Polina B. Maciejczyk

Air pollution is a major environmental risk to health. Air pollution has been estimated to cause 6.7 million premature deaths worldwide annually (GBD, 2019). Fine Particulate Matter (PM2.5) is believed to be the largest contributor to the adverse health effects caused by air pollution, but the most toxic PM2.5 constituents and/or sources have not been definitively determined. In this chapter, we review the relevant scientific literature providing insights on health-related effects caused by inhalation of particulate metals, and their potential causal pathways. Based on both the available epidemiologic and toxicological evidence, we focus on the individual properties of metals commonly found in PM2.5 air pollution and their concentrations, sources, and adverse health effects. We also assess the possible involvement of metals in emerging occurrences of clusters of acute lung injury and mortality among e-cigarette users, as well consider the implications of particulate metals exposure effects to climate change mitigation efforts. While no single constituent is identifiable as causal to date, a central role by metals derived from fossil fuel combustion, in combination with acidic sulfur, is noted. In the future, with more ambient PM2.5 speciation monitoring, additional ambient source apportionment modeling, and additional toxicological studies involving PM2.5 component analyses (including of constituents, chemical form, and source-specific mixtures), the roles of specific metals and their coconstituent mixtures within PM can be expected to become clearer.

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.