Deposition of Air Pollution-Derived Magnetic Nanoparticles in Human Kidney Revealed by High-Resolution Microstructural Characterization

Exposure to air pollutants, especially fine particulate matter (PM_2.5), has been recognized as a major contributor to the increasing prevalence of kidney diseases. However, until now, evidence for the translocation of airborne nanoparticles (NPs) in the human kidney has been lacking, hindering the understanding of the relationships between PM_2.5 exposure and kidney diseases. Here, we report the discovery and analysis of airborne magnetite nanoparticles in human kidney stones (with mass concentrations ranging from 363 to 740 ng/g dry tissue weight) by high-resolution microstructural characterization. Notably, we established a methodology for highly selective extraction and accurate characterization of distinctive magnetite NPs and identified the abundant presence of these NPs with a distinctive core-shell structure of Fe₃O₄/SiO₂ in both kidney stones and human blood. We demonstrate that such distinctive core-shell magnetite NPs are indicative of a coal-burning source. Hence, magnetite NPs deposited in the human kidneys in this study area most likely derived from air pollution emissions from coal-fired power plants and were transported via blood circulation to the kidney. Our results provide compelling evidence for understanding the systemic health risks of exposure to nanoparticulate, Fe-bearing air pollution and the associations observed between kidney diseases and PM_2.5 exposure.