Direct measurement of lead in bone. A promising biomarker.

Chronic excessive exposure to lead is widespread in industrialized societies. In the United States, an estimated 3 million young children have a blood lead level of 0.50 μmol/L (10 μg/dL) or more, the level considered by the Centers for Disease Control and Prevention to indicate increased absorption. 1 Also, more than 1.4 million industrial workers have the potential for chronic exposure through occupations such as stained glass manufacturing, battery making, and bridge demolishing. 2 See also p 197. Despite the extent of this exposure, great gaps exist in our knowledge of the chronic toxicity of lead. 3 For example, we do not know the level of cumulative exposure in adults that is associated with chronic dysfunction of the central or peripheral nervous systems. We do not know whether chronic exposure is associated with motor neuron disease, parkinsonism, or other chronic neurological illnesses. We do not know the fraction of hypertension