Risk of Cancer Deaths among Agricultural Households in Kanto Area, I

Cancer Deaths among Agricultural households

Abstract

Agriculture, as an occupation, differs from other occupations in the following respects. First, agricultural works often involve not only farmers but their family members such as wives, children and their old parents even. Secondly, agricultural labor is out-door and seasonal, using a variety of chemicals for agricultural purposes. Their life-style is somewhat conservative and different from others in many respects including their eating habits (Ministry of Health and Welfare, 1977). Thirdly, agriculture is mostly a hereditary occupation, and thus they are very likely natural-born people of their resident districts. It may be important to disclose the cancer incidence or mortality of farmers and their families, who can be regarded to be a characterized population as described above. The importance of this study can be emphasized not only by the fact that agricultural households occupied one-sixth of Japanese total population, but also by the promising possibility of finding some important clues to the study of causes and/or prevention of human cancers. In fact, some cancers have been found to be agriculture-associated; e.g., positive association of stomach cancer (Hirayama, 1971), gallbladder and bile ducts cancer (Tominaga et al., 1979); negative one of colon cancer (Haenszel et al., 1980). Additionally, recent studies in Saitama prefecture revealed that liver (Sasaba and Kubo, 1982) and esophageal cancers showed high odds ratios in farmers and their families. Here the high risk of liver cancer was observed in a restricted area of Saitama. The purpose of the present study is then to analyze the cancer deaths among agricultural households (farming families) in comparison with non-agricultural ones, and to offer useful information and/or suggestion for the research of cancer-related factors in agricultural environments. This study is focused on the farming families of about four million population living in Kanto area, where the climate, geology and soil are rather uniform. The results on Kanto area is compared with those obtained for the whole of Japan, and hence the characteristics of Kanto farming families in cancer deaths will be remarked. In the analysis of cancer deaths, we consider a number of cancer sites and estimated the risk of agricultural life-style for each site, since the agricultural life is characterized not only in an occupational aspect but in many other aspects of living circumstances. We have to examine or confirm the association of those cancers with agriculture which have been suggested so. The examination on many other cancers may also add a new aspect to the traditional concept on this association. It is also meaningful to analyze the agespecific cancer risks of agricultural households. This further analysis answers the two questions: which age group of agricultural households shows a specially high or low risk of cancer; in which ages of the agricultural households the agriculture-linked factor(s) causing a high or low risk of cancer affects on them. The latter is estimated in terms of so-called multistage theory using some reasonable assumptions.