| Tooth Analyses of Sources and Intensity of Lead Exposure in Children Brian L. Gulson Graduate School of the Environment, Macquarie University, Sydney, NSW 2109 and CSIRO/EM, North Ryde, NSW 2113 Australia Abstract
The sources and intensity of lead exposure in utero and in early childhood were determined using stable lead isotopic ratios and lead concentrations of incisal and cervical sections of deciduous teeth from 30 exposed and nonexposed children from the Broken Hill lead mining community in Australia. Incisal sections, consisting mostly of enamel, generally have low amounts of lead and isotopic compositions consistent with those expected in the mother during pregnancy. Cervical sections, consisting mostly of dentine with secondary dentine removed by resorption and reaming, generally have higher amounts of lead than the enamel and isotopic compositions consistent with the source of postnatal exposure. There are statistically significant differences in lead concentrations between incisal and cervical sections, representing within-tooth variation, for children with low and high lead exposure (p = 0.0007, 2 X 10-6, respectively) and for those who have ingested leaded paint (p = 0.009) . Statistically significant differences between incisal and cervical sections in these three exposure groups are also exhibited by the three sets of lead isotope ratios (e.g., p = 0.001 for 206Pb/204Pb ratio in the low exposure group) . There are statistically significant differences between the low and high lead exposure groups for lead concentrations and isotopic ratios in incisal (p = 0.005 for lead concentration and 6 X 10-6 for 206Pb/204Pb ratio) and cervical sections (p = 5 X 10-5 for lead concentration and 6 X 10-6 for 206Pb/204Pb ratio) . The dentine results reflect an increased exposure to lead from the lead-zinc-silver mineral deposit (orebody lead) during early childhood, probably associated with hand-to-mouth activity. Leaded paint was identified as the source of elevated tooth lead in at least two cases. Increased exposure to lead from orebody and paint sources in utero was implicated in two cases, but there was no indication of previous exposure from the mothers' current blood leads, suggesting an acute rather than a chronic exposure for the mothers. Permanent teeth from one subject had lower amounts of lead in the roots compared with the crowns, and the isotopic composition of the crowns were consistent with the data for the deciduous teeth from the same subject. Based on changes in the isotopic composition of enamel and dentine, it is provisionally estimated that lead is added to dentine at a rate of approximately 2-3% per year. Key words: children, teeth, lead exposure, pregnancy. Environ Health Perspect 104:306-312 (1996)
Addresss correspondence to B. L. Gulson, Graduate School of the Environment, Macquarie University, Sydney, NSW 2109 Australia. I thank the "tooth fairies" from Broken Hill who kindly procured the teeth ; Garry Lenard for identification of the teeth ; Michael Korsch for keeping the mass spectrometers in top condition, for software development, and for ongoing fruitful discussions ; Andrew Smith of CSIRO Division of Mathematics and Statistics for statistical advice and for Figures 3 and 4. Michael Korsch, Michael Moore, and Michael Rabinowitz reviewed an early version of this manuscript ; a thorough, constructive review by an EHP peer reviewer assisted greatly in revising this paper ; and Brian J. Thomas made comments on the final version. Received 22 March 1995 ; accepted 28 November 1995.
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