But there is a good deal of positive evidence in the two chapters dealing with cancer that we now know so much more about cancer that we could, if we had the will, do a great deal about decreasing the incidence and prevalence of cancer. In 1987 in USA one million people developed cancer and half a million died from it. The distribution was not even and certain areas had much more than other areas. There are three different types of cancers which have different relationships to geographical factors. Foster discusses only esophageal and breast cancers.
Males get esophageal cancers more frequently than females.
In both cancers the incidence increases with increasing age. Causal factors in esophageal cancers include genetic, which are minor, lifestyle and diet which are major. Smoking and alcohol have a direct connection by irritating the epithelium of the throat and esophagus. But there is a relationshp to salt in the soils. Foster has calculated that the amount of cancer can be predicted by the following equation.