| A Critical Review of Biomarkers Used for Monitoring Human Exposure to Lead: Advantages, Limitations, and Future Needs Fernando Barbosa Jr.,1 José Eduardo Tanus-Santos,1 Raquel Fernanda Gerlach,2 and Patrick J. Parsons3 1Department of Pharmacology, Faculty of Medicine of Ribeirão Preto, University of São Paulo,Ribeirão Preto, Brazil; 2Department of Morphology, Estomatology and Physiology, Dental School of Ribeirão Preto, University of São Paulo,Ribeirão Preto, Brazil; 3Wadsworth Center, New York State Department of Health, Albany, New York, USA Abstract
Lead concentration in whole blood (BPb) is the primary biomarker used to monitor exposure to this metallic element. The U.S. Centers for Disease Control and Prevention and the World Health Organization define a BPb of 10 µg/dL (0.48 µmol/L) as the threshold of concern in young children. However, recent studies have reported the possibility of adverse health effects, including intellectual impairment in young children, at BPb levels < 10 µg/dL, suggesting that there is no safe level of exposure. It appears impossible to differentiate between low-level chronic Pb exposure and a high-level short Pb exposure based on a single BPb measurement ; therefore, serial BPb measurements offer a better estimation of possible health outcomes. The difficulty in assessing the exact nature of Pb exposure is dependent not so much on problems with current analytical methodologies, but rather on the complex toxicokinetics of Pb within various body compartments (i.e., cycling of Pb between bone, blood, and soft tissues) . If we are to differentiate more effectively between Pb stored in the body for years and Pb from recent exposure, information on other biomarkers of exposure may be needed. None of the current biomarkers of internal Pb dose have yet been accepted by the scientific community as a reliable substitute for a BPb measurement. This review focuses on the limitations of biomarkers of Pb exposure and the need to improve the accuracy of their measurement. We present here only the traditional analytical protocols in current use, and we attempt to assess the influence of confounding variables on BPb levels. Finally, we discuss the interpretation of BPb data with respect to both external and endogenous Pb exposure, past or recent exposure, as well as the significance of Pb determinations in human specimens including hair, nails, saliva, bone, blood (plasma, whole blood) , urine, feces, and exfoliated teeth. Key words: biomarkers, biomonitoring, blood, bone, feces, hair, lead, plasma, saliva, teeth, toxicokinetics, urine. Environ Health Perspect 113: 1669-1674 (2005) . doi:10.1289/ehp.7917 available via http://dx.doi.org/ [Online 11 August 2005]
Address correspondence to F. Barbosa Jr., Department of Pharmacology, Faculty of Medicine of Ribeirão Preto, University of São Paulo-FMRP-USP, Av. Bandeirantes, 3900, Monte Alegre, CEP 14049-900, Ribeirão Preto, SP, Brazil. Telephone: 5516 6023183. E-mail: fbarbosajr@yahoo.com The authors declare they have no competing financial interests. Received 11 January 2005 ; accepted 10 August 2005.
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