Toxicological Evidence for Health Effects from Inhaled Particulate Pollution: Does it Support the Human Experience?

Abstract

The fine size mode of ambient particulates, designated as PM-10, is a heterogeneous mixture that can vary in particle size and chemical composition, depending on geographical location, meteorology, and source emissions. While epidemiological studies indicate an association between ambient particulate air pollution exposure and increased human mortality and morbidity, the question remains as to biological plausibility. Individual components of PM-10 have been shown, in experimental studies, to produce what may be considered to be adverse health effects similar to those observed in humans. For example, diesel exhaust particles are associated with lung tumors, and acid sulfates are associated with airway hyperresponsiveness and alterations in mucociliary clearance. However, in most cases, exposure levels are well above those found in ambient air, and the relationship between results of toxicological assessments and human exposure scenarios is not always clear. Furthermore, in some cases, the chemical species resulting in adverse responses in toxicological studies are not always the same as those associated with effects in human population studies. Thus, while toxicological evidence clearly indicates the ability of certain ambient particles to induce increased morbidity in laboratory studies, the responsible chemical species have not been definitively delineated.