Inductively coupled plasma-mass (ICP-MS) and atomic emission spectrometry (ICP-AES): Versatile analytical techniques to identify the archived elemental information in human teeth

Human dental enamel is composed of sequentially calcifying growth layers that can provide an archival record of temporal changes such as past pollution events and changes in elemental nutrition. Human teeth and bones alike are mainly made out of calcium and a phosphorous rich crystalline building block called hydroxyapatite [Ca10(PO4)6(OH)2]. Divalent cations such as Zn2+, Pb2+, Sr2+, and Mg2+ can replace isovalent calcium sites, and phosphate and hydroxyl sites can substitute with anions, such as carbonate and fluoride, respectively. In this investigation inductively coupled plasma-atomic emission (ICP-AES) and mass spectrometry (ICP-MS) was used to determine lead, zinc, and strontium concentrations in deciduous teeth from contemporary populations from Solís, Mexico and Kalama, Egypt and permanent teeth from Bronze age Tell Abraq, United Arab Emirates and the 18th century New York African Burial Ground (NYABG) from Lower Manhattan. The concentration of lead in children's teeth from a semi-urban village in Egypt (ranged from 162 to 2.6 μg g−  1; n = 10) and NYABG individuals (range 112-1.2 μg g− 1; n = 6) showed the elevated lead levels while the ancient population from Tell Abraq had the lowest level (1.34 to 0.03 μg g− 1; n = 10). Lead isotope ratios (i.e., 208Pb/206Pb and 207Pb/206Pb) of above individuals' teeth were measured using ICP-MS to discern their domicile. Zinc and Sr concentrations of teeth reflect the diet, nutritional and environmental history of individuals. The versatility of ICP-AES and ICP-MS as trace metal analytical techniques in unraveling elemental information embedded in hard tissue, like teeth, is demonstrated.