The Effect of Carbon Monoxide on Humans

This review critiques the scientific literature reporting the effects of carbon monox­ ide (CO) upon humans, examining those exposure situations that result in blood saturation of carboxyhemoglobin (COHb) below 18%, saturations which generally do not result in signs or symptoms of overt intoxication. A reappraisal of the CO literature is desirable for several reasons: 1. A recently reported national survey disclosed that 45% of the nonsmoking blood donors in 18 sections of the country, each one of which included metropolitan and rural areas, had COHb saturations greater than 1.5%, which indicated that exposure to CO in' excess of that permitted by the quality standards of the Clean Air Act of 1971 was widespread and occurring regularly (1-3). If the air quality standard for CO is judged to be scientifically sound, the decision not to enforce it but to relax the standard because of the national energy crisis could place the health of some citizenry in jeopardy. 2. A series of air quality standards for CO for various civilian populations, indus­ trial operations, and special military groups has been promulgated (Appendix A). In several instances these have been based upon scientific observations currently held to be of questionable validity. 3. The administration of certain drugs has been observed to accelerate the catabol­ ism of hepatic heme, doubling the endogenous CO production (4-6). In certain individuals with compromised cardiovascular systems, such an increase could pose a significant toxic stress. 4. Diseases manifesting increased hemolysis feature elevated COHb saturations that could be toxic to individuals with already compromised cardiovascular systems (7). This literature review itemizes the expected and unexpected source� elf CO, summarizes the basic pathophysiology of the gas, and then scrutinizes the effects of CO on human cognitive performance and cardiovascular system.