The spatial distribution of zinc and cobalt in single human head hairs.
The concentration patterns of indigenous zinc and of zinc and cobalt absorbed from radiotracer solutions have been measured via flameless AA and radioactivity assay, respectively, in individual human head hairs. Patterns for indigenous zinc were found to be relatively flat and featureless. Patterns for absorbed zinc (like those for indigenous and absorbed copper in the same subjects) showed increasing concentrations with increasing distance from the root, plus zones of locally increased concentrations at positions different from those for zones of increased copper concentrations. In bleached hair, indigenous zinc concentrations were decreased, and absorbed zinc and cobalt concentrations were increased compared to values in normal hair. The data for absorbed zinc and cobalt were interpreted in terms of a variable concentration of metal-binding sites in the hair structure, coupled with an increased porosity induced by hair bleaching. The flat patterns for the indigenous zinc content were interpreted as indicating the importance of dietary zinc and incorporation via the follicle, and the unimportance of external contamination as the source of this zinc. The forensic implications of the data have been discussed.