Exposure to particulate matter (PM) air pollution is an established risk factor for cardiovascular (CV) morbidity. The Reducing Air Pollution in Detroit Intervention Study (RAPIDS) was designed to evaluate PM2.5 exposure reduction and CV health improvement. We enrolled 40 participants from a low-income senior-citizen residential facility in Midtown Detroit, Michigan for a randomized blinded crossover in-home air filtration intervention. New insights are anticipated regarding (1) the effectiveness of economical LE filters and HE filters for reducing personal PM2.5 exposures and improving CV health, and (2) which outdoor sources and their associated CV health effects are most responsive to filtration. Co-investigators on this project include Drs. Robert Brook, Sara Adar, and Catherine Spino from University of Michigan; and Dr. Rosemary Ziemba at Community Health Nursing.