Hair as Biomarker of Toxic and Essential Trace Elements in Children

Abstract

Background/Aim: Metals and other trace elements in hair have been commonly used as exposure biomarkers, as hair collection is non-invasive. However, concern has been raised regarding the appropriateness for assessing the actual absorbed dose. The aim was therefore to evaluate children’s hair as biomarker of internal dose for toxic (As, Mn, Cd, Pb) and essential (Mg, Ca, Fe, Co, Cu, Zn, Se, Mo) elements. Methods: In 207 children (9-10 years), belonging to a mother-child cohort in rural Bangladesh, we measured concentrations of the selected elements in hair (2 cm closest to the scalp) by ICP-MS, following Triton X-100 washing and acid digestion. We compared these concentrations with those in blood (erythrocyte fraction), urine and water, collected about six months earlier. For a sub-set of children (n=19), we analyzed four consecutive 2 cm-pieces of hair. Results: There were significant correlations between hair As and the other biomarkers (blood: rs=0.73, p<0.001; urine: rs=0.66, p<0.001) and water (rs=0.60, p<0.001), and between Se in hair and blood, especially when assessing Se in hair and blood representing the same time period, i.e. the 7-8th cm of hair (rs=0.54, p=0.026), assuming one cm growth per month. Suitability of hair-Se as exposure biomarker was supported by associations with cognitive abilities. Hair Co and Mo showed weak correlations with concentrations in blood. We found no associations between Mn in hair and blood, urine, or water, and the geometric mean concentration increased almost 5 times from the 2 cm closest to the head to the 7-8th cm (p<0.001). Also Mg, Ca, Co, Cd, and Pb increased from the scalp outwards (p<0.001). Conclusions: Hair was found to be appropriate for assessment of absorbed As and Se only. Out of all measured elements, hair Mn seemed the least reflective of internal dose.