Chapter 3 Environmental causes of cancer

Abstract

Publisher Summary This chapter discusses the environmental causes of cancer. There is firm evidence that smoking or chewing tobacco, use of oral snuff, and drinking alcohol are causal in oral cancer. Additional promoting factors are betel nut and lime. People working in manufacturing or sale of alcohol have increased rates of lip cancer. Important confirmatory evidence comes from a study of migrant populations. In migrants who continue to chew tobacco and betel nut, the incidence is as high as in the original population. When the same migrants go to Fiji, on the other hand, they stop this habit, and the incidence of the cancer falls to that of the indigenous population. There is consistent strong evidence that the intake of alcohol increases the risk of cancers of the oral cavity, pharynx, larynx, esophagus, and liver. Details of the carcinogenic risks are given in International Agency for Research on Cancer (lARC) (1988). Much evidence comes from the study of populations abstaining from alcohol, such as Mormons in the U.S., and from comparing findings with those from populations, such as brewery workers, who are exposed to a higher than average intake of alcohol. Further confirmation comes from a definite dose relationship. The relationship between viruses and cancer is complex. For example, although certain viruses, such as herpes simplex can induce cancer, the tumor at a later stage does not appear to harbor the virus. Herpes simplex virus Type 2 is known to produce mutations in the cellular genome, and these must be the first step in cancer formation.