Residual neurologic deficits 30 years after occupational exposure to elemental mercury

A battery of tests of peripheral and central nervous system function was ad ministered to 205 former workers of a large heavy industrial plant, 104 of whom were previously exposed to inorganic mercury. The mean age of those ex amined was 71 years. Exposed subjects had participated in a urine-mercury e xposure monitoring program during the time of operation of a process that r equired the use of mercury and its subsequent cleanup. Mercury exposure had been high (mean peak urine mercury concentration was >600 mu g/l) and had ended 30 years or more prior to the investigation. Peripheral nerve functio n outcomes that were statistically significantly associated with cumulative mercury exposure after controlling for covariates included classification as having peripheral neuropathy, peroneal motor nerve conduction velocity, ulnar motor nerve conduction velocity, and peroneal motor nerve F-wave late ncy. Quantitative assessment of resting tremor was nearly significantly ass ociated with cumulative mercury exposure (p=0.07). Among tests of central n ervous system function, results of the Handeye Coordination test were signi ficantly associated with cumulative mercury exposure after controlling for covariates. Cumulative mercury exposure was not observed to be associated w ith a quantitative measure of dementia or with a number of cognitive neurob ehavioral test outcomes. The statistically significant associations with me rcury exposure were observed in spite of greater mortality among the expose d group than the unexposed group. These results suggest that substantial oc cupational mercury exposure can have long-term adverse effects on the perip heral nervous system detectable decades after cessation of exposure. Such l ong-term adverse effects were not observed for a measure of dementia or oth er measures of cognitive function. (C) 2000 Intox Press, Inc.