Before the Fukushima tsunami and near-nuclear meltdown in March, the greatest environmental disaster in Japan, indeed, one of the greatest in the entire world, was Minamata disease, a neurological affliction caused by severe mercury poisoning which can cause limb paralysis, difficulties in walking, mental confusion and death.

It is named after Minamata Bay on the southern island of Kyushu. The Chisso chemical company had been dumping mercury-contaminated waste water in the bay for decades. In the 1950s and 1960s, many people living in the vicinity came down with strange illnesses tied to eating the mercury-contaminated fish caught in the bay.

As a result of the contamination, 1,784 people died and thousands were afflicted with insanity, paralysis, skeletomuscular deformities and the inability to walk. Something like an additional 40,000 uncertified victims have applied for damages under a 2010 law that gives sufferers three years to come forward and establish their claims. Some of them are in their 40s and 50s, which means they were born after Minamata disease was recognized and are claiming that they were actually injured while in the womb.

Minamata disease was first suspected in 1956 and was officially pronounced a pollution-linked disease in 1968. That makes it all sound like ancient history. Yet Minamata disease is extremely relevant, both on its own terms and because it provides lessons, often discouraging ones, about the most current environmental disaster stemming from the multiple nuclear meltdowns.

In March, about a week after the Great East Japan Earthquake, a group of previously unrecognized Minamata victims settled a long-standing damage suit, paving the way to finally end the lengthy struggle to bail out the victims. Under the terms, the chemical company will pay each of more than 2,000 plaintiffs (94 have died) about $25,000 while the prefectural government will cover monthly medical expenses.

The settlement made Toshiyuki Kawakami 86, and his wife, 84, finally eligible to collect damages – 38 years after they originally filed their complaint. "I am relieved that we were recognized while I am still alive,” he said after the settlement was pronounced.

The settlement was especially sweet for Kawakami in that he was one of the leaders of a group who in 2004 won a landmark ruling from Japan’s Supreme Court, holding the national and prefectural governments liable for the spread of the disease. Throughout most of the 1960s, ‘70s and ‘80s, the government had denied any culpability and left it to Chisso to handle any compensation payments alone.

The executives at Tokyo Electric Power Co. (Tepco), owner of the four disabled nuclear power plants at Fukushima, must look on the Chisso Company and see themselves 50 years from now. Yet Tepco faces much greater demands for compensation, although it does have larger resources, now including government backing, to pay them down,

Chisso is a private company in a competitive field of liquid crystal displays and other modern chemicals. Tepco is in a different league in that it enjoys a major regional monopoly in selling electricity. Still, like Chisso, it will be obligated to pay out compensation for the next 50 to 60 years or more.

Tepco’s share price plunged after the March 11 earthquake and tsunami as investors were understandably spooked about the prospects of the company paying out large sums in compensation to those impacted, by the radiation leaks.

Shares did rebound when, a couple weeks ago, the Japanese parliament passed a law to help the company shoulder some of the damage demands, which are likely to run into the trillions of yen. It sets up a mechanism to provide Tepco with some assistance if the utility cannot meet the payment demands. But Tepco still bears the main burden for making payments.

The government chose not to place any cap on damages, which leaves them open-ended, meaning the liabilities are likely to be a drag on the company for years if not decades to come, much like Chisso, which over the years has booked about $3 billion in cumulative losses from the mercury poisoning debacle.

The government is navigating a fine line, not wanting to shift the entire burden on to the taxpayer, but also mindful that Tepco is the sole supplier of electricity to the world’s largest city. Moreover, it would not be too hard for future lawsuits to find the government culpable or inadequate oversight of the afflicted nuclear power plants.

Chisso chose not to file for bankruptcy or seek to nationalize its liabilities (two options that have been bruited for Tepco but discarded for now). Instead, Chisso's creditors waived some of their loans or accepted delayed payments. The price Chisso paid for not going bankrupt was a negative net worth that has lingered for the past 50 years.

Even so, Chisso is still in business. It even issues shares of stock, although on the unlisted Green Sheet Market rather than the regular Tokyo Stock Exchange. Latest figures valued the company at 13 yen (about one US cent) a share with a market capitalization of about $80 million.

Earlier this year, Chisso split itself into two main companies. One, a holding company, inherits all of the liabilities stemming from the mercury poisoning. Another company, called the JNC Corp, will handle the business end of things. Eventually it will go public, and the profits the holding company earns from stock sales or dividends will be used to pay damages.

It is likely that Tepco will share with Chisso the difficulty of identifying legitimate future claims. Of course, it may be relatively easy to tote up the economic losses stemming from the nuclear disaster, but the cumulative effects of mercury poisoning and long term effects of radiation are similarly difficult to define, especially as symptoms tend to develop more in advanced age..

Said one doctor involved in the Minamata disease claims, it may be necessary to make a list now of those who have been affected with radiation at Fukushima, so that the authorities can keep track of their health conditions over a long period of time. That is one lesson of Minamata for Fukushima.