CAN TREMOR BE USED TO MEASURE THE EFFECT OF CHRONIC MERCURY EXPOSURE IN HUMAN-SUBJECTS

Clinical and quantitative studies in which tremor was used to evaluate the effect of chronic exposure to organic and inorganic mercury in hu man subjects during the last 20 years were identified in MEDLINE and B IOLOGICAL ABSTRACTS. In the selected studies, methods varied widely by types of transducers used, anatomical locations of tremor testing, ta sks executed by the subjects, types of tremor recorded and durations o f trials. Measurements of tremor in these studies also varied by frequ ency, amplitude, waveform and reproducibility. Typically measures of v ariability were not included. Results obtained depended heavily on the methods and analyses used We suggest that, although many contradictio ns and discrepancies have been noted in these studies tremor can proba bly be used to measure the effect of chronic mercury exposure. This wo uld involve more rigorous and uniform recording procedures and analyse s. Specific suggestions proposed include: realizing the limitations of accelerometric data; considering the effect of weight on the tested l imb; controlling recording conditions; selecting samples more carefull y; recording other physiological variables besides tremor; using tasks and manoeuvres that unmask subclinical abnormalities in tremor; repor ting frequency, amplitude, waveform and variability of tremor; underst anding the limitations of power spectra analysis; separating tremor ch aracteristics according to types of mercury exposure; and considering supraspinal influences that both vision and voluntary movements have o n tremor. (C) 1996 Intox Press, Inc.