Exposure to Concentrated Ambient Particles Does Not Affect Vascular Function in Patients with Coronary Heart Disease

Abstract

Exposure to fine particulate air pollution is associated with increased cardiovascular morbidity and mortality. We previously demonstrated that exposure to dilute diesel exhaust causes vascular dysfunction in humans. We conducted a study to determine whether exposure to ambient particulate matter causes vascular dysfunction. Twelve male patients with stable coronary heart disease and 12 age-matched volunteers were exposed to concentrated ambient fine and ultrafine particles (CAPs) or filtered air for 2 hr using a randomized, double-blind cross-over study design. We measured peripheral vascular vasomotor and fibrinolytic function, and inflammatory variables-including circulating leukocytes, serum C-reactive protein, and exhaled breath 8-isoprostane and nitrotyrosine-6-8 hr after both exposures. Particulate concentrations (mean +/- SE) in the exposure chamber (190+/-37 microg/m(3)) were higher than ambient levels (31+/-8 microg/m(3)) and levels in filtered air (0.5+/-0.4 microg/m(3); p<0.001). Chemical analysis of CAPs identified low levels of elemental carbon. Exhaled breath 8-isoprostane concentrations increased after exposure to CAPs (16.9+/-8.5 vs. 4.9+/-1.2 pg/mL, p<0.05), but markers of systemic inflammation were largely unchanged. Although there was a dose-dependent increase in blood flow and plasma tissue plasminogen activator release (p<0.001 for all), CAPs exposure had no effect on vascular function in either group. Despite achieving marked increases in particulate matter, exposure to CAPs--low in combustion-derived particles--did not affect vasomotor or fibrinolytic function in either middle-aged healthy volunteers or patients with coronary heart disease. These findings contrast with previous exposures to dilute diesel exhaust and highlight the importance of particle composition in determining the vascular effects of particulate matter in humans.