Historical cohort studies in three arsenic poisoning areas in japan

The results of historical cohort studies of three arsenic poisoning incidents in Japan are presented. The first episode was in a small mountainous community near an arsenic mine and refinery, at Toroku, where patients with chronic arsenism were certified by application of the Pollution Health Damage Compensation Law. The second area was in a small town, Namiki-cho, near Nakajo-machi, where wells were poisoned by arsenic produced in an arsenic(III) sulfide factory. As to the third cohort, eight residents of Nishikawa-machi who ingested well-water suffered arsenic poisoning about 35 years ago. The standardized mortality ratios were used in analyzing these data. Excesses of cancer mortality, especially lung cancer, were observed among the subjects in these areas. In Japan, there are many arsenic poisoning episodes, involving for example soy-sauce poisoning, powdered-milk poisoning and other incidents associated with arsenic mines. Thus it is necessary to clarify the chronic effects of arsenic in these areas.