Trace element analysis of human tooth enamel by laser ablation-inductively coupled plasma-mass spectrometry for estimation of region of origin

Abstract

Tooth enamel is among the most durable substances in the human body and as such has high recoverability in forensic anthropology cases. Its crystalline hydroxyapatite matrix has a slightly variable chemical composition which incorporates biologically available trace elements. The trace elements are derived from an individual's diet and the water he or she consumes during the period of enamel formation. As a result, trace element profiles of enamel can reflect the geology, pollution, and certain cultural dietary factors of the area in which the individual resided during this period.

This research examines a sample of teeth with known demographic information from the Antioquia Modern Skeletal Reference Collection in Medellin, Colombia. A sample set of 75 teeth from 61 individuals born in areas throughout northwestern Colombia were analyzed using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), a minimally destructive, semi-quantitative technique. Analysis was performed at the Center for Archaeology, Materials, and Applied Spectroscopy (CAMAS) at Idaho State University.

33 elements were analyzed in the sample. Nonparametric methods were used to assess the relationship between elemental profiles and region of origin. Sr, Mo, Ag, Ba, Eu, and Tm concentration profiles were found to vary among regional groups. Al, Ni, Cr, Mn, Co, Sr, Cd, Sb, Sm, Eu, and U were found to predict region of origin. Differences in municipality were classified with 72% accuracy, variation across the department of Antioquia was classified with 67% accuracy, and the age of the geologic substrate was classified with 67% accuracy. The results suggest that trace element analysis of permanent tooth enamel may be of some use in estimating an individual's region of origin in forensic anthropological contexts. Further research with both larger sample sizes and more geographic variation is necessary.