In 1908 Shin Nihon Chisso Hiryo (New Japan Nitrogenous Fertilizer Co., whose name was changed in 1956 to the Chisso Corporation) first opened their chemical factory in the Minamata area of the Kumamoto Prefecture. 

The Chisso Corporation began with producing fertilizers, but quickly took over the area and helped greatly expand Japan’s chemical industry. They held so much sway over the economy of the area that at its peak, the Chisso Corporation held over half the tax revenue of Minamata City and the company (and its subsidiaries) helped create a quarter of all jobs in Minamata. It was even dubbed a “castle town” for Chisso, according to Boston University, “ in reference to the capital cities of feudal lords who ruled Japan during the Edo period.” To further the “feudal lords” metaphor, Chisso became so intrinsic to the community that a former factory director served as mayor.

Minamata’s booming economy—especially following World War II—also led to a booming population. Before the Chisso Corporation opened its doors in the early 1900s, the village’s population was just 12,040. By 1949, Minamata was renamed a city and had 42,270 people living there. Just before the disease was noticed in 1956, the city had up to 50,461 people living there.

But the Chisso Corporation’s problems didn’t just begin in 1956. They were the leading chemical manufacturer in Japan, producing chemicals such as acetylene, vinyl chloride and octanol. 

Unfortunately like most large factories of the time, they didn’t properly store their waste products, opting instead to dump their waste water directly into the Minamata Harbor. This led to unchecked health and environmental problems in the area decades before the Minamata Disaster. 

But the catalytic change that turned the Chisso corporation’s wastewater from unsafe to deadly, occurred when they began producing acetaldehyde with an inorganic mercury catalyst. The acetaldehyde then produced acetic acid and plasticizers (chemicals added to make a substance flexible and stretchable), and through this production process the original inorganic mercury would become a methylmercury byproduct in the Minamata Bay that “was discharged into the sea until 1966 virtually without treatment.” 

Mercury itself has been well-known throughout the centuries to have harmful effects for humans. The “quicksilver” metal was used for antiquities (such as clock-making), hat making (the well-known neurological effects of mercury on the brain coined the phrase “mad as a hatter”), and even as a constituent for various medications. 

Until environmental disasters like this and the mercury poisoning of Saint Lake on the Canadian border, it was commonly believed that inorganic mercury compounds were relatively insoluble. 

Although regular inorganic mercury isn’t soluble, anaerobic bacteria (bacteria that doesn’t require oxygen) in the water combined with the mercury waste dumped into the bay to form methylmercury compounds… Compounds of the toxin that would now be bioavailable for plants to absorb. 

As a result, in the Minamata bay area scientists found high concentrations of methylmercury in the fish fatty tissue through the processes of bioaccumulation and biomagnification (139). This meant that the longer the fish were exposed to the methylmercury poisoning in the water, the higher the concentration of toxicity in their bodies, and the higher the concentration of toxins as they went up the food chain. The figure below shows how the biomagnification of methylmercury occurs in organisms.

Unfortunately for the people of Minamata, their fisherman’s diet carried the toxic methylmercury poisoning the fish straight into the bloodstream —about 90% of exposed methylmercury directly absorbs into the bloodstream. Through a person’s hair follicles, scientists can determine the amount of mercury a person has been exposed to. Someone who hasn’t experienced any sort of mercury poisoning usually has a level of about 2 ppm. At about 50 ppm, human beings can begin to experience nerve damage. The fish and other marine life in Minamata Bay had between 5.61 and 35.7 ppm, and the hair of patients and their families also had high levels of mercury contamination—the highest level found at 705 ppm. This is a table showing the levels of mercury contamination found in an average Minamata citizen who began experiencing neurological symptoms.

Average daily intake	3-7 μg/kg0.003-0.007 ppm
Body burden	15-35mg（50kg weight)
Total mercury concentration in blood	20-50μg/100ml0.2-0.5 ppm
Total mercury concentration in hair	50-125μg/g50-125 ppm

When it does enter the bloodstream, it primarily targets the central nervous system and the brain; causing psychiatric troubles, paresthesia (tingling or numbness without cause), hearing difficulties, blindness, seizures, ataxia (loss of motor control) and sometimes death.

