Monoxide heart risk.

Monoxide heart risk

Atmospheric carbon monoxide levels currently deemed acceptable by federal clean-air standards can speed the onset of chest pain in patients with coronary artery disease, new research indicates. The finding suggests that a significant proportion of the more than 6 million Americans with coronary disease run a risk of myocardial ischemia -- a potentially damaging lack of oxygen in heart muscle -- when exposed to even low levels of the gas in the workplace or after spending as little as one hour in traffic-congested areas.

Carbon monoxide, a colorless, odorless by-product of incomplete fuel combustion, inhibits the release of oxygen from red blook cells to body tissues. Bernard R. Chaitman of the St. Louis University School of Medicine and nine other researchers performed a multicenter study in which 63 men with coronary artery disease did treadmill exercises in chambers filled with varying amounts of carbon monoxide. At some point during treadmill exercise, such patients typically experience chest pain and other symptoms of ischemia. But the researchers found that even low levels of carbon monoxide -- equivalent to those allowed by the EPA -- accelerate the onset of chest pain and abnormal electrocardiograms. The study, reported in the No. 23 NEW ENGLAND JOURNAL OF MEDICINE, suggests that cigarette smokers -- who are exposed to additional carbon monoxide doses from their habit -- run an even greater risk of angina attacks and should make special efforts to avoid exercising in traffic-congested areas or working in such monoxide-rich environs at toll-booths or tunnels.