Mass Balance and Systemic Uptake of Mercury Released from Dental Amalgam Fillings

Abstract

The release of mercury (Hg) from dental amalgam fillings has been verified by several authors. In this study, the emission rate of Hg°-vapor from the oral cavity (O-Hg) and the urinary Hg-excretion rate (U-Hg) have been studied with 34 healthy individuals. In ten cases, the urinary excretions of silver (U-Ag) and the fecal excretions of Hg and Ag (F-Hg, F-Ag) were also monitored. All variables, except U-Ag, were significantly related to the load of amalgam. According to this study, an individual with a moderate load of ar lalgam, i.e. 30 restored surfaces, is predicted to exhibit the following emission rates: O-Hg=22, U-Hg=3, F-Hg=60 and F-Ag=27 µg/d (d=24 hours), consistent with a gross mass balance for Hg of approximately 60 µg/d. The corresponding systemic uptake of Hg was estimated to 12 µg/d based on external data relating air Hg°-exposures to urinary Hg-excretions. The worst case individual showed a gross mass balance of 200 µg Hg/d connected to a systemic uptake of 70 µg Hg/d. These values were compared to the average intake of to al-Hg by a Swedish diet (2 µg/d) and to the WHO’s tolerable value for intake of total-Hg by food (45 µg/d). Upscaled to the entire Swedish population (8 mill.), the data suggests a fecal/urinary emission to the environment of 100 kg Hg yearly originating from a population load of amalgam fillings containing 90,000 kg of Hg.