Serious illness and injury following the September 11, 2001 (9/11) attacks on the World Trade Center (WTC) affects thousands of responders who worked on the WTC rescue and recovery effort. During this time, these individuals sustained exposure to a vast array of environmental toxins and physical hazards. The population of survivors presents a unique opportunity to rigorously examine the effects of inhaled particulate matter on risk of persistent pulmonary and chronic cardiopulmonary disease.