[Reference values for trace elements in biological fluids].

The assessment of reliable reference ranges for the concentrations of elements in biological fluids is necessary to evaluate the risks deriving from occupational and environmental exposure. For the production of reference ranges in this field it is necessary to adhere to strict criteria for the selection of individuals, the procedures for sample collection, the control of analytical variability and the statistical treatment of results. The factors affecting analytical and biological variability of the concentrations to be determined, such as the route of absorption, the presence of sources of environmental pollution in certain areas of residence, physiological variables and life-styles, are discussed.