The Variation of Trace Element Concentrations in Single Human Head Hairs

Abstract

Hair from the human body is frequently encountered in the examination of crime-scene physical evidence. Study of metallic components by neutron activation analysis (NAA) and application of the results of such studies in forensic work, have been made difficult by the complexity of the hair system and its attendant surface contamination. As was noted in 1967 [1], “virtually everyone working with hair by this method [NAA] uses a different type of sampling, and a different method of cleaning the hair, and nobody yet really knows enough about the basic chemistry, morphology and behaviour of the hair shaft to be able to assess reliably the significance of the results.” The literature [2,3] contains both optimistic and pessimistic prognoses of the possibility of establishing whether or not a hair came from the head of a given individual.

Provenance of Ancient Textiles—a Pilot Study Evaluating the Strontium Isotope System in Wool*

“…There is a steady increase of Sr concentrations in this sample from the distal end (~6 ppm) to the proximal (root) end (~15 ppm) portions of the hair, accompanied by a slight (but statistically discernable) increase of the 87 Sr/ 86 Sr ratios of the respective residues (from 0.7093 to 0.7098; Table 1). The decreasing concentration trend from distal to proximal disagrees with observations by Obrusnik et al (1973), who reported increasing concentrations of some trace elements towards the distal end in human scalp hair. Generally, such variations reflect the slightly changing bioavailable Sr (in the case of our wool/hair study) over the period of the wool growth (~1 year), possibly by moving around between different pastures.…”

Elemental ratios along human hair as indicators of exposure to environmental pollutants

“…Because of its growth, hair reflects previous elemental concentrations in serum and body (history of previous biochemical and medical events in man), as well as previous environmental effects. Several measurements of trace element distributions have been reported (13)(14)(15)(16). The investigators agree that the variations are characteristic of the subject and that Zn variations along hair are negligible.…”

Hair Research

“…Since several authors have indicated (Obrusnik et a!., 1972;Eads and Lambdin, 1973) that zinc variations along single hairs are small, in order to obtain the distribution of elemental concentrations along the hair, one may measure just the elemental concentration relative to zinc. Such relative measurements can be easily performed on single hairs with proton-induced X-ray emission spectroscopy (Valkovic et aI., 1974).…”