The unfolding mercury disaster
The village of Minamata, located on the west coast of southern Kyushu, was traditionally supported by rice farming and by a cove in the port which allowed the production of salt. All this was well established by the beginning of the twentieth century. Across the bay is Amakusa Island, which produced some coal; there was also a gold mine in the mountains. These materials were brought into Minamata village and wood and mountain products were shipped from the port. Otherwise, Minamata was no different from other villages found throughout the country. (reference)
After World War II, the production of acetaldehyde boomed. The city of Minamata grew along with the expansion of Chisso. Indeed, the city served as a model company town. The penetration of Chisso's influence and that of affiliated companies is shown by several statistics. Between 1956 and the early 1970s the industrial complex occupied 68% of the city's land area and consumed 93% of its water supply. Chisso related businesses accounted for 30% of retail sales, employed 19% of the workforce and commissioned 66% of all the shipping activity.
About the same time, fish began to float in Minamata Bay. Chisso, as it had since 1925, continued to pay indemnity to local fishermen for possible damage to their fishing waters. Also at that time, cats began to exhibit bizarre behavior that sometimes resulted in their falling into the sea and dying, in what residents referred to as "cat suicides."(reference)
In the early 1950's, similar behavior began to appear in humans. People would stumble while walking, not be able to write or button their clothes, have trouble hearing or swallowing, or tremble uncontrollably. In 1956 an apparent epidemic broke out and one can imagine the confusion and fear that was prevalent because no one knew the cause. Was it a viral inflammation of the brain? Was it syphilis? Was it hereditary ataxia, or alcoholism? Was it infectious? The popular names of "cat's-dancing disease" and the "strange disease" convey some of both the mystery and its alienating quality.
By the end of 1956, epidemiological and medical researchers identified the disease as heavy-metal poisoning caused by eating the fish and shellfish of Minamata Bay. Direct evidence that mercury from the Chisso plant was responsible, however, did not emerge until 1959. Dr. Hajimé Hosokawa, in private tests on cats at the Chisso Company Hospital, showed that the plant's acetaldehyde waste water caused the disease symptoms (though the results were not made public). Chisso installed a "cyclator" designed to control the emissions, offered `mimai' (consolation payments) to the patients, and the matter seemed resolved. Nearly 100 patients had been identified, of whom over twenty had died.
However, more patients emerged and children were also born with the "disease." The geographical distribution of cases widened. In 1963, Public Health Service researchers traced the disease to mercury from Chisso. Controversy soon erupted over who was responsible for compensating the victims and supporting their families. It was not until 1970 that a district court ruled that Chisso was to make payments totaling $3.2 million to the original group of patients. Others soon received payment by negotiating directly with Chisso.
Chisso finally stopped production of acetaldehyde in 1968, when an alternative technology for producing plastics was developed. Still, through the 1970's and 80's, new patients continued to surface. In some cases, the symptoms were partial (numbness or tingling in the extremities, for instance, or frequent headaches or the inability to concentrate) and it was hard to determine the exact extent of the mercury's effects.
See also: Amalgamation, Appliances, Chlor-Alkali, Dentistry, Explosives, Iraq poisoning, 'Mad as a Hatter', Mercury, Methylmercury, Minamata, Minamata timeline, Medical uses, Pigmentand organic fungicide production, Toxicology