Parents’ Smoking Linked to Children’s Lung Cancer : Medicine: Early exposure to secondhand smoke appears to cause 1 in 6 cases in nonsmokers, study finds.
About one in six cases of lung cancer in nonsmokers appears to be caused by long-term exposure to secondhand smoke at home during childhood, according to a study that for the first time suggests that parents’ smoking habits can eventually kill their children.
The study, published today in the New England Journal of Medicine, found that growing up in a household in which two parents regularly smoked could double a person’s risk of developing the lethal form of cancer later in life.
The finding, which remains to be confirmed in additional studies, adds a new dimension to the contentious public debate over the health effects of involuntary, or passive, smoking and over the desirability of banning tobacco smoking in public places.
“I think it just strengthens the case for limiting environmental tobacco smoke,” said Dr. Peter Greenwald of the National Cancer Institute, a co-author of the paper. “It strengthens the case for policies that protect the freedom of people to breathe clean air.”
There has long been evidence, though controversial, that some nonsmokers may develop lung cancer from living with a smoking spouse. And it is known that smokers’ children, when young, are especially susceptible to respiratory infections such as bronchitis and pneumonia.
But the new study is the first to find a link between growing up with smokers and developing lung cancer decades later, researchers said. If the finding is confirmed, they said, it may create a new impetus for people to limit or abandon smoking.
Experts in the field said the findings underline the importance of parents not smoking in the presence of their children, especially in cars and unventilated spaces. They also said physicians must continue to educate parents about how they may be harming their children.
“Adults may be more sensitive to an appeal to stop smoking not for their own sake but for the sake of protecting their children,” said Dr. Ronald M. Davis, director of the Office on Smoking and Health at the U.S. Centers for Disease Control.
Dr. Dwight T. Janerich, the Yale University epidemiologist who headed the study, said about 22,000 nonsmokers develop lung cancer in the United States each year, including about 7,000 who never smoked. Of those, 1,500 cases may stem from childhood exposure, he said.
Contrary to some earlier studies, Janerich’s study did not find any increased risk of lung cancer among the nonsmoking spouses of smokers. Nor did it find any increased risk from exposure to secondhand smoke in workplaces or social settings.
Representatives of the tobacco industry on Wednesday chose to emphasize those findings rather than the finding of cancer risk in the children of smokers. Like the researchers, they stressed the need for additional studies.
“It’s a very tentative finding because they qualified it, I think, very much,” said Steve Parrish, a vice president at Philip Morris Cos. He contended that most studies on the effects of involuntary smoking have turned up “no significant increase” in cancer risk.
The new study, by researchers from seven institutions, compared 191 nonsmokers with lung cancer to 191 healthy nonsmokers who served as controls. The researchers collected information on the participants’ secondhand-smoke exposure at home, at work and in social settings.
They concluded that household exposure to 25 or more “smoker years”--the equivalent of two parents smoking for 12 1/2 years-- during a person’s childhood and adolescence doubled his or her long-term lung cancer risk. Exposure of less than 25 smoker years did not increase the risk.
“This amount of exposure is equivalent to living with more than one smoker throughout childhood and adolescence--a high but not uncommon level of exposure,” the researchers wrote.
The group concluded that about 17% of all lung cancers in nonsmokers “can be attributed to exposure to passive smoke in the household during childhood and adolescence.”
The researchers do not know the mechanism by which exposure in childhood might raise one’s cancer risk, but they suggested that the susceptibility of smokers’ children to respiratory infections might trigger changes in the lungs that lead eventually to cancer.
(A 1986 report by the U.S. surgeon general found that infants of parents who smoke are more likely than other infants to be hospitalized with bronchitis and pneumonia. They also have more frequent respiratory symptoms and a slower rate of growth in lung function.)
Specialists in the field said they were not surprised by the finding.
“It makes eminent sense that this is true,” said Joseph W. Cullen, director of the AMC Cancer Research Center in Denver. “The earlier the exposure and the greater the exposure, the greater the probability of disease. So from a biological point of view, it makes sense.”
Dr. Richard J. Jackson, chairman of the committee on environmental hazards for the American Academy of Pediatrics, said: “We’ve sort of long suspected this was going on. . . . I’m glad someone’s actually gotten down and done the study.”
Nevertheless, the researchers noted that such studies rely on people’s recollections and are vulnerable to bias and error. For example, people who develop lung cancer may be more likely than healthy people to remember their parents’ heavy smoking.
Responding to the new findings, Dr. David Burns, an associate professor of medicine at UC San Diego who served as senior scientific editor for the surgeon general’s 1986 report on involuntary smoking, suggested that there is “a societal responsibility” to limit smoking in schools and day-care centers.
Forty states now have laws restricting smoking in public places, up from 20 states in the mid-1970s. More than half of all large companies have policies restricting smoking. Smoking has also been banned from 99% of all domestic airline flights.
At least two states--New Jersey and Kansas--have banned smoking on school premises, according to Davis of the Office on Smoking and Health. He called day-care centers “an important setting for banning smoking,” but said little is known on where it is done.
The Los Angeles Unified School District prohibits students from smoking on school grounds, but allows adults to smoke in designated areas, such as faculty lounges.
But the Board of Education is considering extending that ban to adults. Board members will vote this month on a measure that would forbid smoking by anyone on district property--including campuses, cars and outdoor athletic fields.
