Integrative summary of the Third PM Colloquium

Research on human exposure to ambient air particulate matter (PM) reported on at the Third PM Colloquium indicates that the field is now moving beyond descriptive reports that focused largely on gravimetric concentrations of Phl in ambient air and in other microenvironments, and their associations w ith indices of short-term changes in rates of mortality and morbidity. Ther e is now a welcome shift in emphasis toward a more detailed analysis of PM exposures and dosimetry in terms of size-segregated PM fractions (PM10, PM2 .5, and ultrafines) and their chemical constituents, as well as toward biol ogical response measures. Such responses shed light on the underlying mecha nisms that account for both short- and long-term responses to ambient air P M and copollutants on the respiratory tract, the cardiovascular system, and immune function. Through both the formal presentations of research finding s and the opportunities provided for more informal discussions of mutual in terest, this Third Colloquium has enhanced opportunities for collaborative research that may be able to clarify the chain of events leading from pollu tion in the ambient air to adverse impacts on health and longevity.