Evaluation of Internal Doses of Mercury at Intermittent Exposure to Elemental Mercury at the Mine in Idrija

Abstract

Our experience suggested that the urine mercury concentration is not a valid indicator of individual internal doses received during intermittent type of exposure to elemental mercury. We decided to define the current internal dose of mercury through the analysis of total blood mercury. Thirty two miners were observed before and immediately after exposure to elemental mercury. Because the workers made use of respiratory protection, the residual external exposure was assessed with a personal sampler in 15 miners. Blood and urine samples of all examined miners were taken before and immediately after exposure for analysis of total mercury. Total mercury was determined in plasma, erythrocytes and also in the 18-h urine samples of 20 miners. The mercury concentration in all urine postshift samples was corrected to a urinary specific gravity of 1.024 and the postexposure 18-h urine samples of 20 workers was corrected to a urine volume of 1 ml/min. Mercury in the blood, urine and gold trap was determined by cold vapour atomic absorption spectrometry. A very good correlation was found between elemental mercury in inhaled air and the postexposure blood mercury concentration (r = 0.96, P = 0.000). A significant increase (P < 0.001) in blood mercury and urine mercury was established after exposure. The urine and blood mercury concentration after exposure was well correlated (r = 0.68, P < 0.001). No correlation was found between the blood mercury concentration before and after exposure (r = 0.29, P > 0.05). A significant increase (P < 0.01) in erythrocyte mercury and predominantly in plasma mercury was also established during exposure. The correlation between plasma and postshift urine mercury was higher (r = 0.82, P = 0.000) than between erythrocyte and postshift urine mercury (r = 0.70, P = 0.002), if the correction of urine mercury concentration to a urine volume of ml/min was used. Our results confirm that blood mercury concentration is a valid and reliable indicator of current or recent individual exposure to elemental mercury at intermittent type of exposure. At this type and level of exposure, urine mercury in postshift samples, particularly if adjusted to a urine volume of ml/min, reflect not only the accumulation of mercury from earlier exposures but partly also the current group level exposure.