This study will execute 4 distinct efforts to meet the study objectives: (1) enroll a study cohort of up to 6,200 Veterans who live within the catchment area of 6 VA recruitment sites, conduct an in-person assessment of pulmonary function, and collect data on key covariates; (2) create a spatial-temporal exposure grid of environmental PM2.5 levels averaged per week per 1 square kilometer at locations where military personnel served; (3) link each individual's location and duration (spatial-temporal) history during deployed and non-deployed times with averaged PM exposures during each of these time periods; and (4) conduct association analyses to test hypotheses of deployment-related cumulative PM2.5 exposure and current respiratory health by combining exposure data with data collected from the cohort members and from their military records.