Trace Element Composition of Modern Human Bone

Abstract

The utilization of trace elements in medical, biological, anthropological, and/or geographic provenance studies of human biominerals requires an understanding of trace element incorporation into human bones. While the majority of research has focused on the incorporation of a select group of elements (F, Sr, Pb, K, Mg, Zn, and Na), little information exists on the abundance and incorporation of most geologically significant trace and rare earth elements, specifically those that may have a utility for geographic provenance studies. Because trace element patterns vary according to geological processes, the chemical composition of different geographic areas are often distinguishable. As a result, trace elements may be useful for dietary or forensic geographic provenance studies. However, trace element incorporation into bone depends also upon dietary and metabolic processes in addition to the chemical composition of an individual's geographic domicile. We use ICP-MS analyses for 38 trace elements in cortical bone tissues of 58 patients who underwent hip replacement surgery to investigate trace and rare earth element incorporation into modern human bones. We develop a standard system for the evaluation of trace elements including incorporation coefficients (Ki) and ratios of incorporation (Ri) that allow comparison of the levels of incorporation for various trace elements and develop systematics to determine which elements are controlled by metabolic activity as opposed to dietary or environmental factors. Elements that are not strongly affected by metabolic activity (e.g., oxyanions, REEs, Ba, U, and Th) may be directly linked to geographic location or dietary inputs. We find that trace element incorporation occurs systematically according to predictable physiochemical parameters including ionic radius, valence state, and solubility. Ratios of incorporation (Ri) values for trace element concentrations in bone quantify the relative deviation for each trace element from the theoretical geological standard for average soil composition of the continents (UCC).