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Elucidating the Impact of Inhaled Micro-, Nanoplastics from Surgical Face Masks in vitro / LEWIS HODGETTS

Swansea University Author: LEWIS HODGETTS

  • E-Thesis – open access under embargo until: 15th October 2025

Abstract

The use of surgical face masks is commonplace throughout medical and occupational settings, but their use was extended to the public during the COVID-19 pandemic, resulting in an influx of manufacture and wastage. These masks are predominantly synthesised from polypropylene (PP), but the complete ma...

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Published: Swansea, Wales, UK 2024
Institution: Swansea University
Degree level: Master of Research
Degree name: MSc by Research
Supervisor: Clift, Martin J. D. ; Wright, Stephanie ; Doak, Shareen H.
URI: https://cronfa.swan.ac.uk/Record/cronfa68099
first_indexed 2024-10-29T13:02:23Z
last_indexed 2024-11-25T14:21:26Z
id cronfa68099
recordtype RisThesis
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These single-use masks are known to shed micro,-nanoplastic (MNP) debris directly into the respiratory system, and into the environment upon improper disposal. Plastics in the environment degrade into MNPs over time via several processes, eventually gaining the potential to become airborne. The scenarios of how these mask MNPs could be inhaled, were represented in this project by the use of the innermost layer of mask only (white), and the indirect environmental route; an amalgam of all three mask layers (blue). Despite much focus on the environmental impact of MNPs, the effects these particles could have to human health following inhalation, is largely unknown. Therefore, the aim of this project was to determine the toxicity of PP MNPs, and MNPs derived from face masks representative of two different inhalation exposure scenarios, using an advanced in vitro approach. All synthesized MNPs used a top-down approach; the cryogenic milling of commercial PP powder, 55-75 &#x3BC;m in diameter (purchased from Goonvean Fibres Ltd.), into particles &#x2264;5 &#x3BC;m in diameter. Surgical masks MNPs were synthesized via repeated cryotome slicing. All MNP were characterised via pyrolysis-GC-MS, dynamic light scattering and zeta potential, and further by SEM and STEM-EDX following aerosolisation. NCI-H441 type-II alveolar epithelial cells were cultured at the air-liquid interface, and were exposed to 0.5, 1.0 or 2.0 &#x3BC;g/cm2 of each MNP type for 24 hours. Carbon black (Printex 90) was used as positive particle control. Endpoint analyses of cell death (trypan blue exclusion), barrier integrity (dextran blue), pro-inflammatory response (IL-1&#x3B2;/IL-6/IL-8) and genotoxicity (mononucleate micronucleus) were conducted, alongside Confocal LSM microscopy. STEM-EDX presented each MNP sample to consist predominantly of sodium and chlorine, with lesser expression of carbon, oxygen and titanium. Pyrolysis-GC-MS confirmed dominance of PP content in the tested MNPs, alongside the presence of additives, although this requires further investigation. Both mask MNPs presented significant concentration-dependent increases to IL-8 production and mononucleated micronucleus formation, peaking at 1.0 &#x3BC;g/cm2, but then decreasing at 2.0 &#x3BC;g/cm2 across all respirable MNP samples. Respirable PP MNPs also displayed similar trends to the mask MNPs, but these were not statistically significant findings. Current data therefore suggests that inhalation of MNPs do have the potential to produce hazardous responses to alveolar models in vitro. Future developments should improve on the realism of the model by the incorporation of immune cell co-culturing. 