These neurological effects didn’t just affect the victims of methylmercury exposure either. Although the placental barrier has usually been seen as a powerful protection against toxins (meaning that pregnant women exposed to a certain toxin couldn’t pass it down to their fetus), various studies found that the placenta of pregnant women allowed the methylmercury inside. By disguising itself as methionine, an essential amino acid for proteins, and attaching to cysteine (another amino acid), methylmercury could severely affect the fetus, causing the child to be born with mental retardation, deformed limbs, poor reflexes, slow growth and poor nutrition.

But back in 1956, the people of Minamata had no idea the fish they ate were contaminated with methylmercury. At first, they noticed the odd behaviors of animals, particularly cats. Citizens would watch as the local cats would spasm uncontrollably, then leap into the bay. 

While felines had the most infamous symptoms, often dubbed the “dancing cat disease”,  Boston University described the effects the disease had on other creatures in the environment; “Crows had fallen from the sky, seaweed no longer grew on the sea bed and fish floated dead on the surface of the sea.”

As more and more people fell ill, citizens became paranoid of one another. While a genetic cause was quickly ruled out due to the fact the disease occurred in various unrelated subjects, scientists were unable to rule out an infectious agent as an explanation for the pandemic. In a severe instance, 8 of the 11 members of a family were afflicted, and the vast majority of cases occurred with the fishing families living around the coast. Because of the suspected contagiousness of the disease, families who fell ill were isolated and their homes became disinfected. The paranoia of falling ill combined with the social isolation caused many healthy residents to discriminate against victims of the disease. Overall, 1,784 people have died of Minamata Disease as of March 2001.

The Chisso corporation finally began cleanup in 1968, but people—beginning with a young girl in April of 1956, shortly followed by her younger sister— began experiencing symptoms over a decade earlier. Kumamoto University even figured out the cause of the disease to be heavy metal poisoning that first year, and authorities warned people against eating seafood from Minamata Bay… Although they didn’t ban consumption until 1959, and moreover, according to the “Critical Appraisal of the 1977 Diagnostic Criteria for Minamata Disease”: “because the Minamata disease incident was a case of food poisoning, active surveillance should have been conducted according to the Food Sanitation Act, as was the case for other food poisoning outbreaks in Japan. Thus, the situation in Minamata is illegal.” 

This lack of action and continuous denial of issues only got solved in a Supreme Court decision in October 2004, where the central government and the Kumamoto Prefectural government were finally held responsible for all inaction after January 1960, and that the plaintiffs (victims of the disaster) should receive further monetary compensation for this neglect.  

There were multiple reasons as to why the Chisso corporation didn’t stop the production of acetaldehyde using a mercury catalyst. In those first couple years, several studies had failed to confidently find a point source of pollution (besides the connection to seafood), and they failed to recognize the symptoms of severe methylmercury poisoning. At various times, different scientists from the Japan Chemical Industry Association claimed that the disease was caused by: explosives dumped during WWII, manganese, selenium, thallium and copper. They briefly suspected heavy metal poisoning and then they finally reviewed methylmercury.

A big reason why Chisso didn’t stop dumping their methylmercury wastewater once they did discover the cause was because Chisso tried as much as possible to hide the severity of the disease and to give victims as little financial compensation as possible. Despite the tragedy beginning over 50 years ago, to this day, the Chisso corporation has multiple lawsuits spanning decades against it. 

The Chisso Corporation and the Japanese government wanted to deny accountability throughout this whole process. According to the Business and Human Rights Resource Center (and the Japanese Supreme Court), the Japanese government “proposed a settlement plan to those who had not been certified with Minamata disease in exchange for them dropping all related litigation.” Basically, the Japanese government tried to buy out the victims in exchange for not continuing to press charges. Many settled for this, with individuals being paid between ¥2.6 million and ¥2.1 million in exchange for dropping their lawsuits.

Although over 20,000 people have tried to receive compensation for the disaster, only 2,265 have been certified as victims (as of March 2001), with each of those people receiving between ¥16 million and ¥18 million. 

Sadly, a similar epidemic happened not too far from Minamata just a few short years later in 1965— this time with the Showa Denko Corporation in the Niigata prefecture. This is a map showing the areas affected by mercury poisoning.

Photojournalist and Green Action Japan founder Aileen Mioko Smith says in a recent interview with the Japan Times that “People are always saying Minamata’s over but it isn’t because citizens continue to suffer and lawsuits are ongoing. The plaintiffs are people in their early 60s but what we’re actually talking about is kids who haven’t been recognized more than half a century after their bodies were contaminated.”

