[citation needed] The pollution at Toroku dates back to 1690 according to A Table of Public Hazards of Japan[1] Seven patients were examined extensively at Kumamoto University, and they were diagnosed as having chronic arsenic poisoning due to pollution, in a report published in 1973.
[2] The same team increased the number of patients to 48 in 1976, while Hotta and his co-workers made extensive studies of the pollution.
[3] Nakamura et al. characterized the condition by pigmentation which is either macular or diffuse, appearing both in covered and exposed areas.
The environmental agency first indicated the skin and ENT findings of nasal scar or septum defect as necessary symptoms for the Toroku Pollution.
In addition to the skin and ENT findings, neuritis was added as a criterion of chronic arsenic poisoning.