PULMONARY PATHOGENICITY OF AMBIENT PARTICULATE DUST FROM IRAQI MILITARY FIELDS

It has been recognized since early in Operation Iraqi Freedom/Operation Enduring Freedom that service members deployed to Southwest Asia are exposed to extremely high levels of ambient particulate matter; chiefly of geologic origin. However, there is a lack of rigorous studies supporting an evidence-based assessment of the risk of respiratory disease associated with particulate matter during deployment. We collected two samples of ambient particulate matter at Camp Victory, one in the spring of 2008 (I8) and one in the spring of 2009 (I9) and exposed rats to these materials by intratracheal instillation. The response of the rats to the particulate matter was followed for up to 150 days after the single instillation. Freshly fractured silica and a standard sample of urban particulate matter (UPM) were used as references. A range of biochemical and immunological variables in lung lavage fluid was examined as well as lung histomorphology. All materials caused an initial inflammatory response which declined over time except in the case of silica. As expected, the freshly fractured silica caused the most profound effects at later time points; while the UPM, I8, and I9 exposures produced only marginal effects. The initial inflammatory responses suggest that the I8 and I9 dusts could cause asthma-like symptoms in humans. At longer time periods, the UPM, I8, and I9 exposures were associated with emphysematous changes and bronchiolarization of the small airways. Repeated and long term exposures may result in more severe effects. Research was conducted in compliance with the Animal Welfare Act, and all other Federal requirements. The views expressed are those of the author and do not constitute endorsement by the U.S. Army.