Effects of Subchronic Exposures to Concentrated Ambient Particles (CAPs) in Mice: I. Introduction, Objectives, and Experimental Plan

Abstract

This subchronic (6-mo) inhalation study of the effects of concentrated ambient air fine particulate matter (PM_2.5) in normal mice (C57) and a murine model of humans with an advanced level of aortic plaque (ApoE^−/−or ApoE^−/−LDLr^−/−) was designed to determine the presence and extent of a variety of health-related responses. The animals were exposed for 6 h/day, 5 days/wk during the spring and summer of 2003 to concentrations that were elevated 10-fold in Tuxedo, NY, a regional background site that is upwind and ∼50 km west-northwest of New York City. The average PM_2.5concentration during exposure was 110 μg/m³, and the long-term average was 19.7 μ g/m³. There were substantial daily variations in concentration, and we sought evidence both for the influence of peak exposures on acute responses and for the cumulative effects of the prolonged series of exposures. Acute responses were characterized in terms of: (1) short-term electrocardiographic (EKG), core body temperature, and physical activity differences between PM and sham-exposed mice; and (2) in vitrotoxicity of a simultaneously collected PM_2.5sample to lung epithelial cells. Cumulative responses to PM_2.5were characterized in terms of changes in heart rate, heart-rate variability, heart-rate variance, aortic plaque density, genetic marker expression, and brain cell distributions. There were no significant changes in the normal mice. The nature and extent of the exposure-related responses that were seen in the ApoE^−/−as well as ApoE^−/−LDLr^−/−mice are described in the articles that follow in this special issue of Inhalation Toxicology.