A plateau detected in lead accumulation in subsurface deciduous enamel from individuals exposed to lead may be useful to identify children and regions exposed to higher levels of lead

In a previous study, we showed 4 times more lead in surface deciduous enamel (1.9–5.9 μm) of a notoriously contaminated area (Bauru, São Paulo State, Brazil) in comparison to samples from a region with no lead contamination described (Ribeirão Preto, São Paulo State, Brazil). The samples from the more superficial enamel (1.9–3.18 μm) showed higher amounts of lead and the highest variability, while in the subsurface enamel (3.18–5.9 μm) a plateau in lead content was detected in children living in the contaminated environment (around 600 μg/g). Here we expand our previous study, and use only samples obtained from subsurface enamel (Ribeirão Preto, n=186; Bauru, n=20). We tried to distinguish regions with more children with lead above the threshold of 600 μg/g of lead in enamel. We tested whether differences in the percentage of children with ‘‘high” lead (⩾600 μg/g) could be observed among the different Kindergartens studied in Ribeirão Preto. We also tested whether these results were different from the ones provided by conventional comparison of the data. Ribeirão Preto showed almost 4 times less lead than Bauru (p<0.0001), and a statistically significant difference was found only in Ribeirão Preto between Kindergarten 2 and 5 (p<0.01). Twelve percent of the children from Ribeirão Preto had “high” lead, while 55% of the children from Bauru did so. However, when we looked at the percentages of children with “high” lead in each Kindergarten, and compared them, a whole new picture emerged, in which we could see children with “high” lead concentrated mainly in 3 Kindergartens from Ribeirão Preto, with Kindergarten 5 with 33% of the children with “high” lead, being statistically different from all Kindergartens, except 4 and 6. The threshold of 600 μg/g of lead in subsurface enamel was tentatively settled here after the plateau seen in exposed children, and enabled us to identify locations with more children exposed to a higher amount of lead.