Science

Geoffrey Kabat | 10.16.2024 2:45 PM

In 2003, UCLA epidemiologist James Enstrom and I published a study of environmental tobacco smoke (ETS)—also called "secondhand smoke" or "passive smoking"—in the British Medical Journal (BMJ). Using data from the American Cancer Society's prospective study of 1 million adults, we concluded that ETS exposure was not associated with increased mortality.

Since that conclusion flew in the face of the conventional wisdom that had long driven state and local bans on smoking in public places, our study understandably sparked a controversy in the public health community. But the intensity of the attack on us in the pages of a medical journal—by critics who were certain that our study had to be wrong but typically failed to provide specific evidence of fatal errors—vividly illustrates what can happen when policy preferences that have taken on the status of doctrine override rational scientific debate.

A recent study by American Cancer Society (ACS) researchers underscores that point by showing that, contrary to what our critics asserted, the cancer risk posed by ETS is likely negligible. The authors present that striking result without remarking on it, which may reflect their reluctance to revisit a debate that anti-smoking activists and public health officials wrongly view as long settled.

Exposure to ETS is known to cause eye and throat irritation and to exacerbate preexisting respiratory conditions. In addition, it is simply disagreeable to many people (including me). But assessing the claim that ETS is potentially deadly requires dispassionate examination of the available scientific evidence.

That is not what Enstrom and I encountered when we published our BMJ paper. Critics were outraged by the article and demanded its retraction. But they were never able to satisfactorily explain why such an extreme step was justified.

Our Study

We addressed the main criticisms of our paper in a detailed authors' response. The journal's editor in chief defended the decision to publish the paper, enumerating its strengths and stating that failure to publish high-quality work distorts the scientific record. If anyone had found evidence of fraud or even serious errors in the paper, as some alleged, it would have been retracted. No one found any such fatal flaws.

Because we were aware of the difficulties in measuring secondhand smoke exposure, we went to great lengths to obtain fine-grained information from the California participants in the original ACS study of 1 million Americans, which was launched in 1959. We recontacted surviving members of the cohort and asked them additional questions about their exposure to cigarette smoke. Using data from multiple contacts with subjects, we were able to improve the quality of exposure information, which is the Achilles heel of most ETS studies. As a result of these measures, exposure information was more detailed and more reliable than in many previous studies.

To put the risk from secondhand smoke in perspective, we examined the association of active smoking with mortality from lung cancer, coronary heart disease, and chronic obstructive lung disease. We demonstrated dose-related associations of smoking with mortality in all three categories. This was true even for "light" smokers—people who smoked fewer than 10 cigarettes per day. That finding was important because it showed that our study was able to pick up the relatively small effect of light smoking.

The fact that we demonstrated a strong association between active smoking and mortality, which increased in a graded fashion with increasing levels of smoking in both men and........

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