[Amyotrophic lateral sclerosis and mercury--preliminary report].

The mercury and selenium content in the hair of 13 ALS cases was studied by neutron activation analysis. The total mercury content of the hair was 3.70 +/- 2.73 ppm (mean +/- standard deviation) in the ALS patients as a whole, 4.46 +/- 3.16 ppm in the ALS patients from the middle of Kii Peninsula, and 2.49 +/- 1.38 ppm in the ALS patients from other region. As the comparison, mercury content was 2.43 +/- 0.79 ppm in the patients with Parkinsonism, and 2.10 +/- 1.13 ppm in the patients with multiple sclerosis (MS). The selenium content of the hair was 0.36 +/- 0.35 ppm for all ALS patients as a whole, 0.45 +/- 0.25 ppm in the ALS patients from the middle of the Kii Peninsula, and 0.21 +/- 0.47 ppm in the ALS from other region. There were no cases with higher values than mean values of control group, except one case from other regions. It is well known that the selenium decreases the toxicity of mercury in the human body. From these data mercury with low content of selenium might be one of the environmental factors which are thought to be involved in producing of ALS.