Many commentators have suggested that we are in the midst of a cancer epidemic caused by unknown environmental factors. For instance, citing links between cancer rates and pesticide use, Devra Lee Davis, an adviser to the U.S. assistant secretary for health, told the Atlanta Journal and Constitution that it is important for people to "control [their] exposure to elements in the environment."
But according to two recent studies, such claims are not merely wrong–they misdirect attention from known causes of cancer. Studies by the American Council on Science and Health and the National Cancer Institute both conclude that the appearance of rising cancer rates is explained in large part by better testing methods. Both studies bear even better news: For people under 55, the mortality rates for most cancers are actually declining.
Improved cancer-screening methods are responsible for creating an impression of higher cancer incidence rates, states the ACSH report. In 1980, for example, the breast cancer rate for women was 85.2 per 100,000. In 1987, it rose to 112.4 per 100,000, then declined the next two years.
This supports the view that early detection by increased use of mammography and other screening methods explains the "increase" of breast cancer in the 1980s. In fact, for the past 40 years, concludes the study, most forms of cancer have remained constant or even decreased (lung and AIDS-related cancers being notable exceptions).
The NCI study attributes much of the increase in breast and prostate cancer rates not merely to better screening techniques but to more frequent use of diagnostic tests. Hence, it concludes that most of the rise in reported incidence of both cancers is associated with earlier detection.
Far from implicating "unknown environmental factors," the studies agree that most cancers are related to known lifestyle factors: tobacco and alcohol abuse, diet, radiation, sexually transmitted diseases, and exposure to sunlight.
Given the depth of the research available, writes ACSH President Elizabeth M. Whelan, it is most important to focus on the "known causes of cancer, rather than misinforming the public about unreal threats to health, such as pesticides."