1996 年 44 巻 6 号 p. 795-803
Geographical distribution of standardized mortality ratio (SMR) for biliary tract cancer (BTC) showed a characteristic clustering pattern; high in the northeastern regions and low in the southwestern regions of Japan. Among the 47 prefectures (corresponding to counties in the U. S.) with high SMRs, Niigata Prefecture has been the highest in both sexes for the last two decades. It was found that the cities, towns and villages in Niigata where the mortalities from BTC were high were correspondent with rice producing areas.
In addition, it was revealed that the sources of tap water in the cities with high SMRs in Niigata were commonly big rivers, whereas in those with low SMRs they were either reservoirs located in the mountains, underground water or small river originating from the mountains. Based on these findings, the contamination of tap water by agricultural chemicals form paddy fields was suspected as a cause of the high mortality from BTC. Among several chemicals examined, diphenylether herbicide, chlornitrofen (CNP) and its derivative (CNP-amino) were detected high in tap water in the cities with higher SMRs and they seem to be related to the occurrence of BTC, particularly of female gallbladder cancer.