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Iron Speciation in Respirable Particulate Matter and Implications for Human Health
Peggy A O'Day1,2, Ajith Pattammattel1,3, Paul Aronstein2
1Life and Environmental Sciences Department and the Sierra Nevada Research Institute, University of California, Merced, California 95343, United States.
Environmental Science & Technology
|March 2, 2022
Summary
Air pollution from particulate matter (PM) is a global health risk. This study reveals that iron (Fe) in PM2.5, particularly metallic Fe(0), significantly contributes to health impacts by generating harmful reactive oxygen species.
Area of Science:
- Environmental Science
- Chemistry
- Toxicology
Background:
- Particulate matter (PM) air pollution is a significant global health concern.
- The specific role of iron (Fe) in PM's health effects is not fully understood, particularly regarding particle-cell interactions.
- Understanding iron speciation in PM is crucial for assessing its toxicological impact.
Purpose of the Study:
- To characterize the iron-bearing components in PM2.5 samples.
- To investigate the chemical forms and proportions of iron in ambient PM.
- To explore potential mechanisms by which iron in PM contributes to oxidative stress and inflammation.
Main Methods:
- Detailed spectromicroscopy characterizations of PM2.5 samples.
- Estimation of relative proportions of different iron species.
- Analysis of spatial and temporal variability of iron components.
Main Results:
- Identified diverse Fe-bearing components in PM2.5, including Fe(III) oxides, phyllosilicates, Fe(0), Fe(II,III) oxide, and Fe(III)-organic carbon complexes.
- Found significant fractions (up to ~30%) of metallic iron (Fe(0)) as aggregated nanoparticles.
- Observed that reduced Fe originates from anthropogenic sources and contributes to Fenton-type reactions generating reactive oxygen species.
Conclusions:
- The presence of metallic Fe(0) and mixed Fe(II)/Fe(III) species in PM2.5 can lead to the production of reactive oxygen and electrophilic species.
- These iron-derived species can induce inflammation and oxidative stress, exacerbating the health risks associated with inhaling PM.
- Considering the chemistry at the particle-cell interface, especially the role of reduced iron, is essential for a comprehensive understanding of PM's health impacts.
