A Case History; Minamata Mercury Pollution in Japan – From Loss of Human Lives to Decontamination

Abstract

At Minamata Bay in Japan, more than 100 people lost their lives and many thousands more were permanently paralyzed from eating mercury contaminated fish. In the long history of water pollution, this was the first known case where the natural bioaccumulation (in fish) of a toxicant from an industrial wastewater killed a large number of human beings. The mercury, discharged from a factory, was deposited on the bottom of the Bay and has remained there since the 1950's. The fate of the mercury was traced by measuring 268 mercury concentrations in the surface sediments at Yatsushiro Sea (outside of the Bay) during the last 14 years. Twenty-four sampling stations were established to collect samples at the same location every year. Samples were analyzed for total mercury concentrations. The concentrations of mercury in the surface sediments at the Sea were not alarming. Only 33 samples exceeded a mercury concentration of 1 ppm. The dispersion of the mercury from the Bay, however, was clearly documented with the data. On average, 3.7 tons of the mercury was transported outside from the Bay every year. A decontamination project started in 1984 dramatically decreased the flow of mercury from the Bay to the Sea. A historic rainfall in 1982 also ‘purified' the surface sediments. Organic mercury concentration in the sea water was 5.1 ng/l while total mercury was 120 ng/l at the center of the Bay in 1985.

Comparative assessment of Azolla pinnata and Vallisneria spiralis in Hg removal from G.B. Pant Sagar of Singrauli Industrial region, India

“…However, problem of Hg pollution is a matter of serious concern at local, regional as well as global scale (Rai 2007a). In Japan, 2,252 peoples have been affected and 1,043 have died due to Minamata disease, caused by elevated mercury pollution from a chemical plant (Kudo and Miyahara 1991). Even at very low concentration, Hg can cause permanent damage to the human central nervous system because LD 50 (rat) of Hg is 1-1.2 mg Hg 2+ /kg (Holtt and Webb 1986).…”

Protecting aquatic organisms from chemicals: the harsh realities

“…About 100 people, mainly the physiologically weak, died, and many more suffered severe adverse effects, such as permanent paralysis, from the mercury poisoning. Foetuses of pregnant mothers were affected, suffering developmental problems, leaving a very long legacy (Kudo & Miyahara 1991;Harada 2005). Similar issues arose when salmon and other fish species in the Great Lakes of North America became heavily contaminated with polycyclic aromatic hydrocarbons and PCBs in the middle of the last century, although, in this case, people were not directly killed by ingesting contaminated fish and, in fact, the evidence for the contamination adversely affecting consumers of the fish is not particularly strong (Leatherland 1998).…”

Study on the Leaching of Mercuric Oxide with Thiosulfate Solutions

“…Mercury may undergo complex physical, chemical, and biological transformations in the environment-e.g., the atmospheric transport of Hg 0 , the photochemical oxidation and subsequent deposition of mercury on water and land, and the methylation of Hg 2+ by reducing bacteria in anoxic habitats and its absorption and accumulation by organisms, which results in high mercury concentration in fish and chronic low level exposure to humans through the food chain [7,8]. More than two thousand people were affected and 1043 died due to Minamata Disease caused by mercury pollution from a local chemical plant in Japan in the late 1970s [9].…”