Are dust we breathe toxic?
- Eshani Hettiarachchi, Ph.D.
- Mar 9
- 2 min read
Originally published on April 1, 2022
Cardiovascular and metabolic disease rates remain high among Native American residents near the many abandoned uranium mines in the Grants Mining District in western New Mexico, USA. One explanation is the exposure to uranium-containing inhalable dust. However, little we know about how depleted uranium interacts with the body inside the lungs. Depleted uranium is uranium with very low radioactivity than usual.
Does dust survive in the lungs or is harmlessly excreted by the body? Does it dissolve into the bloodstream, if so, is it harmful?
To find out, we conducted a study by collecting dust from five different sites near the Jackpile mine and the St. Anthony mine within 1.5 miles of a local community in Grants, NM, USA. First, we characterized dust samples for their mineral contents. Then we dissolved these samples in two different fluids meant to simulate two conditions inside human lungs. These fluids are namely Gamble’s solution and artificial lysosomal fluid. Gamble’s solution (GS) mimics the interstitial conditions. Artificial lysosomal fluid (ALF) mimics the intracellular conditions in the alveolar macrophages during phagocytosis, the process of engulfing particles by the cell plasma.
Then we analyzed the results, looking at the changes in dissolved uranium content during dust interaction with the simulated lung fluids. Among others, we discovered that uranium could dissolve in the lungs forming a toxic chemical form known as uranyl cation (UO2 2+). Uranyl cation could irreversibly bind to DNA, leading to adverse health effects.
We also found that the specific mineralogy of the dust impacts how these fluids interacted with the uranium. The uranium dissolutions, modeled by introducing one mineral at a time, suggested that autunite, carnotite, tyuyamunite, and uraninite were more soluble in GS than in ALF, with total dissolved uranium concentration (TDU) in GS/ALF ratios of 1.58, 16.11, 17.79, and 1.01, respectively. The minerals schoepite, torbernite, coffinite, and uranophane were more soluble in ALF than in GS, with TDU in GS/ALF ratios of 0.58, 0.26, 0.95, and 0.26, respectively.
Overall, we found that dust inhalation followed by dissolution may cause adverse toxic effects due to the compositional changes (i.e., pH, speciation, and ionic strength) in the lungs. Therefore, we suggest that understanding the behavior of inhaled Uranium containing-dust in these mining areas with a specific focus on site mineralogy is vitally important.