The study is organized by the CSP Epidemiology Center program with the Seattle Epidemiologic Research and Information Center serving as the CSP coordinating center. The 2 participating sites are at the VA Boston Healthcare System and Durham VA Medical Center. The pilot study will provide information that will allow the planning of a national, large-scale health study to assess the residual effects of exposure to high levels of particulate matter while deployed. This will help inform VA health policy for Iraq and Afghanistan Veterans.