Acetaldehyde reacts with acetic anhydride in order to produce ethylidene diacetate, which is heated to produce vinyl acetate. Chisso Corporation produced acetaldehyde using water, acetylene, mercury(II) sulfate as a catalyst and manganese dioxide or since August 1951, ferric sulfide as a co-catalyst. The cause of this contamination in Minamata bay was then traced back to Chisso Corporation's dumping of methylmercury into Minamata Bay. Most patients exhibited combinations of symptoms and did not show all symptoms. decrease in communication skills (slurred speech).The methylmercury inside the contaminated fish attacked the affected patient's central nervous system, which caused a variety of symptoms. After an extensive investigation, the Minamata disease was identified as a heavy metal poisoning, specifically methylmercury poisoning, transmitted by the ingestion of contaminated fish from Minamata Bay. Many of the earliest patients became insane from the symptoms and in some cases died within a month of being affected. The first report of Minamata disease originated in Minamata in Kumamoto Prefecture in the year 1956. This meant that they had to ensure the poisoned land was returned to a safe and cultivable state. Mitsui Mining was also obliged to pay recovery costs for the land. Mitsui Mining formally admitted that itai-itai disease was caused by their discharge of cadmium into the Jinzū River. Residents won this lawsuit and began to conduct negotiations. Residents of the surrounding area that were harmed by this disease filed a lawsuit against Mitsui Mining & Smelting Company in 1968. Most people with itai-itai disease were confined to bed because walking caused severe pain. bone fractures from mild traumas or activities (e.g., coughing or walking).However, as the disease progresses symptoms include: The first symptoms were spine and leg pain. Any person who drank that water or ate food that was grown with the contaminated water, such as rice, would be likely to show signs of itai-itai disease. The cadmium poisoned the river, thus poisoning locals' source of water. Mitsui Mining began to discharge cadmium into the Jinzū River in 1910. The source of cadmium was discovered to be from Mitsui Mining and Smelting Company. The cause of itai-itai disease was determined to be cadmium poisoning in the drinking water from the Jinzū River basin. This disease was given the name 'itai-itai' because this was the phrase affected people would frequently cry out it translates into 'it-hurts it-hurts disease'. Itai-itai disease first occurred in 1912 within Toyama Prefecture. 3.3 Aftermath of Niigata Minamata disease.3.1 Symptoms of Niigata Minamata disease.These cases also set precedents for private tort law and civil law in issues of compensation for technology-related mass damage which continue to have repercussions in legal cases in Japan today. The first occurred in 1912, and the other three occurred in the 1950s and 1960s.ĭespite the moniker of 'four' becoming the prominent way to refer to the events, Minamata disease and Niigata Minamata disease were the same pollution disease spread by the same poison, just in different locations.ĭue to lawsuits, publicity, and other actions against the corporations responsible for the pollution, as well as the creation of the Environmental Agency in 1971, increased public awareness, and changes in industrial practices, the incidence of these kinds of diseases declined after the 1970s. The four big pollution diseases of Japan ( 四大公害病, yondai kōgai-byō) were a group of man-made diseases all caused by environmental pollution due to improper handling of industrial wastes by Japanese corporations.

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