Bioimaging of trace metals in ancient Chilean mummies and contemporary Egyptian teeth by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS)

Abstract

Distributional analysis of trace metals in biological tissue provides important archived toxicological and nutritional information. In this study, lead, strontium, zinc, and lithium concentrations were measured in dental tissue using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Teeth from two populations were sampled: ancient Chilean mummies (n=16) from Arica city as well as recently exfoliated deciduous teeth from contemporary Egyptian children (n=20) living in the Nile Delta. In this study, LA-ICP-MS was used to obtain high-resolution (50μm) elemental bioimages in dental tissue. The experiments consisted of fully quantitative Pb bioimages as well as semi-quantitative Zn and Li bioimages of one contemporary Nile Delta, Egypt tooth and one ancient tooth from the Andes. Lead levels in the Egyptian teeth averaged an order of magnitude greater than in the ancient Chilean teeth (14.93±32.28μg/g and 1.33±0.84μg/g, respectively), and had a much greater range of variation among teeth (1.02μg/g–68.38μg/g versus 0.36μg/g–2.35μg/g, respectively). Lithium, an element widely present in northern Chile, was found in higher concentrations in the Arica teeth than in the Kalama teeth, with the highest concentrations at two sites in Chilean burial grounds where water is tainted with natural lithium. Micrometer resolution images of quantified Pb, Zn, and Li concentrations from two teeth revealed higher concentrations of Pb and Zn in the pulp and surface enamel. Zn and Li are concentrated in the crown, potentially indicative of higher prenatal exposure.