Passage of Inhaled Particles Into the Blood Circulation in Humans

Abstract
Background — Pollution by particulates has been consistently associated with increased cardiovascular morbidity and mortality. However, the mechanisms responsible for these effects are not well-elucidated. Methods and Results — To assess to what extent and how rapidly inhaled pollutant particles pass into the systemic circulation, we measured, in 5 healthy volunteers, the distribution of radioactivity after the inhalation of “Technegas,” an aerosol consisting mainly of ultrafine 99m Technetium-labeled carbon particles (99m Tc, ie, pertechnetate, there was also a species corresponding to particle-bound 99m Tc. Gamma camera images showed substantial radioactivity over the liver and other areas of the body. Conclusions — We conclude that inhaled 99m Tc-labeled ultrafine carbon particles pass rapidly into the systemic circulation, and this process could account for the well-established, but poorly understood, extrapulmonary effects of air pollution.