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Magnetic and microscopic investigation of airborne iron oxide nanoparticles in the London Underground

Particulate matter (PM) concentration levels in the London Underground (LU) are higher than London background levels and beyond World Health Organization (WHO) defined limits. Wheel, track, and brake abrasion are the primary sources of particulate matter, producing predominantly Fe-rich particles th...

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Autores principales: Sheikh, H. A., Tung, P. Y., Ringe, E., Harrison, R. J.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Nature Publishing Group UK 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9755232/
https://www.ncbi.nlm.nih.gov/pubmed/36522360
http://dx.doi.org/10.1038/s41598-022-24679-4
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author Sheikh, H. A.
Tung, P. Y.
Ringe, E.
Harrison, R. J.
author_facet Sheikh, H. A.
Tung, P. Y.
Ringe, E.
Harrison, R. J.
author_sort Sheikh, H. A.
collection PubMed
description Particulate matter (PM) concentration levels in the London Underground (LU) are higher than London background levels and beyond World Health Organization (WHO) defined limits. Wheel, track, and brake abrasion are the primary sources of particulate matter, producing predominantly Fe-rich particles that make the LU microenvironment particularly well suited to study using environmental magnetism. Here we combine magnetic properties, high-resolution electron microscopy, and electron tomography to characterize the structure, chemistry, and morphometric properties of LU particles in three dimensions with nanoscale resolution. Our findings show that LU PM is dominated by 5–500 nm particles of maghemite, occurring as 0.1–2 μm aggregated clusters, skewing the size-fractioned concentration of PM artificially to larger sizes when measured with traditional monitors. Magnetic properties are largely independent of the PM filter size (PM(10), PM(4), and PM(2.5)), and demonstrate the presence of superparamagnetic (< 30 nm), single-domain (30–70 nm), and vortex/pseudo-single domain (70–700 nm) signals only (i.e., no multi-domain particles > 1 µm). The oxidized nature of the particles suggests that PM exposure in the LU is dominated by resuspension of aged dust particles relative to freshly abraded, metallic particles from the wheel/track/brake system, suggesting that periodic removal of accumulated dust from underground tunnels might provide a cost-effective strategy for reducing exposure. The abundance of ultrafine particles identified here could have particularly adverse health impacts as their smaller size makes it possible to pass from lungs to the blood stream. Magnetic methods are shown to provide an accurate assessment of ultrafine PM characteristics, providing a robust route to monitoring, and potentially mitigating this hazard.
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spelling pubmed-97552322022-12-17 Magnetic and microscopic investigation of airborne iron oxide nanoparticles in the London Underground Sheikh, H. A. Tung, P. Y. Ringe, E. Harrison, R. J. Sci Rep Article Particulate matter (PM) concentration levels in the London Underground (LU) are higher than London background levels and beyond World Health Organization (WHO) defined limits. Wheel, track, and brake abrasion are the primary sources of particulate matter, producing predominantly Fe-rich particles that make the LU microenvironment particularly well suited to study using environmental magnetism. Here we combine magnetic properties, high-resolution electron microscopy, and electron tomography to characterize the structure, chemistry, and morphometric properties of LU particles in three dimensions with nanoscale resolution. Our findings show that LU PM is dominated by 5–500 nm particles of maghemite, occurring as 0.1–2 μm aggregated clusters, skewing the size-fractioned concentration of PM artificially to larger sizes when measured with traditional monitors. Magnetic properties are largely independent of the PM filter size (PM(10), PM(4), and PM(2.5)), and demonstrate the presence of superparamagnetic (< 30 nm), single-domain (30–70 nm), and vortex/pseudo-single domain (70–700 nm) signals only (i.e., no multi-domain particles > 1 µm). The oxidized nature of the particles suggests that PM exposure in the LU is dominated by resuspension of aged dust particles relative to freshly abraded, metallic particles from the wheel/track/brake system, suggesting that periodic removal of accumulated dust from underground tunnels might provide a cost-effective strategy for reducing exposure. The abundance of ultrafine particles identified here could have particularly adverse health impacts as their smaller size makes it possible to pass from lungs to the blood stream. Magnetic methods are shown to provide an accurate assessment of ultrafine PM characteristics, providing a robust route to monitoring, and potentially mitigating this hazard. Nature Publishing Group UK 2022-12-15 /pmc/articles/PMC9755232/ /pubmed/36522360 http://dx.doi.org/10.1038/s41598-022-24679-4 Text en © The Author(s) 2022 https://creativecommons.org/licenses/by/4.0/Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) .
spellingShingle Article
Sheikh, H. A.
Tung, P. Y.
Ringe, E.
Harrison, R. J.
Magnetic and microscopic investigation of airborne iron oxide nanoparticles in the London Underground
title Magnetic and microscopic investigation of airborne iron oxide nanoparticles in the London Underground
title_full Magnetic and microscopic investigation of airborne iron oxide nanoparticles in the London Underground
title_fullStr Magnetic and microscopic investigation of airborne iron oxide nanoparticles in the London Underground
title_full_unstemmed Magnetic and microscopic investigation of airborne iron oxide nanoparticles in the London Underground
title_short Magnetic and microscopic investigation of airborne iron oxide nanoparticles in the London Underground
title_sort magnetic and microscopic investigation of airborne iron oxide nanoparticles in the london underground
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9755232/
https://www.ncbi.nlm.nih.gov/pubmed/36522360
http://dx.doi.org/10.1038/s41598-022-24679-4
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