Concentrated Ambient Ultrafine Particle Exposure Induces Cardiac Changes in Young Healthy Volunteers

Rationale: Exposure to ambient ultrafine particles has been associated with cardiopulmonary toxicity and mortality. Adverse effects specifically linked to ultrafine particles include loss of sympathovagal balance and altered hemostasis. Objectives: To characterize the effects of acute exposure to ambient ultrafine particles in young healthy humans. Methods: Nineteen healthy nonsmoking male and female subjects between the ages of 18 and 35 were exposed to filtered air or to an atmosphere in which captured ultrafine (<0.16 mu m) particles were concentrated by a factor of up to 20-fold over ambient levels with the use of particle concentrators fitted with size-selective outlets (ultrafine concentrated ambient particles [UFCAPs]). Subjects underwent bronchoalveolar lavage 18 hours after each exposure. Cardiovascular endpoints measured included pulmonary function, clinical chemistry, and hematological parameters, as well as heart rate variability and repolarization indices. Measurements and Main Results: Exposure to UFCAPs was statistically associated with an increase in frequency domain markers of heart rate variability, specifically indicative of elevated vagal input to the heart. Consistent with this finding were increases in the variance associated with the duration of the QT interval. In addition, UFCAP exposure resulted in a significant increase in blood levels of the fibrin degradation product D-dimer as well as a modest elevation in the inflammatory chemokine IL-8 recovered in the lavage fluid. Conclusions: These findings show mild inflammatory and prothrombic responses and are suggestive of alterations in cardiac repolarization induced by UFCAP inhalation.