Abstract

The measurement of urinary mercury excretion is presently the main tool used in making decisions about the preventive reassignment of pregnant or breast-feeding workers exposed to inorganic mercury. To help physicians make informed decisions in this area, it was useful to quantify the variability of urinary mercury excretion in the same individual and to document the factors that may affect urinary levels. This study reveals that between one and three screenings – preferably performed at the same time of day – may be required to reach an informed decision on preventive reassignment. In addition, at least six months of exposure may be necessary for the measurement of urinary mercury to reliably reflect exposure levels. For any result exceeding 2.0 nmol/mmol of creatinine – the threshold value presently used by physicians of the public health network as a criterion for reassignment – it is important to document the possibility of non-occupational exposure. For populations not exposed occupationally, dental amalgams, food, air and drinking water are the main factors affecting inorganic urinary mercury excretion.