Biological Effects of Short, High-Level Exposure to Gases: Carbon Monoxide.
Phase rept. May 79-May 80,
ENVIRO CONTROL INC ROCKVILLE MD
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This report presents an analysis and synthesis of the available literature describing health and performance effects of exposure to carbon monoxide CO. The US Armys concern is with high-level, short-term exposures that may exceed present threshold limit values of the American Conference of Governmental Industrial Hygienists 50 ppm as a TWA and a ceiling of 400 ppm for 15 minutes. The organs primarily affected by exposure to CO are the heart and brain, with effects caused by impaired oxygen delivery. During brief exposures to concentrations of up to 35,600 ppm, there was an electrocardiographic change suggestive of myocardial ischemia within 15 seconds after the start of exposure, although there were no changes in heart rate, blood pressure or blood chemistry values in young healthy subjects. The first subjective sign of CO toxicity will probably be a headache followed by a awareness of a pounding heartbeat however, the great variation in tolerance precludes establishment of threshold values per se, although a carboxyhemoglobin COHb of 15 percent would probably not elicit these symptoms in most healthy subjects. Laboratory studies have shown a reduction in work capacity following CO exposure in humans. The basis for this lower work capacity has been investigated in both humans and animal models, which is compensated for by an increase in coronary blood flow in healthy subjects up to 9 COHb in man and 30 COHb in dogs.