Pollution Past and Present: Minamata disease

Minamata is a peaceful fishing region on the west coast of Kyūshū in Japan. However, fragments of a tragic history are threaded throughout this city that was once plagued by a mysterious disease.

In early 1956, residents of Minamata Bay began noticing strange displays of behaviour from the local cats. The felines would drool excessively, spin in erratic circles, and sometimes throw themselves into the bay to drown. From these observations, the disease was coined ‘Dancing Cat Syndrome’ in its early days. However, shortly after, the human residents of Miniamata Bay began experiencing bizarre symptoms, too. 

Most commonly affected were local fishermen and their families, though many people within the region ultimately fell victim to the symptoms. The disease often began with numbnesss and tremors in the extremities, followed by gradually worsening convulsions, sensory loss, and loss of motor control. In the most severe cases, victims would descend into madness or fall into mortal comas mere weeks after the initial onset of symptoms. Oftentimes, women who developed Minamata Disease during pregnancy would give birth to children with physical and learning disabilities. Yet with the cause of this disease initially remaining a mystery to its victims, the illness was simply named ‘Minamata Disease’. 

In November 1956, Kumamoto University reported that exposure to organic mercury — methylmercury — was the cause of this new and concerning disease. What they couldn’t decipher, however, was how the residents of Minamata bay had been exposed to such poisonous levels of methylmercury. 

With our modern understanding of pollution, it is not too difficult to deduce the source of mercury that led to the sickness experienced by thousands — the methylmercury was built up within the seafood harvested, consumed, and traded in the local area. A typical Minamata diet consisted of high volumes of seafood; local circles even encouraged pregnant women to consume higher volumes of protein-rich fish during pregnancy. Yet, unbeknownst to these locals, the fish in the Minamata region contained dangerously high levels of mercury. But why? 

Following the report released by Kumamoto University in 1956, attention turned to the number one suspect — a nearby chemical factory named Chisso. One of the main chemical products manufactured at Chisso was octanol, which would be sold to other companies to make PVC. In order to create octanol, Chisso required acetaldehyde, which was produced using mercury as a catalyst. Following accusations, Chisso denied any irresponsible disposal of mercury byproducts. 

Despite this public statement, individuals working within Chisso were not so certain of their innocence. Whilst Chisso was under the belief that organic mercury broke down rapidly in the environment, one worker in particular doubted this. Shiode Chuji, who was in charge of production experiments at Chisso, had witnessed the methylmercury leaking within the factory and had concerns about the liquid escaping into the nearby oceans. He wrote a report voicing these concerns, yet this was ultimately ignored by his colleagues. 

Meanwhile, Chisso’s in-house hospital began conducting secret experiments to assess the solidarity of the claims made against them. They allowed cats to drink from samples of the factory’s waste water, rapidly observing the onset of symptoms associated with ‘Dancing Cat Syndrome’. Yet, Chisso still refused to admit responsibility for Minamata Disease. 

Throughout the 1960s, people continued to develop Minamata Disease whilst Chisso denied responsibility. Yet, in 1961, Chisso engineer Shun’ichi Ishihara analysed the wastewater within the factory to discover methylercury within it. Discovering this, Ishihara continued experimenting until he had a strong link between the factory, wastewater mercury and Minamata disease. When presented to Chisso management, they remained indifferent and the research was never published. 

After over a decade of suffering, the people of Minamata eventually filed a corporate neglegence lawsuit against Chisso in 1969. Once a four year trial came to an end, the people of Minamata had won and Chisso was required to compensate the victims of the disease it had caused. Though, sadly, the effects of Minamata disease continue to be felt to this day, with victims still living with the disabilities caused by the unjust exposure to mercury and many more facing a perpetual legal battle to be recognised as official Minamata disease victims. 

The seas surrounding Minamata Bay have been declared safe from mercury oncemore. However, some of the locals have doubts and choose to avoid fishing in the waters that were once heavily contaminated with merthylmercury. Minamata’s damaged dignity is slowly being rebuilt with efforts to improve its landscape, such as through the development of new ecoparks. Yet, these ecoparks sit atop sealed deposits of mercury, causing locals to fear that an earquake or tsunami could dislodge this contaminated soil and lead to another outbreak of mercury poisoning. Therefore, whilst many believe that Minamata has restored its status as a desirable safehaven, others remain unsure that Minamata can be considered truly safe from the lasting effects of mercury.