ABSTRACT

Cancer is the second leading cause of death in many Western countries. More than 800,000 new cases of cancer are diagnosed each year in the United States, and over 400,000 die of cancer annually (National Cancer Institute, 1990; National Center for Health Statistics, 1986; National Research Council, 1989a; U.S. Department of Health and Human Services, 1988). The cause and possible control of cancer has been intensely investigated. It has been recognized that environmental factors have strong influences on the incidence of human cancer. Many chemical and physical agents in the environment have been identified or are suspected as human carcinogens. These include many directacting carcinogens, pro-carcinogens, co-carcinogens, and promoters.