Methylmercury and selenium in umbilical cords of inhabitants of the Minamata area

Abstract

IT has been established that selenium exerts a protective effect against the toxicity of methylmercury1–5. A study on higher marine mammals suggested that the antagonism between selenium and mercury may result in a marked accumulation of both elements in the organs of the animals6, and a similar observation has been made in the laboratory7. In retrospect, this beneficial mechanism was operative, though incompletely, during the period when a wide area around the city of Minamata was polluted with methylmercury discharged from a factory involved in the production of acetaldehyde : the organs of men and cats who died from Minamata disease showed elevated levels of selenium as well as mercury8,9. Furthermore, the highest concentration of these substances was noted in the liver of an apparently healthy cat (Hg, 301 p.p.m.; Se, 89.7 p.p.m.) caught in a village 10 miles north of Minamata8,9. We report here that the umbilical cords of the inhabitants of Minamata seem to reflect a chronological transition in methylmercury pollution but no corresponding shift in selenium levels.