Does inhalation of ultrafine particles cause pulmonary vascular effects in humans?

Inhalation of ambient particulate matter increases the risk of cardiovascular disease. Clinical studies play an important role in elucidating mechanisms for pollutant effects, and in establishing ambient air quality standards. Ultrafine particles (UFP; diameter <100 nm) may be important in the cardiovascular effects of ambient PM, yet there are few clinical studies of UFP health effects. Our laboratory has developed an exposure facility for clinical studies of laboratory-generated UFP. We confirmed previous predictions that UFP <50 nm in diameter deposit in the respiratory tract with a high efficiency, and have shown that exercise or the presence of asthma further increases UFP deposition. UFP exposure with exercise reduced expression of selected adhesion molecules on blood leukocytes, and also decreased the pulmonary diffusing capacity for carbon monoxide. These findings are best explained by UFP effects on pulmonary vascular function. These findings provide a possible mechanism by which inhalation of UFP may contribute to cardiopulmonary health effects in susceptible people.