Airborne fiber particles: Types, size and concentration observed in Beijing

Our plain-English summary of Airborne fiber particles: Types, size and concentration observed in Beijing, by Y. Li, L. Shao, W. Wang, et al (The Science of the Total Environment, 2020).

The study

• Authors: Y. Li, L. Shao, W. Wang, M. Zhang, X. Feng, W. Li, D. Zhang
• Journal: The Science of the Total Environment
• Published: 2020;705:135967
• Cited by: 135 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Airborne fibers are of public concern because of their potential threat to the environment, however their physical and chemical properties are poorly understood. Fibers are defined as having an aspect ratio >3:1. Fiber particles were collected in the near surface air, surface deposited dust and building materials in Beijing. They were examined using analytical scanning electron microscopy. The particles were initially classified into two categories: organic and inorganic. Organic fibers comprised microplastic and natural organic fiber particles. Inorganic fibers were mainly man-made mineral fibers (MMMFs), asbestos (represented by chrysotile), calcium sulfate and metal fiber particles. Microplastic and MMMFs fibers were most abundant, accounting for 34.6% and 40.3% in total, respectively, followed by asbestos (7.8%), calcium sulfate (7.2%), metal fibers (5.6%) and natural organic fiber particles (4.5%). The number-concentration of these particles was about 16.7 × 10-3 fibers/ml at 1.5 m above the ground and about 14.1 × 10-3 fibers/ml at about 18 m, suggesting the particles were mainly derived from surface and were re-suspended. Approximately 80% of the airborne fiber were smaller than 20 μm in length, which is possibly the critical size for fiber particles to re-suspend into the air. Surface dust and construction sites were speculated to be the major contributors of the fiber particles.

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In plain English

The authors measured fibers in outdoor air in Beijing, China, using an electron microscope with elemental analysis. In October 2018 they collected two air filters at 1.5 m above ground (breathing height) and two on a building roof 18 m up, on a university campus. They also collected surface dust, and building materials from a nearby construction site. Fibers were sorted into microplastic, natural organic, man-made mineral fibers (MMMFs), asbestos (represented by chrysotile), calcium sulfate and metal types. At 1.5 m, total fibers averaged 16.7 × 10⁻³ fibers/ml, including asbestos at 1.4 × 10⁻³ fibers/ml (7.8%). MMMFs (40.3%) and microplastics (34.6%) were most common. On the roof, the total was 14.1 × 10⁻³ fibers/ml and asbestos was 0.9 × 10⁻³ fibers/ml (7.5%). Most airborne fibers were 5 to 20 μm long. Asbestos was also found in surface dust and in cement parts from old house roofs. The authors suggested building materials may release airborne asbestos and MMMFs. They wrote that asbestos may pose health risks, although the 1.5 m level was below a 2.2 × 10⁻³ fibers/ml standard they cited from WHO.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Environmental air-sampling and microscopy study: fibers in air filters, surface dust and building materials were counted and typed by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX)
• Who was studied: Outdoor air at a university campus (China University of Mining and Technology) in northwestern urban Beijing, October 2018. Four air filters were taken: two on a building roof at 18 m (RB) and two at 1.5 m (HRH, human respiratory height). Two ground-surface dustfall samples were taken. Building materials came from a construction site at Dongwangzhuang (DWZ) community.
• Exposure: Airborne fibers (longer than 5 μm, under 3 μm wide, length-to-width 3:1 or more) of several types: microplastic, natural organic, man-made mineral fibers (glass, rock wool), asbestos (represented by chrysotile), calcium sulfate and metal fibers
• Main results:
  • Roof site (18 m): total fiber concentration (geometric average) was 14.1 × 10⁻³ fibers/ml
  • Roof site (18 m): asbestos fibers were 0.9 × 10⁻³ fibers/ml
  • Roof site (18 m): asbestos made up 7.5% of fibers
  • Breathing-height site (1.5 m): total fiber concentration was 16.7 × 10⁻³ fibers/ml
  • Breathing-height site (1.5 m): MMMFs were 40.3%, microplastic fibers 34.6% and asbestos fibers 7.8% of fibers
  • Roof site: about 80% of fibers were 5 to 20 μm long
  • Breathing-height site: about 84% of fibers were 5 to 20 μm long
  • Surface dust contained microplastic fibers, asbestos fibers and MMMFs
  • About 70% of fibers in surface dust were 25 to 200 μm long
  • Cement-prefabricated parts from roofs of old houses at the construction site contained asbestos
  • The authors suggested that airborne asbestos and MMMFs may come from building materials
• The authors' conclusion: The authors wrote that asbestos fibers of 5 to 20 μm may pose health risks. They noted that the asbestos concentration at breathing height (1.4 × 10⁻³ fibers/ml) was lower than a standard of 2.2 × 10⁻³ fibers/ml, which they cited from WHO (1998).

Topics

Medical terms in this study, explained in our Lexicon: Aspect Ratio (Length-to-diameter ratio), Scanning Electron Microscopy (SEM), Mineral Fiber, Chrysotile, Settled Dust.

Related studies

• Airborne fiber concentration and size distribution of mineral fibers in area with serpentinite outcrops in Aichi prefecture, Japan — K. Sakai, N. Hisanaga, et al. (2001)
• Types, numbers, sizes, and distribution of mineral particles in the lungs of urban male cigarette smokers — A. Churg, B. Wiggs (1987)
• A meta-analysis of asbestos-related cancer risk that addresses fiber size and mineral type — D.W. Berman, K.S. Crump (2008)
• Airborne fiber size characterization in exposure estimation: Evaluation of a modified transmission electron microcopy protocol for asbestos and potential use for carbon nanotubes and nanofibers — J.M. Dement, E.D. Kuempel, et al. (2015)
• Relationship between lung asbestos fiber type and concentration and relative risk of mesothelioma. A case-control study — A.J. Rogers, J. Leigh, et al. (1991)
• Emission of airborne fibers from mechanically impacted asbestos-cement sheets and concentration of fibrous aerosol in the home environment in Upper Silesia, Poland — J.S. Pastuszka (2009)

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