Lead contents in the surface enamel of deciduous teeth sampled in vivo from children in uncontaminated and in lead-contaminated areas

Abstract

This study aimed to: (1) measure lead contents in the surface enamel of two populations consisting of 4-6-year-old children, one from an apparently uncontaminated area (Ribeirão Preto, São Paulo State, SP, Brazil, n=247) and the other from an area notoriously contaminated with lead (Bauru, São Paulo State, Brazil, n=26); (2) compare biopsy depths between the two populations; (3) correlate biopsy depth with lead content; (4) stratify samples according to biopsy depth to compare lead contents in samples from similar biopsy depths. A surface enamel acid-etch microbiopsy was performed in vivo on a single upper deciduous incisor for each sample. Lead was measured by graphite furnace atomic absorption spectrometry (GFAAS) while phosphorus was measured colorimetrically to establish biopsy depth. Samples from both populations were classified into categories of similar biopsy depths based on biopsy depth quartiles. Median lead contents were statistically different between the Ribeirão Preto population (206 microg/g, range: 5-1399 microg/g) and the Bauru population (786 microg/g, range: 320-4711 microg/g) (p<0.001); however, biopsy depth did not differ between the Ribeirão Preto (3.9 microm, Standard Deviation, SD=0.9) and Bauru (3.8 microm, SD=0.9) populations (p=0.7940). Pearson's correlation coefficient for biopsy depths versus log10 lead values was -0.29 for Ribeirão Preto and -0.18 for Bauru. Lead contents were statistically different between the two populations for all quartiles of biopsy depth. These findings suggest that lead accumulated in the surface enamel of deciduous teeth is linked to the environment in which people reside, indicating that this tissue should be further explored as an accessible biomarker of lead exposure.