ABSTRACT
Occupational and environmental exposures to inhaled fibers and particu-
lates can result in the development of lung disease. In this regard, recent
epidemiological studies have demonstrated an association between elevated
levels of particulate urban air pollution and adverse health effects in humans; particularly in susceptible individuals with pre-existing respiratory and
cardiovascular disease (1-3). The components of particulate matter in
urban air pollution have been characterized into three modes-namely,
ultrafine particulates (i.e., <0.1 mm diameter), fine particles (ranging from 0.1 mm to 2.5 mm), and coarse particles (>2.5 mm). Ultrafine particles contribute very little to the overall mass, but are disproportionate in particle
number. Epidemiological studies suggest that ultrafine and fine-mode parti-
cles are better correlated with adverse health effects when compared to coarse particles (4). Oberdorster (5) has postulated that urban source ultra-
fine particles, consisting of a carbonaceous core with surface attached inor-
ganic and organic materials, are the major cause of adverse health effects in
compromised individuals during high air pollution days.
