Urine mercury levels and associated symptoms in dental personnel

Dental personnel are exposed to low concentrations of mercury vapor in their working environment and from their own amalgam fillings. This study included 505 occupationally exposed individuals working at 82 dental clinics in northern Sweden and 41 controls without occupational mercury exposure. The concentration of mercury in air was measured. Urine mercury was determined for all participants, who also answered a questionnaire focused on four symptoms known from the literature to be connected with mercury exposure, namely loss of appetite, tremor, insomnia and anxiety. The median value of mercury vapor in air in the dental surgeries was low compared with other investigations; 1.5 micrograms m-3 in public dental care and 3.6 micrograms m-3 in private dental care. The urine mercury concentrations (HgU) were low, and of the same order of magnitude as for the Swedish population as a whole. Median values among different groups of dental personnel ranged from 1.4 to 2.9 nmol Hg/mmol creatinine. For those occupationally exposed, the load from their own amalgam fillings was estimated to be of the same order of magnitude as from the working environment. The prevalence of any of the four symptoms investigated in the groups of exposed personnel and controls as low, less than or equal to 11%. In our study, which included mercury intakes up to twice the contribution from amalgam fillings, no increase in the prevalence of symptoms could be detected in relation to mercury concentrations in urine.