AS MANY as 60 000 nonsmokers die each year in the US from heart disease brought on by passive smoking, say two American medical researchers. The evidence from scores of studies is now overwhelming, say Stanton Glantz and William Parmley of the University of California, San Francisco.
In the most comprehensive review of the evidence so far, Glantz and Parmley argue that 鈥渆nvironmental tobacco smoke鈥� mounts a multipronged attack on the cardiovascular system, and that nonsmokers are particularly susceptible. 鈥淭his might be so because even small amounts of chemicals in tobacco smoke have large effects on the heart,鈥� they say.
Chemicals in tobacco smoke damage the cardiovascular system in many ways, say the researchers. Carbon monoxide in tobacco smoke displaces oxygen from red blood cells so that less oxygen reaches the heart. And the oxygen that does reach the heart is used less efficiently because chemicals in smoke lower the levels of a key enzyme called cytochrome oxidase.
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Smoke activates platelets in the blood, making clot formation more likely. Activated platelets also damage the inner walls of arteries, triggering atherosclerosis, the dangerous clogging of blood vessels. And nicotine increases the damage to the heart that follows a heart attack by increasing the build-up of damaging free radicals.
The review, published last week in the The Journal of the American Medical Association, also shows that nonsmokers are far more susceptible to these effects than might be expected. Smokers have a three times greater risk of developing heart disease than a nonsmoker who is not regularly subjected to environmental smoke. But even though nonsmokers who are continuously exposed to second-hand smoke inhale far less than a smoker, they have an increased risk of 30 per cent 鈥� a figure out of all proportion to their exposure.
Glantz and Parmley say this difference in sensitivity should be taken into account by policy makers. 鈥淭he tobacco industry loves talking about what they call 鈥榗igarette equivalents鈥� 鈥� saying you鈥檇 have to be in a smoky bar for a thousand hours in order to breathe the equivalent of one cigarette,鈥� says Glantz. 鈥淲e鈥檙e saying that this kind of comparison just doesn鈥檛 make sense.鈥�
The JAMA article comes when anti-smoking legislation is on the increase in the US. The Occupational Safety and Health Administration, the government body responsible for regulating conditions in the workplace, is proposing new rules that would ban or seriously restrict smoking in every workplace. Already, nearly every state in the country has some form of antismoking legislation, much of it inspired by the Environmental Protection Agency鈥檚 declaration that second-hand smoke is a carcinogen. The tobacco industry is suing the EPA, claiming its conclusion was based on faulty science.
Nor does the tobacco industry care for the article. The Tobacco Institute, which represents cigarette manufacturers in the US, says the researchers鈥� views 鈥渄o not represent mainstream scientific opinion鈥�. In a statement released last week the institute points out that two reports published in 1986 by the US Surgeon General and the Nation Academy of Sciences failed to find a link between second-hand smoke and heart disease, and it says Glantz and Parmley ignored several other important studies that found no link. It also claims that Glantz is 鈥減erhaps the leading anti-tobacco political activist in the US鈥�.
鈥淭hat鈥檚 very flattering,鈥� says Glantz. 鈥淏ut the action I take to try to promote public health is because of what I know about the science, not the other way around.鈥� He and other experts point out that since 1986 a wealth of evidence has been amassed to support the heart disease link. Glantz says the studies left out of the review were those sponsored by The Tobacco Institute.
Far from being a fringe viewpoint, the researchers鈥� conclusions are widely held, says Homayoun Kazemi, professor of medicine at Harvard Medical School. 鈥淭he adverse effects are there 鈥� there鈥檚 just no way of ignoring them,鈥� he says. 鈥淲ith the exception of the tobacco companies, everybody else is convinced.鈥