ANALYSIS OF RETAINED DUST CHARACTERISTICS IN LUNG TISSUE FROM PREVIOUSLY DEPLOYED MILITARY PERSONNEL

Military personnel deployed to Southwest Asia and Afghanistan may develop persistent respiratory symptoms and diseases such as asthma and bronchiolitis. Cell line and animal studies using desert topsoil and airborne dust from Iraq and Afghanistan have shown lung inflammation and injury. Few studies have analyzed characteristics of retained dust in military personnel with histopathologically-confirmed lung injury. We examined particle load, size, modal mineralogy, and chemistry of dust recovered from lung tissue blocks collected via surgical lung biopsy from 24 previously deployed military personnel (“deployers”) with small airway and distal lung abnormalities compared to 11 normal control donated lung specimens. We used mixed models in SAS v.9.4 with random effects to account for multiple measurements and/or samples for some subjects and data transformations and/or offsets, as appropriate. In situ lung particulate matter (PM) was classified as silica, aluminosilicates, other silicates, metals, carbonaceous, or other. We found that all PM categories were evenly distributed between upper and lower lobes. Mean particle length (p=0.43) and area (p=0.65) were generally shorter among deployers compared to controls, though differences were not statistically significant for any of the PM categories. The relative particle load of silica, aluminosilicates, and other silicates was higher among deployers compared to controls, but was not statistically significant. The load of carbonaceous, metals, and other phases was higher in controls than deployers but was only significantly higher for the ‘other phase’ category (p=0.04). The lung silica burden was higher in deployers reporting either no/low sandstorm exposure (p=0.15) or medium/high exposure (p=0.21) compared to controls, while the aluminosilicates burden was not significantly different between deployer exposure groups compared to controls (p=0.35 and p=0.89, respectively). In summary, analysis of retained lung dust may provide insight into persistent lung inflammation, though access to adequate numbers of tissue samples remains challenging. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.