Studies of population groups have provided, during the past year, clues to the causes of vari-ious kinds of cancer. A report on stomach cancer in Iceland and another on skin cancer in Taiwan highlighted the importance of environmental factors in cancer induction. In the Icelandic study, a relationship was reported between stomach cancer and dietary differences among various occupational groups. More specifically, the results appear to support evidence of a relationship between stomach cancer and consumption of home-smoked and singed foods. In Taiwan a clear dose-response relationship was established between the frequency of skin cancer and the arsenic content of the well water used by villagers in different localities.
A report on stomach cancer in Iceland revealed that mortality rates were highest among farmers, lowest among white collar workers. In relating occupation to diet, it was found that farmers consumed more home smoked and singed foods than any other group and, consequently, more polycyclic aromatic hydrocarbons (PAH). Compared to commercial products, these home preparations may contain 20 times as much 3,4-benzo-pyrene. a PAH that is one of the most potent carcinogens in laboratory animals. Variations in occupations, urban-rural living, and dietary sources of PAH thus appear to be directly related to stomach cancer mortality in Iceland. (Sigurjonsson, J.: Occupational variations in mortality from gastric cancer in relation to dietary differences. Brit. J. Cancer 21: 651-656, December 1967.).
First reports have become available of some of the results of long-term studies of the cancer experience of Japanese migrants to the United States and their children born in this country. It was found that both groups continued to experience the high stomach cancer and low breast cancer risks characteristic of homeland Japanese but that their risk of colon cancer changed from the low Japanese to the high United States rate.
Initial results of a search for clues to cancer causes through studies of persons with multiple cancers were reported. Data obtained from two large New York cancer centers showed that patients with leukemia, lymphoma, or myeloma were more likely than persons in the general population to develop skin cancer, but that their risk of a second more serious malignancy was not increased.
A review of deaths from childhood neuroblastoma occurring from 1950 through 1964 has shed interesting light on the possible causes of this disease. Epidemiologists found an apparent excess number of deaths in certain geographic areas at certain times and noted that neuroblastoma was most often diagnosed in the first year of life. These observations suggest an environmental factor affecting the child before birth.