A Comparison of Studies on the Effects of Controlled Exposure to Fine, Coarse and Ultrafine Ambient Particulate Matter from a Single Location

Abstract

Particle size has been implicated by epidemiological and toxicological studies as an important determinant of the toxicity of ambient particulate matter (PM). In an effort to characterize the cardiovascular, hematological and pulmonary effects of different PM size fractions in humans, we have conducted controlled human exposures of normal volunteers to ultrafine-, fine- and coarse- fraction PM concentrated from ambient air in Chapel Hill, North Carolina. Healthy non-smoking male and female subjects between the ages of 18 and 35 participated in these studies. Exposures were undertaken with the use of particle concentrators fitted with size-selective outlets. These devices are capable of generating concentration factors between 10- and 20-fold over ambient levels. Cardiovascular endpoints measured include heart rate variability and T-wave alternans, as well as pulmonary function parameters. Subjects underwent bronchoscopy and bronchoalveolar lavage 18 hrs following exposure to PM or to clean air. Lavage fluids and blood samples were assayed for a battery of markers of hematological, cytotoxic and inflammatory injury. The design of these studies permits direct comparison of the effects of concentrated ambient PM as a function of particle size. The data to be presented reveal modest size fraction-dependent effects of concentrated PM exposure on cardiovascular, pulmonary and hematological parameters in normal adult human subjects. These findings have relevant implications for the design of future chamber studies and the role of particle size fraction in the adverse health effects of PM exposure in humans.