Recent Findings in Minamata Disease From a Population-based Study Conducted in 1971

Abstract

S-30A9-2 Background/Aims: It is well known that large-scale poisonings caused by methyl mercury occurred in Japan (Minamata, in the 1950s). However, there have been few population-based epidemiologic studies in Minamata. Therefore, we evaluated the effect of methyl mercury on neurological signs and hypertension using data from a 1971 population-based study. We also evaluated the association between hair mercury level and both outcomes. Methods: Villages in 3 areas were selected for study: the Minamata area (a high-exposure area), the Goshonoura area (a medium-exposure area), and the Ariake area (a low-exposure area). We used place of residence as the exposure indicator. We examined associations between methyl mercury exposure and the neurological signs as well as hypertension. Results: Total population was 1120 in the high-exposure villages, 1845 in the medium-exposure villages, and 1165 in the low-exposure villages. In the Minamata area, 87% (833) of the eligible population (aged 10 and older) participated in the 1971 investigations, in the Goshonoura area 93% (1450), and in the Ariake area, 77% (755). Compared with subjects in the Ariake area, the subjects in the Minamata area manifested neurological signs and hypertension more frequently. The highest prevalence odds ratio was observed for perioral sensory loss around the mouth (110; 95% confidence interval = 16–820). Furthermore, hair mercury levels were associated with perioral sensory loss in a dose–response relationship. Conclusion: Long-term exposure to methyl mercury has a strong adverse impact on neurological signs and hypertension among residents in a local community.