Exposure to Mercury Vapors in Dental Workers in Poland

Abstract

The study aimed at assessing the effect of low-level exposure to mercury (Hg) vapor from amalgam fillings among dental surgery staff in the city of Łódź, Poland. The study group was composed of 51 workers (mean age, 39.25+/-11.05 years) employed in dental surgeries; the control group comprised 16 white-collar workers (mean age, 40.05+/-10.57 years) of the Nofer Institute of Occupational Medicine, Łódź, who had no or a few amalgam dental fillings. Total urine mercury (Hg-U) concentration was determined with cold vapor atomic absorption spectrometry (CV-AAS) based on tin (II) chloride mercury reduction after overnight digestion of urine sample with potassium permanganate in sulfuric acid solution. The reliability of mercury determinations was verified by measuring Hg concentration in the reference material and via participation in the external quality assessment scheme. No statistically significant differences were found in geometric mean of urine Hg concentrations between the study and control groups (GM+/-SD, 0.44+/-0.440 and 0.5+/-0.270 mug/g creatinine, respectively, p = 0.242). Among different factors affecting Hg exposure in dental surgeries, only the duration of dental practice showed a statistically significant influence on total Hg-U (r = 0.3000; p = 0.024). Having divided the subjects into two groups, with and without amalgam fillings, we noted a statistically significant difference in urine Hg concentrations (0.60 +/- 0.720, n = 38; 0.36 +/- 0.650, n = 29; p = 0.004) between these two groups. The results of biological monitoring of dental surgery staff did not reveal current exposure to Hg vapors from amalgam fillings. However, these dental workers may have been the subject to such an exposure in the past. The only statistically significant correlation was that between total Hg-U concentrations and the duration of dental practice.