"Passive smoking," or environmental tobacco smoke (ETS), has significant health consequences for nonsmokers. Exposure to cigarette smoke at home or at work increases a nonsmoker's risk of coronary artery disease by up to 30%. And each year between 37,000 and 40,000 nonsmokers die of cardiovascular disease caused by cigarette smoke. These sobering statistics have launched many legislative efforts to ban smoking in public places. And two recent studies add weight to those arguments.

Data from the Nurses' Health Study document that regular exposure to cigarette smoke at home or at work nearly doubles a woman's risk of heart disease. Researchers -- including Harvard Heart Letter editorial board members Walter C. Willett, MD, and Charles H. Hennekens, MD -- focused on 32,046 women who were 36-61 years old in 1982. At that time, all of these women reported that they had never smoked, and all were free of known coronary artery disease, stroke, or cancer.

Although all the women were nonsmokers, about 80% of them reported regular or occasional exposure to environmental tobacco smoke at home or work. More than 10,000 of the women reported regular exposure. During the next 10 years, 25 of these women died from coronary artery disease and another 127 had nonfatal heart attacks. After adjusting for other heart-attack risk factors, researchers found that women reporting regular exposure to cigarette smoke had a 91% increase in the risk of heart disease. Those who reported occasional exposure had a 58% increase in risk. While either workplace or home exposure was associated with an increase in heart-disease risk, that risk was greatly increased for women exposed to cigarette smoke both at home and at work.

In short, regular exposure to passive smoking at work or home increased the risk of coronary artery disease among nonsmoking women -- a group generally considered at low risk for heart attack. This study illustrates that environmental tobacco smoke is a significant risk factor for heart disease. (Circulation, Vol. 95, No. 10, pp. 2374-2379.)

Cigarette Smoke and Atherosclerosis

The ARIC (Atherosclerosis Risk in Communities) study examined the effects of both "active" and passive smoking on blood vessels in 16,000 people, and the news is disturbing. To assess the effects of cigarette smoke on the progression of atherosclerosis, researchers used ultrasound to measure the thickness of the carotid arteries (the arteries in the neck that carry blood to the brain). This measurement was used to track the progression of atherosclerosis over three years in five groups:

• smokers
• past smokers who were regularly exposed to environmental tobacco smoke (ETS)
• past smokers who had not been exposed to ETS
• people who had never smoked but were exposed to ETS
• never-smokers who did not report ETS exposure

Over the study period, atherosclerosis progressed 50% in current smokers and 25% in past smokers. Compared to those not exposed to ETS, atherosclerosis increased by 20% in those with ETS exposure. That's roughly 34% of the rate for active smokers. And the detrimental effects of smoking proved much worse for people with diabetes or high blood pressure.

Does how much a person smokes influence the progression of atherosclerosis? Researchers also found that the greater the number of cigarettes smoked per day over time, the faster atherosclerosis progressed. But when comparing people who had smoked the same number of cigarettes, it didn't matter whether the study participants were current or past smokers; atherosclerosis progressed at the same rate in both groups. And atherosclerosis progressed 24% faster in former smokers than in never-smokers, implying that some of the smoking's effects on blood vessels may be irreversible.

Data from these studies emphasize the dangers of environmental tobacco smoke and will inform the debate that surrounds banning smoking in public places. The suggestion that some of the effects of passive smoking may be permanent does not mean smokers shouldn't bother kicking the habit.