Abstract:
Hair is a unique matrix for metal deposition, as it offers a “timeline” of prior exposures (Stadlbauer et al., 2005). This spatiotemporal relationship of exposures along the hair can make possible the estimation of time and duration of exposures. Metals are known to deposit in the hair, and thus are a group of toxicants whose interventions and treatment could be aided by this timeline of information. Our study aimed to validate Laser Ablation Inductively Coupled Mass Spectroscopy (LA-ICP-MS) for measuring zinc in human hair samples and to use zinc supplementation to determine individual hair growth rates. Twenty-one participants took zinc gluconate supplements two weeks apart, followed by a hair sample collection two weeks later. This study design aimed to produce two measurable exposures to zinc in the hairs of participants, from which hair growth rates could be calculated. These samples were washed, mounted, and analyzed after several experiments to optimize our analysis method. Although we ultimately were unable to measure hair growth rates using these hair samples, we were able to characterize concentrations of zinc, lead, and mercury in hairs from participants, and determine between and within subject variability in concentrations of those elements. In addition, we identified a suitable washout period to minimize carryover of analyte between successive samples, and we identified helium collision cell gas flows that minimized polyatomic interferences without compromising sensitivity for LA-ICP-MS. This analysis technique benefits the field of environmental health by offering time-resolved exposure information on public health-relevant metals such as zinc, lead, and mercury. This dissertation contributes meaningful method development on this application for LA-ICP-MS.