MINERALOGY DEPENDENT DISSOLUTION OF INHALED URANIUM IN SIMULATED LUNG FLUIDS IN URANIUM MINE LANDS, NEW MEXICO

The finest dust particles (PM₁₀ or less) can pass through the physical filters in our respiratory tract, ultimately reaching the lungs through inhalation. In places where mining occurred, these dusts were long considered a health problem due to contamination with heavy metals such as uranium. Upon inhalation exposure, metals could either accumulate inside the lungs and cause radiation damage or dissolve in lung fluids and enter the blood stream, where they may excrete or stay complexed with other biological components. While excretion can be treated as less toxic, uranium complexation in human biological systems may yield different health conditions depending on several factors, including the mineralogy of uranium in the source material.

In this study, leaching of uranium from (1) dust samples collected around Jackpile Mine area, (2) fine-grain sediments from St. Anthony Mine, and (3) a U₃O₈ standard was investigated in two different simulated lung fluids (SLF). The two SLFs mimic two different lung conditions: Gambel’s solution (GS) simulates the upper lung conditions with which inhaled dust first interacts, while Artificial Lysosomal Fluid (ALF) mimics the lung conditions at phagocytosis, a defensive mechanism against foreign inhaled bodies. Our results indicate that the dissolution of uranium in dust in these two different SLFs depends not only on the fluid pH and composition but also on the uranium mineralogy of the source material and on the mode of sediment transport. Dust transported via wind demonstrates higher dissolution in GS while dusts and sediment collected around mine pits are more soluble in ALF. The ability of uranium to complex with the organic and inorganic ligands in these lung fluids may alter the composition, thereby disturbing body functions. Therefore, uranium mineralogy may play an important role in leaching inside the lungs and in subsequent complexation, potentially influencing any resultant health impact.