Misconceptions on Pollution and the Causes of Cancer

According to the latest update from the National Cancer Institute (February 1988), "the age adjusted mortality rate for all cancers combined except lung cancer has been declining since 1950 for all individual age groups except 85 and above."['] That represents a 13-percent decrease overall, 44 000 deaths below expected, and a 0.1-percent increase in the over-85 group (unless otherwise noted, all statistics given in this article refer to the USA.) The types of cancer deaths that have been decreasing during this period are primarily stomach (by 75 percent, 37 000 deaths below expected), cervical (by 73 percent, 11000 deaths below expected), uterine (by 60 percent, 9000 deaths below expected), and rectal (by 65 percent, 13 000 deaths below expected). The types of cancer deaths that are increasing are primarily lung cancer (by 247 percent, 91 000 deaths above expected), which is due to smoking (as are 30 percent of all U.S. cancer deaths), and non-Hodgkin's lymphoma (by 100 percent, 8000 deaths above expected). Changes in incidence rates and effects of treatment are also relevant in interpreting the changes in mortality rates.". 21 Incidence rates have been increasing for some types of cancer. In their definitive study on cancer trends,I2I Sir Richard Doll and Richard Pet0 point out that, although incidence rates are of interest, they should not be taken in isolation, because trends in the recorded incidence rates are biased by improvements in the level of registration and diagnosis. Even if particular types of cancer can be shown to be increasing or decreasing, establishing a causal relation among the many changing aspects of our lives is d i f f i c ~ l t . ~ ~ ' ~ ~ There is no persuasive evidence that life in the modern industrial world has in general contributed to cancer deaths.['. '3 13] Cancer is fundamentally a degenerative disease of old age, although exogenous factors can increase cancer rates (e.g., cigarette smoking in humans) or decrease them (e.g., caloric restriction in Fo r mammalian species, cumulative cancer risk increases with approximately the fourth power of age, both in short-lived species such as rats and mice (about 30 % have cancer by the end of their 2-year life