Metals and air pollution

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.