Minamata Disease is a sobering reminder of the dangers of unregulated industries in modern times, a purely human-created disease. It was first seen in 1956 in the children living in Minamata City on the coast of Japan’s southern island of Kyūshū. Medically it’s a severe neurological syndrome with symptoms including loss of muscle control and weakness, loss of feeling in hands and feet, tunnel vision, loss of hearing, and speech abnormalities. Within a few weeks of onset, extreme cases tragically end with paralysis, insanity, convulsions and eventually death. In pregnant women, it can also lead to birth defects.
But what exactly did humans do to create such a terrible disease?
We have to go back over century to 1908 when the Japanese Chisso Corporation opened a factory in Minamata. First manufacturing fertilizers, the company saw more profit in the chemical industry. So in 1932, Chisso started producing acetaldehyde at its Minamata plant. By 1951, production was up to a whopping 6,000 tons a year. The process unfortunately lead to the production of highly toxic methyl mercury as a waste product. As is the case in such large-scale plants, they produced large quantities of chemical wastewater. Chisso’s solution was to simply dump the wastes, untreated, directly into the surrounding Minamata Bay. They did this for decades until 1968!
The poisonous methyl mercury slowly bioaccumulated in the fish and shellfish living in Minamata Bay and the surrounding Shiranui Sea. Inevitably, Chisso’s pollutants had an environmental impact. Fisheries were damaged with reduced catches. In response to lawsuits, Chisso reached a compensation agreement with the fishery cooperative in 1943. While that was good, the population of Minamata still relied heavily on the bay for a substantial part of their diet. So when fished and eaten by the locals over the years, it resulted in mercury poisoning.
The first case of what would be called Minamata Disease was recorded in 1956. A 5 year-old girl was brought to the Chisso factory hospital. The doctors there were puzzled by her odd symptoms which included convulsions, difficulty walking and slurred speech. Two days later, her younger sister also began exhibiting the same symptoms and was hospitalized as well. The girls’ mother then told the doctors that her neighbor’s daughter was also sick!
After the city conducted a house-to-house check, 8 more patients were found and hospitalized. By May, the hospital’s director officially reported an epidemic of an unknown illness of the central nervous system, calling it Minamata Disease.
Because the disease was confined to Minamata, they suspected it was contagious, quarantining all the patients.
Unfortunately, this only led to the fear and stigma towards the victim’s families from their own community. As the investigation continued, the doctors heard alarming stories of the strange behavior of animals as well. For several years, cats had been convulsing, ‘going mad’ and dying. Locals called it the “dancing cat disease” due to their odd seizures. Crows often fell from the sky and died, seaweed no longer grew in the bay, and hundreds of fish routinely floated dead on the surface of the Shiranui Sea every day.
Researchers from the Kumamoto School of Medicine flocked to Minamata to investigate. Slowly, a more complete picture of the disease was revealed. It began with severe headaches and a loss of sensation and numbness in patient’s hands and feet. They became unable to grasp cups or simply fasten buttons. Then they could not walk without stumbling, their voices changed to an odd pitch. Finally they had difficulties seeing, hearing, tasting and even swallowing. The symptoms quickly worsened and were ultimately followed by severe convulsions, coma and eventual death.
By the end of 1956, 40 people had been hospitalized, 14 of whom eventually died: a shocking mortality rate of 37%. Researchers then began to focus on what could be the cause of the strange disease. Epidemiologists realized that the victims were all clustered in fishing districts along the shores of Minamata Bay. The staple food of those families was mainly fish and shellfish caught from the sea. The local cats and dogs tended to eat scraps from family tables and died with symptoms similar to humans.
This led the researchers to deduce the outbreak was caused by heavy metal food poisoning.
The Chisso plant’s wastewater was immediately suspected as the source. The company’s own data showed that its wastewater contained heavy metals like lead, mercury, and arsenic in high enough concentrations to cause serious environmental damage. Throughout the next 2 years, many theories were proposed, until a British neurologist Douglas McAlpine realized that Minamata Disease closely resembled mercury poisoning.
In 1959, the mercury in Minamata Bay was finally measured. The results shocked the researchers – 2 kg mercury per ton of sediment. Large quantities of mercury were detected in fish, shellfish and the sediment from the bottom of the bay. The highest concentrations centered near the point where the Chisso wastewater canal entered the bay, clearly identifying the factory as the source.
Now, Chisso had always been a boon to the local economy. Over half of Minamata’s tax revenue came from Chisso and its employees. And the company was responsible for supplying over a quarter of all jobs in the city. This fact, combined with the lack of other industries in the area, meant that Chisso had great power and influence in Minamata’s city government. One plant director had even been mayor.
Even after Chisso was identified as the culprit, it did not stop production or dumping for 9 more years, until 1968.
Researchers collected hair samples from the victims and the general Minamata population. In patients, the average mercury level recorded was 705 ppm (parts per million), indicating heavy exposure. In healthy residents, the level was 191 ppm, compared to an average “safe” level of 4 ppm for the rest of Japan.
In 1959, the Ministry of Health and Welfare published its results: Minamata disease is a poisoning disease that affects the central nervous system, caused by the consumption of fish and shellfish living in Minamata Bay and its surrounding sea, the causative agent being organic mercury. The disease is not contagious or transmitted genetically. There is no cure.
The contaminated sludge in Minamata Bay was dealt with partly by land reclamation and partly by dredging at a cost of 49 billion yen over the next 14 years. Ironically, Chisso set up a subsidiary to reclaim the mercury recovered from the sludge and sell it on the open market! Minamata Disease broke out again in 1965, along the banks of the Agano River in Niigata. The polluting factory this time was owned by Showa Denko.
2,265 victims have been officially recognized in Minimata. In 1971, American photojournalist Eugene Smith spent 2 years documenting the effects of Minamata disease in a book, bringing worldwide attention to the tragedy. Finally in 1973, over 17,000 Minamata residents finally received financial compensation from Chisso amounting to 86 million (in US dollars).
The Governor of Kumamoto declared Minamata Bay safe in 1997, allowing fishing again. In 2004, 48 years later, Chisso was finally ordered by the Japanese government to pay for the clean up of its contamination. As you can imagine, additional lawsuits and compensation claims continue to this day.
In 2016, Japan ratified the Minamata Convention on Mercury, a global treaty to reduce mercury emissions. Those children who survived the disease are now in their sixties, continuing to receive regular treatment to this day. All along, their greatest wish was simply to not be ostracized by their own community. Even after it was determined that mercury was the cause, and the disease was not contagious, victims were still reviled as threats to Chisso and thus their economic way of life in Minamata.
A movie titled, Minamata, was released in 2021, starring actor Johnny Depp as photojournalist Eugene Smith.
So what were the hard lessons of Minamata and Chisso? Harder lessons were still to be learned in further industrial disasters like Bhopal, India in 1984 and Chernobyl, Ukraine in 1986. But for one, it teaches us that we human beings, in our endless quest for profit above people and all else, can be both the victims and the perpetrators of its consequences.