Although the Chisso Company started the production of acetaldehyde in 1932, it was not until 1956 that an official confirmation of Minamata disease was made. However, Dr. Hosokawa discovered a similar outbreak back in 1953. In addition, investigations by Kumamoto University’s Second Minamata Disease Study Group said that there is a possibility that another outbreak took place in 1942.

The cause of Minamata disease is the methylmercury contaminated wastewater released from a factory in the area. Minamata disease can be contracted by eating seafood polluted by methylmercury.

Because Minamata disease is not an infectious disease spread by a virus or bacteria, it is not contagious. So far there have been no cases reported that show clear hereditary transmission of methylmercury poisoning. However, a report from the NRC (National Research Council) in America says that proof of the genetic influence of methylmercury is inconclusive.

At the time of official confirmation in 1956, according to Hunter-Russell syndrome, the people who had central neurological symptoms such as ataxia, narrowing of visual field, speech disorder, and hearing loss were recognized as patients. In serious cases, patients had consciousness disorders or convulsions and died. However, the existence of patients who did not have all the symptoms was confirmed later. Nowadays the main symptoms of chronic Minamata disease in adults are sensory disorders. In more severe cases additional symptoms like trunk ataxia, upper/lower limb ataxia, narrowing of the visual field and so on are present.

Because it is a question of poisoning there are a great deal of variables involved, which means that the symptoms, disease types, disease patterns, as well as the degree of severity and so on, all of which depend on the differences between individual patients and the length of time they have been exposed to methylmercury, will show up in many different forms.

At one end of the scale there are very severe cases which cause the patient’s death and at the other end of the scale there are mild cases with either some of the signs and symptoms or all of them, but which respond to treatment. In addition, the damage to the central nervous system caused by methylmercury is believed to be affected by the developing neuronal network. So the severity of the symptoms can vary according to the patient’s cognitive and behavioral ability.

There are at present two ways of receiving compensation for the Minamata disease. One way is the Minamata Disease Authorization Application in which the Minamata Disease Authorization Examination Committee authorizes compensation based on the “Law Concerning Compensation for Pollution-Related Health Damage”. After authorization the victim is classified as either A, B or C. Depending on the classification the victim will receive a lump sum varying between \16 million - \18 million as well as an adjustment allowance, medical care allowance, care costs, a nursing allowance and various treatments including acupuncture, moxa cautery, massage and visits to hot springs. At present there are almost no possibilities for patients to be certified under this law.

The other system is the, “Minamata disease Patient’s Record Book”. In this system the patient, if he/she is accepted, is not allowed to apply for any other form of Minamata disease compensation. The victim has to be able to prove residency in the polluted area within the period of time stipulated by the Government and also to have eaten seafood from the polluted area. The certification has to be done by a doctor who has been trained in diagnosing Minamata disease or similar diseases of the nervous system. The doctor has to be able to provide medical certification showing that the victim suffers from four-limb sensory disturbance or general sensory disturbances. The “Minamata disease Patient’s Record Book” system allows for compensation for medical costs, acupuncture and moxa cautery expenses.

There used to be a similar system called the “Medical Record Book” compensation system based on the Special Medical Care system started in 1986. That system ended in 1996 after the court case was settled in 1995 and the compensation of a lump sum of \2.6 million and medical expenses was awarded to each plaintiff.

As of December 31, 2009, the numbers of Minamata disease patients, who have received administrative measures, were as follows,

After the enactment of the “Law Concerning Special Measures for Minamata disease,” the administrative bodies concerned, declared that they would never publicly reveal the number of compensated patients. It is believed that the numbers of compensated patients may be over 50,000. In actual fact there have been a lot of victims, both living and dead, who never applied for official aid or compensation. If we were to add those to the number of patients believed to have Minamata disease, the number of victims would likely be in the region of several hundred thousand.

Methylmercury is absorbed into the body through the intestinal tract and enters the bloodstream. It is carried throughout the body and passes through the blood brain barrier (BBB) and affects parts of the central nervous system such as the cerebrum / the cerebellum. Sensory, motor, intellectual and mental functions can also be affected.

In the adult brain it is believed that the comparatively small brain cells, which exist in the fourth layer of the cerebral cortex and receive sensory information from all parts of the body, are damaged and cause the sensory disorders associated with Minamata disease. In fetal exposure, on the other hand, such selectivity is low and it has been found that the whole cerebrum, cerebellum and brainstem can be damaged.

As well as the central nervous system, it has been found that methylmercury accumulates in the kidneys, but no clear connection between kidney disorders and methylmercury poisoning have been discovered. There do not seem to be any malignant diseases connected with methylmercury.

A fall in the number of male babies born during the time of worst pollution has been reported. But there is some controversy about any connection between methylmercury and the environmental endocrine disrupter effect.

During the acute period, the administration of a mercury chelating agent is said to be effective, but most of the current patients are in the chronic stage, and a mercury chelating agent is not effective. Chronic stage treatments are almost all symptomatic ones. Medical therapy and rehabilitation such as physiotherapy and kinesitherapy are provided.

Because the level of methylmercury pollution in Minamata and surrounding areas is much lower than it was during the period of heavy pollution, the severe symptoms seen among the people exposed to methylmercury during the 1950’s and 1960’s, is unlikely to appear again. However, the relationship between the level of methylmercury and health disorders is not yet clear, we cannot confirm that methylmercury levels today will not influence health detrimentally the future. There may still be undiscovered health effects among people who have been exposed to methylmercury, even if it the exposure level was low.

In 2004, some fish in Minamata Bay were reported to have methylmercury levels higher than the limit set by the Government. In our research, even now, among inhabitants who eat seafood from the adjoining sea, there are some who have hair mercury levels which exceed 10ppm. It is impossible to give a 100% guarantee that it is now safe to eat fish from the bay as even when low concentrations of methylmercury (less than 10ppm) are measured in the hair, there can still be an effect on adults and embryos.

The handling of a patient’s personal information At the Houwakai Medical Corporation’s Kyoritsu Neurology and Rehabilitation Clinic (hereafter, “this clinic”), we handle patients’ personal information and private medical details carefully, and pay close attention to protecting the patients files and information.

Personal information At this clinic, we follow the laws and regulations dealing with the storing of personal data on an electronic retrieval system and the storing of personal data in physical documents. This includes the protection of information contained within our home pages.

Management of personal information At this clinic, we pay very close attention to how will we store a patient’s personal information and protect it against all forms of improper disclosure.

When you report or are consulted about Minamata disease, you will be asked for personal information like your name, address, telephone number, e-mail address and other information. This personal information is necessary to help us document and record information about your case correctly.

Confidentiality of personal information At this clinic, we pay maximum attention to the handling and protection of the personal information of patients. Neither can the personal information nor the private medical details of patients be disclosed to a third party without the consent of the patient himself/herself. Within this clinic however, medical staff involved in a patient’s case will have access to the information. However, we may disclose personal information in the following cases. 1) In the event that a patient commits a criminal act within our premises, we may release that patient’s registered information to a concerned party, such as the police. 2) In cases where the registered information of a patient is demanded by a court of law, a public prosecutor, the police, a legal association or organization acting on behalf of any of these authorities or similar authority, information may be disclosed.

Discontinuance of the utilization of a patient’s personal information When there is a specific request from the information provider himself or herself, we delete the personal information that the person give us and discontinue any further use of it from then on.