METAL DISTRIBUTIONS AND ASSOCIATIONS IN LUNG TISSUE: A MICRO-X-RAY FLUORESCENCE STUDY OF SOLDIERS’ LUNGS

Some U.S. soldiers returning from the Middle East theaters are showing an unusual incidence of pulmonary pathophysiology of unknown origin. Particularly, an increased incidence of asthma has been observed in patients that exhibited no asthmatic symptoms prior to deployment. Analysis of anonymously-coded lung tissue biopsy sections from three Iraq/Afghanistan veterans with post-deployment pulmonary illnesses to evaluate metal associations, distributions, and speciations within the tissue holds clues to metal contaminant sources and possible disease origins.

For this study, three affected tissues and one control tissue were analyzed using synchrotron microbeam X-ray fluorescence (µ-XRF), X-ray diffraction (µ-XRD) and X-ray absorption near edge spectroscopy (µ-XANES) at the National Synchrotron Light Source, beamline X26A.

Light microscopy of the three affected tissues reveals dark grain aggregates throughout. Compositional mapping using µ-XRF shows that these grain aggregates correlate with the distribution of elevated levels of iron and titanium, what we refer to as metal “hotspots.” Quantitative µ-XRF analysis of these metal hotspots shows that iron/titanium ratios are variable among hotspots within a single tissue and across all tissue samples (means range from 7:1 to 40:1), suggesting that iron and titanium may not originate from a single source or that there is variable dissolution of particles within the lung. Results from µ-XRD show that aggregates are composed of a mixture of mineral phases including the mineral rutile. Titanium µ-XANES results indicate that titanium is predominantly found in the +4 oxidation state and that the local coordination is most similar to rutile. Results demonstrate how application of microfocued synchrotron X-ray techniques to diseases that affect human lung tissue can provide high-resolution analysis of inhaled particulates with high sensitivity at low concentrations. These techniques can be used to explore the geochemistry of lung contaminants, which has the potential to affect patient care and long-term health outcomes of veterans.