Smith continues by saying, “they were brainwashed into thinking the symptoms they experienced had nothing to do with mercury poisoning as they thought it only affected their parents and grandparents. Eventually came the realization that they were poisoned, too, yet the government just wants to use its power to cut them off until they all die.”

Aileen Mioko Smith and her husband W. Eugene Smith traveled to Japan while working for Life magazine during the peak of the disaster, to document and expose the Chisso corporation’s destruction to human bodies and to draw attention to the victims of mercury poisoning.

One such unfortunate victim he photographed was one of the children born with methylmercury poisoning and her mother. 

Tomoko Uemara in Her Bath (1971) by W. Eugene Smith

Although Tomoko died in 1977 at 21 years old, the intimate and jarring photograph Gene took of the mother and daughter became internationally famous, raising awareness about the atrocities of the disease and the Chisso corporation’s corruption. 

This photograph became well known, but not without its drawbacks— for both the family and the Smiths, who were threatened by citizens whose livelihoods depended on the factory.

 In 1972, goons who worked for the Chisso corporation came and attacked the couple, threatening them to “get out or else”. Gene Smith had already sustained a few injuries from photographing WWII and experiencing a couple of plane crashes, but the blows he took that day from the Chisso workers shattered vertebrae in his back. His wife Aileen recalls that “‘the nerve from his finger to his neck was crushed’ causing temporary blindness in one eye as well as blackouts when he raised his arm. ‘It affected him immensely.’”

An article titled “Minamata Disease and Environmental Governance” sums up the ultimate failure of the Minamata Disaster: “As a whole, the history of the two incidences of Minamata disease shows a lack of environmental governance in Japanese society. Effective environmental governance is the ability to produce adequate solutions to a variety of environmental problems.”

In 1970, the Water Pollution Control Law began, which forced the companies to regulate the amount of toxic substances like Mercury and Cadmium are discharged in the water. The environmental cleanup had cost the Chisso corporation 30.5 billion yen, because there was still a high concentration of methylmercury in the soil so they had to dredge the bottom of the river sediment.

Minamata Disease doesn’t just exist in Japan either. Despite knowing the severity of ramifications, corporations all around the world still improperly dispose of mercury into large bodies of water. A Minamata Convention on Mercury was established in 2013 to try and protect the environment from anthropogenic releases of mercury, halting manufacturing, import and export of various mercury compounds and products, which gained traction in 2017. Even still, mercury emissions from human causation continues to rise—over 20 percent in the last five years— despite knowing the tragedies that could happen. Yoichi Tani, a leading spokesperson for the Minamata Convention on Mercury, says that although 123 countries have signed the treaty, “we need every country to ratify the treaty, impose stricter regulations, and prohibit the mining and discharge of mercury.”

Despite the deep tragedy of the Minamata Disease, the city itself has transformed and looks towards a brighter future. After the environmental restoration of the area from the 70s to 90s, and a few new environmental policies—such as a limit of .4 ppm of mercury and .3 ppm of methylmercury— allowed in fish. This policy still continues, but now it doesn’t apply to tuna, swordfish and freshwater fish—Minamata has been considered an eco-town since 2001. 

They have a variety of sustainable initiatives such as a strict garbage and recycling classification program, encouraging positive environmental changes such as farming, fishing,  saving energy and reducing waste, to help turn the city’s legacy from negative to positive. 

This idea actually dates back to 1992, with the government calling for ‘Moyai Naoshi’ (meaning ‘Repairing social bonds’), to try and eradicate the deep social divisions between victims of the disaster and other Minamata citizens—divisions first rooted in the claims that the disease was contagious. Along similar lines, in the same year they had their first memorial service for victims and in 1988 they established a Minamata Disease Municipal Museum, which included testimonials from people struggling with the toxin, with one of the victims saying “If things remain as they are now, we will die to no purpose”. They encourage people to think critically at the museum, not just to remember the past tragedy but to learn from its mistakes and failures on all fronts.

Just outside the center of Minamata, a Declaration of Construction of Eco-City model was established in 1992, and this declaration created an eco town industrial park, which allows them to recycle, “used bottles, television sets, air conditioners, refrigerators, tires, used oil, plastics and sewage,” according to one Japan guide. In 1999 it received an international standards certification for environmental waste policies. 

The city now has about half the population it did at its peak in 1956, at just around 25,000 people.