Health evaluation and reported symptoms in workers with past occupational exposure to elemental mercury.

Abstract

A comprehensive health evaluation was conducted on 502 workers at the Y-12 plant in Oak Ridge, Tennessee of which approximately half (247) had past exposure to elemental mercury vapor between 1953 and 1966. Extensive urinalysis records were available and a number of exposure indices were generated from these in an attempt to model different aspects of exposure. Selection into the study group was based on an index of cumulative exposure that consisted of the sum of average quarterly mercury urinalyses. Cumulative and peak exposure indices based on workers' average exposure from company work histories were more strongly associated with adverse health effects than corresponding indices based on individual urinary records. Substantial evidence suggested that higher exposed workers were at elevated risk for the development of a mild peripheral neuropathy and sustention tremor. In addition, a small increase in the frequency of mild myelopathies was noted in the mercury-exposed group which was not clearly related to exposure. Reported symptoms of lightheadedness, confused, trouble remembering steps, bothered by clumsiness, and trouble grasping objects were significantly associated with increasing level of elemental mercury (either cumulative or peak). A preliminary evaluation tends to validate the use of symptoms data in epidemiologic surveys. Symptom reports were related to poorer performance on objective tests of psychomotor and other behavioral attributes. An increase in level of the urinary enzyme N-acetyl-B-glucosaminidase was significantly associated with increasing cumulative exposure to elemental mercury even though current urinary mercury was not associated with past exposure. It remains to be seen if the findings of persistent effects associated with elemental mercury exposure in this cohort of older workers can be detected in other cohorts of workers exposed to mercury. It is possible that much of the subtle dysfunction and performance decrement detected in this study was due to an interaction with age and not readily detected in studies on cohorts of younger currently employed workers.