Autopsies Link Secondhand Smoke, Cancer
The first direct medical evidence that secondhand smoke can damage the lungs of nonsmokers has been produced by an international team led by researchers at Harvard University.
The team performed autopsies on 30 nonsmoking women and found that the lungs of smokers’ wives contained a significantly higher number of precancerous abnormalities--such as cellular proliferation and damage--than did the lungs of nonsmokers’ wives.
Previous studies showing a higher incidence of lung cancer among wives and children of smokers have been based on statistical evidence and suggest that at least 4,000 people die of lung cancer each year as the result of secondhand smoke. But the tobacco industry has argued that the reported link between lung cancer and passive smoking could come from biases in the collection of epidemiological data.
The new study, reported today in the Journal of the American Medical Assn., appears to show that those statistics were not biased, proponents say.
“It is a pathfinding study,” said Dr. Morton Lippman, a professor of environmental medicine at the New York University Medical Center who recently chaired an Environmental Protection Agency panel evaluating the hazards of secondhand smoke. A preliminary version of that risk assessment, released in June, concludes that environmental tobacco smoke causes lung cancer in nonsmoking adults, increases the risk of respiratory infection in children and exacerbates symptoms in children with asthma.
“We have taken the position for several years that the epidemiological data are very convincing,” added Dr. Norman Edelman, a pulmonologist at the Robert Wood Johnson Medical School in New Brunswick, N.J., who serves as a consultant to the American Lung Assn.
“But what this does,” he said of the new study, “is give us visual evidence, biological confirmation of that. That’s important both in terms of science and in terms of public perception. . . . It doesn’t tell us anything we don’t know, but in science and public policy we like to confirm what we know from different points of view.”
The tobacco industry, however, immediately challenged the study. Because of the small number of subjects involved in the study, said Tom Lauria, a spokesman for the Tobacco Institute, the data “is likely to be subjected to many biases and confounding factors. . . . This is basically an epidemiology study with an autopsy attached, but the possibility for error is much greater because you are talking about a biological finding. So the usefulness of this study is many times less than what you would expect.”
But Edelman noted that for years the tobacco industry made similar arguments about the epidemiological data linking smoking to lung cancer. “They put up that smoke screen for years and years and years” before researchers demonstrated that smoking causes cancer in animals, he said. “There’s a kind of parallel now in that this provides the same kind of visual evidence” as the studies in animals.
According to the American Heart Assn., 50 million nonsmoking adults over the age of 35 are exposed to secondhand smoke and about 50% of American children live in families with one or more smokers. A June Heart Assn. report estimated that in addition to its effects on lung cancer, secondhand smoke could be a contributing factor in the deaths from heart disease of 40,000 nonsmoking Americans every year.
In obtaining the new results, a team headed by Dr. Dimitrios Trichopoulos, an epidemiologist at the Harvard School of Public Health, studied lung tissue obtained from autopsies of 400 people who died in Attica, Greece, between 1986 and 1990. Such autopsies are mandatory in Greece when a death is due to external causes--such as violence or accident--or has resulted from sudden illness. None of the subjects died of lung cancer or respiratory disease.
The physicians determined the total number and severity of the abnormalities in the lung tissue of each subject and then compared it with the history of the subject. Only 41 of the victims were nonsmoking women: 17 were married to husbands who smoked, 13 were married to nonsmokers and no data was available for 11.
The researchers found that a significantly larger number of abnormalities were present in the lungs of smokers’ wives than in nonsmokers’ wives. The number of abnormalities could not be linked to any other factor, such as exposure to air pollution, occupation or area of residence.
“The dramatic impact of passive smoke on these women can be compared to approximately 10% of the effect on the lungs suffered by active smokers,” Trichopoulos said. This study, he added, “definitely shows that environmental tobacco smoke can cause damage in the lungs.”
