[A clinical evaluation of the inorganic mercurialism--its pathogenic relation to amyotrophic lateral sclerosis]

The pathogenic relation of chronic mercurialism and amyotrophic lateral sclerosis (ALS) was evaluated clinically on 83 ex-mercury workers who were poisoned or exposed to mercury vapor about 18 years ago at one of the biggest mercury mines in Hokkaido, as well as on the causes of 65 expired workers in the cohort. The 83 ex-mercury workers were subdivided into two groups according to severity of mercury poisoning: 31 ex-workers who had been hospitalized for treatment of mercury poisoning and the remaining 52 ex-workers severely exposed to mercury vapor but not hospitalized. Neurologic examinations and measurements of mercury contents in the blood, urine, and hair samples in the 83 cases, failed to disclose any pathogenicity of mercury to ALS. Among these 148 including the 65 deceased cases, no ALS cases were found. Further clinical and epidemiological studies should be required on mercury poisoning as one of the risk factors in the development of ALS, especially in relation to selenium.