One of the world's most horrific environmental disasters--the 1950 and 60s mercury poisoning in Minamata, Japan--may have been caused by a previously unstudied form of mercury discharged directly from a chemical factory, research by the University of Saskatchewan (USask) has found.
By using state-of-the-art techniques to re-investigate a historic animal brain tissue sample, our research helps to shed new light on this tragic mass poisoning. Mercury persists for a long time in nature and travels long distances. Our research helps with understanding how mercury acts in the environment and how it affects people." Ingrid Pickering, USask professor, Canada Research Chair in Molecular Environmental Science
The study examining which mercury species could be responsible for the Minamata poisoning was published Feb. 12th in the journal Environmental Science & Technology . It is expected to prompt a wider re-assessment of the species of mercury responsible for not only the Minamata tragedy but perhaps also of other organic mercury poisoning incidents, such as in Grassy Narrows, Ontario.
Mercury-containing industrial waste from the Chisso Corporation's chemical factory continued to be dumped in Minamata Bay up to 1968. Thousands of people who ingested the mercury by eating local fish and shellfish died, and many more displayed symptoms of mercury poisoning including convulsions and paralysis.
"Something that was unknown at that time was that unborn children would also suffer the devastating effects of mercury poisoning, with many being born with severe neurological conditions," said USask PhD toxicology student Ashley James, the first author of the paper. "A mother may be essentially unaffected by the poisoning because the mercury within her body was absorbed by the unborn child."
The Minamata poisoning has been considered a textbook example of how inorganic mercury turns into organic mercury, and how a toxic substance propagates up the food chain to humans. For decades, it has been assumed that micro-organisms in the muds and sediments of Minamata Bay had converted the toxic inorganic mercury from the factory wastewater into a much more lethal organic form called methyl mercury, which targets the brain and other nervous tissue. This compound was thought to spread to humans from eating contaminated seafood.
Recent studies have suggested that methyl mercury itself may have been discharged directly from the Minamata plant.
But USask research--involving 60-year-old Minamata feline tissue samples--has found these assumptions may be misplaced.
Using a new type of spectroscopy and sophisticated computational methods, the USask researchers have found that the cat brain tissue contained predominantly organic mercury, contradicting previous findings and assumptions. The team's computer modelling was also able to predict which kinds of mercury waste compounds the chemical plant would be likely to produce. Related Stories
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