Iron Speciation in Respirable Particulate Matter and Implications for Human Health

• Published in: Environmental science & technology Vol. 56; no. 11; pp. 7006 - 7016
• Main Authors: O’Day, Peggy A., Pattammattel, Ajith, Aronstein, Paul, Leppert, Valerie J., Forman, Henry Jay
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 07.06.2022
• Subjects: Abrasion; Air Pollutants - analysis; Air pollution; Air Pollution - analysis; Anthropogenic factors; Anthropogenic Impacts on the Atmosphere; breathing; Global health; Health risks; human health; Humans; Hydrogen peroxide; inflammation; Inhalation; Iron; Lewis acids; Mixtures; Organic carbon; Outdoor air quality; Oxidants; Oxidative stress; Oxidizing agents; Particulate emissions; Particulate matter; Particulate Matter - analysis; particulates; Public health; Reactive Oxygen Species; Respiration; risk; Speciation; technology; nanoparticles; inflammation; PM2.5; electron energy loss spectroscopy; Fenton reactions; iron; X-ray absorption spectroscopy; oxidative stress
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/acs.est.1c06962

Particulate matter (PM) air pollution poses a major global health risk, but the role of iron (Fe) is not clearly defined because chemistry at the particle–cell interface is often not considered. Detailed spectromicroscopy characterizations of PM2.5 samples from the San Joaquin Valley, CA identified major Fe-bearing components and estimated their relative proportions. Iron in ambient PM2.5 was present in spatially and temporally variable mixtures, mostly as Fe­(III) oxides and phyllosilicates, but with significant fractions of metallic iron (Fe(0)), Fe­(II,III) oxide, and Fe­(III) bonded to organic carbon. Fe(0) was present as aggregated, nm-sized particles that comprised up to ∼30% of the Fe spectral fraction. Mixtures reflect anthropogenic and geogenic particles subjected to environmental weathering, but reduced Fe in PM originates from anthropogenic sources, likely as abrasion products. Possible mechanistic pathways involving Fe­(0) particles and mixtures of Fe­(II) and Fe­(III) surface species may generate hydrogen peroxide and oxygen-centered radical species (hydroxyl, hydroperoxyl, or superoxide) in Fenton-type reactions. From a health perspective, PM mixtures with reduced and oxidized Fe will have a disproportionate effect in cellular response after inhalation because of their tendency to shuttle electrons and produce oxidants and electrophiles that induce inflammation and oxidative stress.