Dr Terry Gordon and colleagues at the New York University School of Medicine conducted an exploratory study to test the effects of exposure to PM derived from New York City air on the rodent cardiopulmonary system. They hypothesized that PM would have greater, possibly fatal, effects in animals with compromised cardiopulmonary function than in normal animals. Gordon and colleagues exposed animals for up to 6 hours to concentrated particles that ranged from approximately 150 to 900 µg/m3. They exposed normal rats and hamsters, rats injected with monocrotaline to induce right-heart hypertrophy and pulmonary hypertension, and hamsters with a genetic cardiomyopathy. The investigators evaluated changes in heart rate and electrocardiogram intervals, mechanical pulmonary function, and inflammatory parameters.