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spelling 2024-10-29T13:21:57.0022371 v2 68099 2024-10-29 Elucidating the Impact of Inhaled Micro-, Nanoplastics from Surgical Face Masks in vitro 06af263ca9c219f2fe679d711d3c1e0c LEWIS HODGETTS LEWIS HODGETTS true false 2024-10-29 The use of surgical face masks is commonplace throughout medical and occupational settings, but their use was extended to the public during the COVID-19 pandemic, resulting in an influx of manufacture and wastage. These masks are predominantly synthesised from polypropylene (PP), but the complete material list is unknown, and their exact composition varies between suppliers. These single-use masks are known to shed micro,-nanoplastic (MNP) debris directly into the respiratory system, and into the environment upon improper disposal. Plastics in the environment degrade into MNPs over time via several processes, eventually gaining the potential to become airborne. The scenarios of how these mask MNPs could be inhaled, were represented in this project by the use of the innermost layer of mask only (white), and the indirect environmental route; an amalgam of all three mask layers (blue). Despite much focus on the environmental impact of MNPs, the effects these particles could have to human health following inhalation, is largely unknown. Therefore, the aim of this project was to determine the toxicity of PP MNPs, and MNPs derived from face masks representative of two different inhalation exposure scenarios, using an advanced in vitro approach. All synthesized MNPs used a top-down approach; the cryogenic milling of commercial PP powder, 55-75 μm in diameter (purchased from Goonvean Fibres Ltd.), into particles ≤5 μm in diameter. Surgical masks MNPs were synthesized via repeated cryotome slicing. All MNP were characterised via pyrolysis-GC-MS, dynamic light scattering and zeta potential, and further by SEM and STEM-EDX following aerosolisation. NCI-H441 type-II alveolar epithelial cells were cultured at the air-liquid interface, and were exposed to 0.5, 1.0 or 2.0 μg/cm2 of each MNP type for 24 hours. Carbon black (Printex 90) was used as positive particle control. Endpoint analyses of cell death (trypan blue exclusion), barrier integrity (dextran blue), pro-inflammatory response (IL-1β/IL-6/IL-8) and genotoxicity (mononucleate micronucleus) were conducted, alongside Confocal LSM microscopy. STEM-EDX presented each MNP sample to consist predominantly of sodium and chlorine, with lesser expression of carbon, oxygen and titanium. Pyrolysis-GC-MS confirmed dominance of PP content in the tested MNPs, alongside the presence of additives, although this requires further investigation. Both mask MNPs presented significant concentration-dependent increases to IL-8 production and mononucleated micronucleus formation, peaking at 1.0 μg/cm2, but then decreasing at 2.0 μg/cm2 across all respirable MNP samples. Respirable PP MNPs also displayed similar trends to the mask MNPs, but these were not statistically significant findings. Current data therefore suggests that inhalation of MNPs do have the potential to produce hazardous responses to alveolar models in vitro. Future developments should improve on the realism of the model by the incorporation of immune cell co-culturing. To improve endpoint analysis, the introduction of oxidative stress evaluation and gene expression is necessary, in addition to the validation of a suitable genotoxic assay protocol for NCI-H441 cells. E-Thesis Swansea, Wales, UK Inhalation, in vitro, Microplastic, Nanoplastic, Air Pollution, Toxicology, Characterisation, Polypropylene, Mask 15 10 2024 2024-10-15 ORCiD identifier: https://orcid.org/0009-0003-9003-0923 COLLEGE NANME COLLEGE CODE Swansea University Clift, Martin J. D. ; Wright, Stephanie ; Doak, Shareen H. Master of Research MSc by Research 2024-10-29T13:21:57.0022371 2024-10-29T12:53:10.5389494 Faculty of Medicine, Health and Life Sciences Swansea University Medical School - Biomedical Science LEWIS HODGETTS 1 Under embargo Under embargo 2024-10-29T13:15:55.7634659 Output 5331512 application/pdf E-Thesis – open access true 2025-10-15T00:00:00.0000000 Copyright: The author, Lewis James Hodgetts, 2024. Licensed under the terms of a Creative Commons Attribution-Only (CC-BY) license. Third party content is excluded for use under the license terms. true eng https://creativecommons.org/licenses/by/4.0/deed.en
title Elucidating the Impact of Inhaled Micro-, Nanoplastics from Surgical Face Masks in vitro
spellingShingle Elucidating the Impact of Inhaled Micro-, Nanoplastics from Surgical Face Masks in vitro
LEWIS HODGETTS
title_short Elucidating the Impact of Inhaled Micro-, Nanoplastics from Surgical Face Masks in vitro
title_full Elucidating the Impact of Inhaled Micro-, Nanoplastics from Surgical Face Masks in vitro
title_fullStr Elucidating the Impact of Inhaled Micro-, Nanoplastics from Surgical Face Masks in vitro
