Major Limitations in Using Element Concentrations in Hair as Biomarkers of Exposure to Toxic and Essential Trace Elements in Children

BACKGROUND: Hair is a commonly used exposure biomarker for metals and other trace elements, but concern has been raised regarding its appropriateness for assessing the internal dose. OBJECTIVES: The aim of the present study was to evaluate children's hair as biomarker of internal dose for toxic (As, Mn, Cd, Pb) and essential elements (Mg, Ca, Fe, Co, Cu, Zn, Se, Mo). METHODS: In 207 children (9-10 years of age), originating from a population-based cohort in rural Bangladesh, we measured concentrations of the selected elements in hair (closest to the scalp) using ICP-MS. We compared these with previously measured concentrations in erythrocytes, urine, and water. For a subset of children (n=19), we analyzed four consecutive 2 cm pieces of hair. RESULTS: There were strong associations between hair As and the other biomarkers (erythrocytes: rs=0.73, p<0.001; urine: rS=0.66, p<0.001); and water (rs=0.60, p<0.001); and there were significant correlations between Se in hair and erythrocytes (overall rs=0.38, p<0.001), and urine (rs=0.29, p<0.001). Hair Co and Mo showed weak correlations with concentrations in erythrocytes. Hair Mn was not associated with Mn in erythrocytes, urine, or water, and the geometric mean concentration increased almost five times from the 2 cm closest to the head to the 7th-8th cm (p<0.001). Also Mg, Ca, Co, Cd, and Pb increased from the scalp outward (>50% higher in 7th-8th cm compared with 1st-2nd cm, p<0.001). CONCLUSIONS: Hair was found to be a useful exposure biomarker of absorbed As and Se only. Of all measured elements, hair Mn seemed the least reflective of internal dose. https://doi.org/10.1289/EHP1239.