Importance of environmental and occupational factors in cancer.

Geographic and temporal variations in cancer incidence, changes in migrants, differences between males and females, as well as case history studies are discussed. Cancers of the workplace can be divided into those related to "point-source" industrial pollution and those where the social milieu or "life-style" of the occupation play a role (e.g., job-associated cancers). In the future, considerably more effort is necessary in studying the life-style factors in specific occupational settings. It is important not to forget that occupational cancer is essentially an excess risk over the background risks.