Study Contends Secondhand Smoke Won't Kill You

But critics dismiss it as bad science paid for by tobacco industry

Amanda Gardner

Amanda Gardner

Published on May 15, 2003

THURSDAY, May 15, 2003 (HealthDayNews) -- Secondhand smoke may not be as harmful as thought -- or at least it may not kill those exposed to the smoker. But they do face an increased risk for such chronic respiratory problems as bronchitis and emphysema.

That's the conclusion of a highly controversial study in the May 17 issue of the British Medical Journal that found secondhand smoke did not significantly increase the risk of death from lung cancer or coronary heart disease for non-smoking spouses of smokers.

The study immediately fanned the ongoing debate over the dangers of inhaling other people's cigarette smoke.

Several of the world's top scientists meeting for a conference in Miami, including a former U.S. Surgeon General, slammed what they called a tobacco industry-funded study that flies in the face of repeated research that documents the dangers of secondhand smoke.

"This study is just the latest in a long string of studies designed to deny the evidence and confuse the public," Dr. Julius Richmond, the U.S. surgeon general from 1977 to 1981, said in a statement. "The first study linking secondhand tobacco smoke and lung cancer was published 22 years ago when I was Surgeon General, and the evidence has only become stronger since then."

The American Cancer Society also attacked the study's credibility.

"We are appalled that the tobacco industry has succeeded in giving visibility to a study with so many problems it literally failed to get a government grant," Dr. Michael J. Thun, the society's national vice president of epidemiology and surveillance research, said in a statement. "The American Cancer Society welcomes thoughtful, independent peer review of our data. But this study is neither reliable nor independent."

And the British Medical Association issued a statement criticizing the study. "It reanalyses a small part of the data from a study that was dropped by its original funders, the American Cancer Society. Most of the data has been around for decades (the study was begun in 1959) but was judged by many expert groups to be inadequate to accurately measure passive smoking."

However, Geoffrey Kabat, a co-author of the study and an independent researcher, defended the merit of the research.

"It's a very large study and very carefully conducted," said Kabat, formerly an associate professor of preventive medicine at the Stony Brook University School of Medicine in New York. "It's one of the biggest studies on this issue. It's conducted very meticulously. They're barking up the wrong tree."

And co-author James Enstrom, a researcher at UCLA's School of Public Health, also said, "I can fully defend the independence [of this research]."

Asked about the study's source of funding, Enstrom said he received money from the Center for Indoor Air Research, which was funded by tobacco companies until it was disbanded in 1999.

"Basically they gave me the money at the same time they went out of business, and they left me alone. And I've never spoken to the tobacco industry since," he said.

Added Kabat: "This is a peer-reviewed study. There's no way that the tobacco industry is going to influence reporting on the results. The study reports what we found."

For the British Medical Journal study, the researchers revisited people who had participated in an American Cancer Society cancer-prevention study that took place from 1959 until 1998. The original study had 118,094 participants. The authors of the new study restricted their analysis to 35,561 participants who had never smoked as of 1959 and who had a spouse in the study who did smoke. In mid-1999, these people were asked to fill out a two-page questionnaire on smoking and lifestyle.

The researchers concluded secondhand smoke did not significantly increase the non-smoking spouse's chances of dying from coronary heart disease or lung cancer, regardless of how much the spouse smoked.

"Even people who seemed to be exposed to higher levels of spouse's smoke didn't have a statistically higher risk of lung cancer or heart disease," said Kabat.

Nonsmokers, however, did have an increased risk for chronic obstructive pulmonary disease (COPD), a term that refers to chronic bronchitis and emphysema, the study found.

"For COPD, in both men and women, we found a 60 percent increase in people who had heavy exposure," Kabat said. "That is suggestive of an effect."

Not surprisingly, smokers themselves had a higher risk for coronary heart disease, lung cancer and chronic obstructive pulmonary disease. And that risk increased with the number of cigarettes they smoked, the researchers found.

Other experts questioned whether death rates from lung cancer and heart disease are appropriate ways to assess the harmful effects of secondhand smoke.

"Cardiovascular disease mortality may not be a good measure of non-fatal effects such as myocardial infarction, stroke, etc.," said Frank Gilliland, an associate professor of preventive medicine at the Keck School of Medicine at the University of Southern California in Los Angeles.

Gilliland is the lead author of a study in the May 15 issue of the American Journal of Epidemiology that found exposure to secondhand smoke in the house increased absenteeism among children with asthma and, to a lesser degree, children without asthma.

Referring to the new study, Dr. Norman H. Edelman, consultant for scientific affairs for the American Lung Association, said, "It's an interesting contribution, but the answer certainly isn't in."

Based on several previous studies, the American Heart Association, the U.S. Surgeon General and other organizations have concluded that "environmental tobacco smoke" -- secondhand smoke -- increases the risk of coronary heart disease and lung cancer by about 25 percent.

The topic is a controversial one because of difficulties in measuring and assessing damage from so-called passive smoke.

But the latest study isn't likely to change regulations or sentiments about smoking, particularly in public places.

"Our smoking regulation has to do with the workplace, which is a qualitatively different situation," said Dr. John Rich, medical director of the Boston Public Health Commission, which on May 5 banned smoking in the workplace.

"Workers are in a setting for eight hours or so where they're exposed not to the smoking of one person like a spouse, but high levels of tobacco smoke in the air," Rich said. "When one looks at evidence about workers, it's much more clear that they suffer a risk of 50 percent in some studies of lung cancer and the like."

And even the authors of the new study are against relaxing smoking restrictions, even if their evidence appears ambiguous.

"If it's hard to say with certainty the increased risk of someone who smokes one cigarette a day religiously every day for 40 years, you can imagine how hard it is to say anything about this. There's no reason to think that from one whiff of smoke or one evening out that you're going to be set on the road to heart disease or lung cancer or other diseases," said Kabat, who is a nonsmoker.

"[But] there's no reason why you should be subjected to inhaling other people's tobacco smoke," he added. "People should have the right not to breathe this extra form of air pollution."

More information

The U.S. Centers for Disease Control and Prevention has more information on smoking and lung disease. Visit the American Lung Association for information on quitting smoking.

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