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 methylmercury^1–5. 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 mercury^8,9. 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 Minamata^8,9. 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.