Occupational mercury exposure in association with prevalence of multiple sclerosis and tremor among US dentists

Abstract

BackgroundThe effects of chronic occupational exposure to elemental mercury (Hg0) are largely unknown. The objective was to evaluate the association of occupational Hg0 exposure with multiple sclerosis (MS) and tremor. MethodsThe study included 13,906 dentists who attended the American Dental Association’s annual meeting over 24 years (1986-2007 and 2011-2012). Participants reported MS and tremor and provided urine specimens for Hg0 analysis. The authors estimated mean Hg0 exposures over time and used logistic regression to estimate the associations of 3 Hg0 exposure measures with MS or tremor. ResultsAmong participants, 0.18% reported MS and 1.24% reported tremor. Hg0 exposure was not associated with MS (odds ratio [OR] per 191 micrograms per liter in cumulative Hg0 exposure, 0.85; 95% confidence interval [CI], 0.39-1.85). Increased prevalent risk of tremor was found with exposure to both urinary Hg0 exposure (OR, 1.10 [95% CI, 1.00-1.22]) and cumulative Hg0 exposure among younger dentists (< 51 years; OR, 1.13 [95% CI, 1.05-1.22]). ConclusionsOccupational Hg0 exposure in US dentists decreased over time and now is approaching that of the general population. Our results suggest a positive association between Hg0 exposure and tremor. Practical ImplicationsStudies with more sophisticated outcome and exposure measures, and including more retired dentists, would provide critical information toward understanding the relation of Hg0 exposures to MS and tremor risk.