Pollution, carcinogenesis and cancer prevention

Epidemiological and other data indicate that most cancer is due to environmental factors in the broader sense of the term and, therefore, presumably preventable to a great extent. Consequently, the identification of carcinogens in the environment is of fundamental importance in cancer prevention. Oncogene research has given new insight into the cellular signal pathways, as well as genetic alterations leading to neoplastic growth. This information provides a foundation for improvement of the current testing strategy for carcinogenic chemicals released into the environment. The testing protocols must take into consideration the carcinogenic agents that act through both genotoxic and non-genotoxic mechanisms. Also, it should be pointed out that human exposure often involves complex mixtures of chemicals, and the possibility of interactions between initiating and promoting carcinogens. Current test procedures rarely deal with such chemical interactions. Analyses of environmental factors responsible for the induction of cancer in humans indicate that naturally-occurring, rather than man-made, chemicals constitute a prevalent cancer risk. It must, however, be stressed that this conclusion applies to Western industrialized countries. In eastern European and developing countries, environmental pollutants, synthetic pesticides and other man-made chemicals very likely pose a larger cancer risk for the general population.