Cancer prevention: assessing causes, exposures, and recent trends in mortality for U.S. males, 1968-1978.

This paper addresses some enduring issues concerning prevention of environmental and occupational cancer. The first part reviews methodological problems of estimating cancer risks and outlines some research priorities. The second part documents countervailing trends in chemical production during the past two decades, noting the doubling of some synthetic organic human carcinogens and the leveling off of some heavy metal carcinogens. The final section details recent increases in site-specific causes of cancer mortality for men old enough to have developed workplace cancers (ages 35 to 84), considering those cancers that have been linked with exposures to toxic chemicals and to cigarette smoking. This paper points out that Doll and Peto's (1981) analysis of U.S. cancer trends does not indicate some important increases in older males; they conclude that apart from cigarette smoking, there is no generalized increase in cancer for persons up to age 64. In fact, there has been a sharp reduction in cancer mortality for those under age 45. This reduction more than offsets increases in some cancers for those ages 45 to 65. Men ages 55 to 84 have experienced major increases in mortality for certain cancers plausibly associated with occupational exposures, including cancers of the brain, lung, and multiple myeloma. These older age groups have potentially sustained longer workplace exposures to carcinogens, some of which have 25-year or greater latencies. Changes in infectious diseases, workplace exposures, diagnostic trends, environment, and nutrition require further study.