Spatial Distribution of Lead in Teeth: Towards New Biomonitoring Methodologies

Lead is the second most hazardous environmental toxin known. Health effects of lead exposure include neurological impairment, renal dysfunction, hypertension, anaemia, dental caries and enamel hypoplasia. At present, no suitable biological marker exists for lead exposure during the crucial prenatal and neonatal periods of development. Objectives: To develop a new bio-monitoring methodology that utilizes the spatial distribution of lead along the incremental zones in naturally exfoliated primary teeth to estimate the intensity and pattern of exposure to lead during the prenatal and neonatal periods. Methods: An animal model was developed in which forty Wistar rat pups were exposed to controlled doses of lead through maternal drinking water during the prenatal and neonatal periods. The spatial distribution of lead in the incremental zones of enamel and coronal dentine was measured using a Nuclear Microprobe. Lead concentrations in kidneys, liver, brain and blood were determined by Inductively Coupled Plasma Mass Spectrometry. Results: The spatial distribution of lead along incremental zones in the coronal dentine correlated strongly with the pattern and intensity of exposure (r=0.70). Lead concentrations in teeth showed strong positive correlations with lead levels in kidneys (r=0.80), livers (r=0.90) and brains (r=0.88). Most importantly, tooth-lead was a better predictor of body burden than blood-lead (p<0.05). Conclusions: The spatial distribution of lead along incremental zones in coronal dentine is a strong predictor of the intensity and pattern of exposure, and body burden of lead during the prenatal and neonatal periods. This methodology is being applied in an epidemiological study in the Broken Hill region of NSW, Australia, where environmental lead exposure continues to be a major health issue. Financial support has been provided by ADRF, NSW Dental Board, the Australian Synchrotron Programme, ANSTO and the Faculty of Dentistry, University of Sydney.