Detection of hand tremor in workers exposed to mercury vapor: a comparative study of three methods.

Hand tremor measurement was evaluated in a group of 54 male workers (mean age 38.5 years) exposed to mercury vapor (average duration of exposure 7.7 years) using an accelerometer test and two psychomotor tests (eye-hand coordination and hand steadiness). The results were compared with those obtained in a well-matched control group of 48 workers. The intensity of current mercury vapor exposure was rather moderate as reflected by the mean (geometric) levels of mercury in blood (2.4 micrograms/dl) and in urine (63 micrograms/g creatinine). The hand steadiness test and eye-hand coordination test revealed preclinical alterations in postural and intentional tremor, whereas the changes evidenced by the accelerometer test were not statistically significant. Furthermore the practical advantage of the psychomotor tests over the accelerometer test makes them most appropriate for the early detection of mercury-induced hand tremor. The present study also suggests that young adults (less than 21 years) may be more susceptible to the neurotoxic effect of mercury vapor.