title_full_unstemmed Elucidating the Impact of Inhaled Micro-, Nanoplastics from Surgical Face Masks in vitro
title_sort Elucidating the Impact of Inhaled Micro-, Nanoplastics from Surgical Face Masks in vitro
author_id_str_mv 06af263ca9c219f2fe679d711d3c1e0c
author_id_fullname_str_mv 06af263ca9c219f2fe679d711d3c1e0c_***_LEWIS HODGETTS
author LEWIS HODGETTS
author2 LEWIS HODGETTS
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publishDate 2024
institution Swansea University
college_str Faculty of Medicine, Health and Life Sciences
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hierarchy_top_id facultyofmedicinehealthandlifesciences
hierarchy_top_title Faculty of Medicine, Health and Life Sciences
hierarchy_parent_id facultyofmedicinehealthandlifesciences
hierarchy_parent_title Faculty of Medicine, Health and Life Sciences
department_str Swansea University Medical School - Biomedical Science{{{_:::_}}}Faculty of Medicine, Health and Life Sciences{{{_:::_}}}Swansea University Medical School - Biomedical Science
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description The use of surgical face masks is commonplace throughout medical and occupational settings, but their use was extended to the public during the COVID-19 pandemic, resulting in an influx of manufacture and wastage. These masks are predominantly synthesised from polypropylene (PP), but the complete material list is unknown, and their exact composition varies between suppliers. These single-use masks are known to shed micro,-nanoplastic (MNP) debris directly into the respiratory system, and into the environment upon improper disposal. Plastics in the environment degrade into MNPs over time via several processes, eventually gaining the potential to become airborne. The scenarios of how these mask MNPs could be inhaled, were represented in this project by the use of the innermost layer of mask only (white), and the indirect environmental route; an amalgam of all three mask layers (blue). Despite much focus on the environmental impact of MNPs, the effects these particles could have to human health following inhalation, is largely unknown. Therefore, the aim of this project was to determine the toxicity of PP MNPs, and MNPs derived from face masks representative of two different inhalation exposure scenarios, using an advanced in vitro approach. All synthesized MNPs used a top-down approach; the cryogenic milling of commercial PP powder, 55-75 μm in diameter (purchased from Goonvean Fibres Ltd.), into particles ≤5 μm in diameter. Surgical masks MNPs were synthesized via repeated cryotome slicing. All MNP were characterised via pyrolysis-GC-MS, dynamic light scattering and zeta potential, and further by SEM and STEM-EDX following aerosolisation. NCI-H441 type-II alveolar epithelial cells were cultured at the air-liquid interface, and were exposed to 0.5, 1.0 or 2.0 μg/cm2 of each MNP type for 24 hours. Carbon black (Printex 90) was used as positive particle control. Endpoint analyses of cell death (trypan blue exclusion), barrier integrity (dextran blue), pro-inflammatory response (IL-1β/IL-6/IL-8) and genotoxicity (mononucleate micronucleus) were conducted, alongside Confocal LSM microscopy. STEM-EDX presented each MNP sample to consist predominantly of sodium and chlorine, with lesser expression of carbon, oxygen and titanium. Pyrolysis-GC-MS confirmed dominance of PP content in the tested MNPs, alongside the presence of additives, although this requires further investigation. Both mask MNPs presented significant concentration-dependent increases to IL-8 production and mononucleated micronucleus formation, peaking at 1.0 μg/cm2, but then decreasing at 2.0 μg/cm2 across all respirable MNP samples. Respirable PP MNPs also displayed similar trends to the mask MNPs, but these were not statistically significant findings. Current data therefore suggests that inhalation of MNPs do have the potential to produce hazardous responses to alveolar models in vitro. Future developments should improve on the realism of the model by the incorporation of immune cell co-culturing. To improve endpoint analysis, the introduction of oxidative stress evaluation and gene expression is necessary, in addition to the validation of a suitable genotoxic assay protocol for NCI-H441 cells.
published_date 2024-10-15T08:19:27Z
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