Carbon Monoxide Headquarters
CO and Risk



Carbon Monoxide Poisoning

Special Groups at Risk:

Coronary Artery Disease:
The study featured below is one of several studies of coronary heart disease and very low CO concentrations that have become classics, and have been extremely important in the setting of CO standards for outside air. They have provided convincing evidence that even very small amounts of CO in the air, and the corresponding COHb levels, result during modest physical exercise in chest pain and electrocardiographic evidence that the heart muscle is receiving insufficient oxygen to pump blood through out the body.


Purpose of Study: To determine whether low doses of CO exacerbate myocardial ischemia during a progressive exercise test.

Method: The effect ...... was evaluated using the objective measure of time to development of electrocardiographic (EKG) changes indicative of ischemia and ......... angina. 63 male subjects (41-75 years) with well-documented coronary artery disease, who had exertional angina .......... ST-segment changes in their electrocardiograms, were studied. .........................

Results: There were 5.1% (p = 0.01) and 12.1% (p less than or equal to 0.0001) decreases in the time to development of ischemic ST-segment changes after exposures producing 2.0 and 3.9% COHb, respectively......... In addition, there were 4.2% (p = 0.027) and 7.1% (p = 0.002) decreases in time to the onset of angina after exposures producing 2.0 and 3.9% COHb, respectively..........

Conclusions: A significant dose-response relationship was found for the individual differences in the time to ST end point and angina for the pre- versus post-exposure exercise tests at the three COHb levels. ........ low doses of CO produce significant effects on cardiac function during exercise in subjects with coronary artery disease.

From: Allred, E.N., Bleecker, E.R., Chaitman, B.R., Daham, T.E., Gottlieb, S.O. (1991) Effects of carbon monoxide on myocardial ischemia. Environ. Health Perspectives, 91, 89-132.


Note: The figure at right is a compilation of data done by EPA from a number of studies on the topic. See the original EPA documents cited elsewhere on this website for details.

...... last changed 06/01/04



Back to CO at Risk Index