Size and Composition Matters: From Engineered Nanoparticles to Ambient Fine Particles

Air pollution is a complex mixture of gaseous, volatile, and particulate matter (PM) containing inorganic and organic species. There is now abundant evidence in epidemiological and toxicological studies that air pollution contributes to the development and exacerbation of diseases of respiratory, cardiovascular, and other organs, and associated mortality. Studies showed that equal masses of PM could induce disparate health effects, suggesting that particle sizes and components may be at fault. The fine and ultrafine PM is considered to be particularly important because the small particles can be easily inhaled. Possible biological mechanisms of action leading to adverse effects include the production of inflammatory mediators in the lung causing systemic inflammation, interaction with neural receptors causing interference with the central nervous system regulation of cardiovascular function, and particle translocation via the bloodstream to other organs. This chapter reviews whether some components of the PM mixture are of a greater public health concern than others, and presents compelling evidence that trace elements are most strongly linked to the adverse effects. Air pollution has wide-ranging and harmful effects on human health and is a major issue for the global community. Further research should explore the effects of source-specific PM with more advanced approaches to exposure modeling, measurements, and statistics, which would lead to more effective legislation and interventions for greater benefits to public health.