At the beginning of 2002, unusual symptoms appeared in Ryuji, a 6-month-old boy living in a small town in Ibaraki Prefecture north of Tokyo. The infant could not sit up or eat properly. With a high fever and trembling hands, he was diagnosed with an unknown cause of cerebral palsy.

Ryuji's family had moved into a rental house in Kamisu in October 2001. However, immediately after moving in, all four members of the family began to experience unexplained physical ailments.

"I remember that residents, including my family, were advised not to use the water because hazardous substances had been detected," said Ryuji's mother, Miyuki Aotsuka, 48. Ryuji's older sister Rina also began feeling ill and could not attend school, his mother said.

"The local police came to our house around 10 p.m. They had received a call reporting arsenic poisoning from the nearby water. The police asked me about the arsenic as if I were a suspect in an alleged poisoning of the water supply," said Ryuji's father Shinichi.

He said he later learned from news reports that the arsenic had leaked from a site where it had been dumped after originally being produced for use in the former Imperial Japanese Army's poison gas program.

In what is known as the Kamisu Arsenic Case, poison leaking from the buried chemicals contaminated the surrounding well water. Nearby residents who ingested the water experienced neurological symptoms such as numbness, dizziness and tremors in their limbs.

The Aotsuka family is especially grateful to Tsuyoshi Ogata, head of the local health center, for researching the water supply and helping residents apply for a special medication book that allows them to receive free medical care.

Ogata was assigned to the Itako Health Center in 2003 amid residents' concerns about the water. A University of Tokyo medical school graduate, Ogata had been working on Minamata disease, the neurological syndrome caused by major industrial pollution in Minamata, Kumamoto Prefecture.

"Several residents were experiencing unusual symptoms. I thought the problem was water, like the Minamata case I was familiar with. History sometimes repeats itself, so I was grateful to learn lessons from the past," Ogata said. He added that there was no distinct department handling health injuries from underground water since it was a natural resource.

"I knew someone had to work on this, even if it may be outside our jurisdiction," Ogata added.

A water quality survey found that arsenic levels in the well water that the family used for drinking were 450 times higher than the environmental standard.

Analysis revealed the poison to be an organic arsenic compound, specifically diphenylarsenic acid, which does not exist in nature. Further investigation revealed that diphenylarsenic acid had been buried in concrete in an empty lot approximately 90 meters from Aotsuka's home.