Metabolism of chemical carcinogens

Abstract

In the mind of the lay and even professional public, cancer of various types has been considered to be a “spontaneous” condition (Weisburger, 1973a). The concept that some types of cancer might, however, be caused by environmental factors traces back to the observation of Pott in the late eighteenth century that human scrotal cancer in Great Britain was associated with the occupation of his patients, namely sweeping chimneys. Since that time, people in other occupations have been demonstrated to have certain risks of developing cancer at some sites. Overall, however, occupational cancers are relatively rare events which affect only limited numbers of individuals. The bulk of human cancers were until recently considered to stem from unknown elements. It was a consideration of international incidence rates of various types of cancer, and the fact that the incidence depends in part on the site of residence, which underwrote the concept that many types of human cancer are caused, mediated, or modified by environmental factors (Wynder and Mabuchi, 1972; Higginson and Muir, 1973). Thus examination of the incidence of two types of cancer of the digestive tract, namely stomach cancer and large bowel cancer, in populations in Europe, Latin America, Japan, and the North American continent indicated clearly that they have quite different causative and modifying elements, but both are associated mainly with dietary factors. Lung cancer, on the other hand, has been definitely traced to the personal habit of smoking cigarettes.