SierraScape October - November 2005
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by Ken Schechtman, PhD and Mario Castro, MD
With this issue of SierraScape, we begin a series of articles that focus on the association between environmental pollutants and health. Our goal is to provide brief summaries of published scientific reports that deal with this multifaceted issue. We are motivated by the conviction that the effectiveness of environmental activists will be enhanced if they can talk knowledgeably about the health effects of pollution because these effects resonate loudly with an acutely health-conscious public. Both authors are on the faculty of the Washington University School of Medicine and both have many years of experience as clinical and epidemiologic researchers.
Although it is not a traditional concern of environmentalists, we begin with a discussion of the association between second hand tobacco smoke and lung cancer because of the recent vote of the St. Louis County Council against a measure that would have barred smoking in most public places. Lung cancer kills more than 160,000 Americans annually and is the leading cause of cancer deaths in both men and women. Nearly 90% of these deaths are attributable to smoking by the cancer victim, and smokers have a lung cancer incidence as much as 30 times as great as nonsmokers. In addition to genetic and dietary factors, the 17 to 18,000 annual lung cancer deaths among nonsmokers result from a variety of environmental causes that include ionizing radiation, asbestos, radon gas in the home, and particulates in outdoor air pollution. But the most important cause of lung cancer in nonsmokers may be exposure to second hand smoke.
A summary of the literature on this latter association by Brownson and colleagues was published in 1998 by the journal Epidemiologic Reviews. It confirmed the conclusions of prior reviews by the US Environmental Protection Agency, the California Environmental Protection Agency, and the National Academy of Sciences, all of which found a strong link between environmental tobacco and lung cancer. Brownson et al reviewed 23 separate scientific reports from eight countries. Most of these papers compared lung cancer rates in the nonsmoking spouses of smokers with lung cancer rates among the nonsmoking spouses of nonsmokers. In 20 of the 23 studies, the lung cancer rate among the exposed individuals was greater than among the individuals who were not exposed to second hand smoke. The US EPA study concluded that exposure to environmental tobacco smoke is responsible for some 3000 annual lung cancer deaths among nonsmokers in the United States. This means that about 18% of all lung cancer deaths among nonsmokers can be attributed to second hand smoke. Applying these data to the 2.5 million people who live in the St. Louis metropolitan area yields the conclusion that about 27 nonsmokers in the St. Louis area can be expected to die annually from lung cancer because they have been exposed to environmental tobacco smoke. If the burden of second hand tobacco is not reduced, these numbers mean that some 2000 people currently living in and around St. Louis will eventually die of lung cancers caused by this preventable environmental cause.
One final point is that lung cancer among nonsmokers is only one health consequence of second hand smoke. Such exposure has also been linked to increased nonsmoker rates of several cardiovascular diseases, emphysema, chronic bronchitis, and asthma. Indeed, the total number of nonsmoker deaths from these diseases that result from environmental tobacco smoke almost certainly exceeds the number of nonsmoker lung cancer deaths caused by second hand smoke.
We conclude that while environmental tobacco smoke may not be a traditional focus of environmental activists, it is a pollutant with major public health consequences for the nation and for the St. Louis area.