncomplicated death due to MIC exposure at concentrations higher than 20ppm is characterized by congestive heart failure. The majority of deaths would occur within 1 month of exposure. NIOSH is planning a study of Union Carbide records to determine if the subset of workers exposed to MIC can be identified and then tracked. The only NIOSH criteria document currently available related to MIC addressed the diisocyanates. Because of the respiratory sensitization and irritation effects of the diisocyanates, NIOSH recommended exposure limits similar to the OSHA permissible exposure limit of 0.02ppm for MIC.
NIOSH-Author; NIOSH-Testimony; Lemen-R-A; Chemical-manufacturing-industry; Chemical-industry-workers; Isocyanates; Agricultural-chemicals; Lung-irritants; Respiratory-system-disorders; Cardiovascular-system-disorders;
NTIS Accession No.
Asthma and Chronic Obstructive Pulmonary Disease; Disease and Injury; Respiratory-system-disorders;
NIOSH, 8 pages
Page last reviewed: May 5, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division