Electromagnetic Field Exposure and Amyotrophic Lateral Sclerosis

Sir, Amyotrophic lateral sclerosis (ALS) is a fatal degenerative neurologic disease involving the motor cortex, corticospinal tract, and anterior horn cells of the spinal cord. The cause of ALS remains unknown, We have investigated occupational exposure to electromagnetic field (EMF) in a man, aged 61 years, having ALS. To assess historical exposure to EMF, a Monitor Labs 42A Gauss-meter was used to take spot measurements. An EmdexC personal monitor was used to record the ambient EMF fluctuation over time. A few areas of up to 25 mGs were identified in the clothing plant where the patient had worked. Of interest was a power transformer located on the floor below the patient's desk chair, which produced the highest EMF found in his office. The largest possible exposure was 75 mGs that occurred when his foot rested on or next to the transformer. His first symptom was foot dragging and loss of control of the toes. This occurred following at least 6 years of exposure. Although this is perhaps an isolated event and due entirely to chance, there is recent interest in the possibility that long-term exposure to EMF may induce disease. Therefore, investigation of EMF in the search for the etiology of this uniformly fatal and progressive motor disability may be fruitful.