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. 2023 Jan-Dec;35(7-8):201-213.
doi: 10.1080/08958378.2023.2220737.

Natural mineral fibers: conducting inhalation toxicology studies - part A: Libby Amphibole aerosol generation and characterization method development

Anbo Wang  1 , Amit Gupta  2 , Michael D Grimm  1 , David T Pressburger  2 , Barney R Sparrow  2 , Jamie S Richey  2 , John R Shaw  2 , Karen E Elsass  1 , Georgia K Roberts  3 , Pei-Li Yao  3 , Matthew D Stout  3 , Benjamin J Ellis  4 , Robyn L Ray  4
Affiliations

Natural mineral fibers: conducting inhalation toxicology studies - part A: Libby Amphibole aerosol generation and characterization method development

Anbo Wang et al. Inhal Toxicol. 2023 Jan-Dec.

Abstract

Background: Asbestos has been classified as a human carcinogen, and exposure may increase the risk of diseases associated with impaired respiratory function. As the range of health effects and airborne concentrations that result in health effects across asbestos-related natural mineral fiber types are not fully understood, the National Institute of Environmental Health Sciences has established a series of research studies to characterize hazards of natural mineral fibers after inhalation exposure. This paper presents the method development work of this research project.

Results: A prototype nose-only exposure system was fabricated to explore the feasibility of generating natural mineral fiber aerosol for in vivo inhalation toxicity studies. The prototype system consisted of a slide bar aerosol generator, a distribution/delivery system and an exposure carousel. Characterization tests conducted using Libby Amphibole 2007 (LA 2007) demonstrated the prototype system delivered stable and controllable aerosol concentration to the exposure carousel. Transmission electron microscopy (TEM) analysis of aerosol samples collected at the exposure port showed the average fiber length and width were comparable to the bulk LA 2007. TEM coupled with energy dispersive spectrometry (EDS) and selected area electron diffraction (SAED) analysis further confirmed fibers from the aerosol samples were consistent with the bulk LA 2007 chemically and physically.

Conclusions: Characterization of the prototype system demonstrated feasibility of generating LA 2007 fiber aerosols appropriate for in vivo inhalation toxicity studies. The methods developed in this study are suitable to apply to a multiple-carousel exposure system for a rat inhalation toxicity testing using LA 2007.

Keywords: Asbestos; Libby amphibole; aerosol generation; fiber; inhalation toxicology.

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Conflict of interest statement

Competing interests

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Digital Image of Bulk LA 2007.
Fig. 2
Fig. 2
Schematic of the Prototype Asbestos Aerosol Nose-Only Exposure System.
Fig. 3
Fig. 3
Schematic Diagram of the Slide Bar Aerosol Generator (Top Schematic: slide bar in fill position; Bottom Schematic: slide bar in deliver position)
Fig. 4
Fig. 4
Three-Tier 24-Port Nose-Only Exposure Carousel.
Fig. 5
Fig. 5
Representative Fiber Length Distributions. Top plot: result of one aerosol sample as an example. Bottom plot: result of one bulk LA 2007 material sample as an example.
Fig. 6
Fig. 6
Representative Fiber Width Distributions. Top plot: result of one aerosol sample as an example. Bottom plot: result of one bulk LA 2007 material sample as an example.
Fig. 7
Fig. 7
Representative TEM Images of LA 2007 Fibers - Aerosol Samples. Scale Bar is 800 nm for all photos.
Fig. 8
Fig. 8
Representative TEM Images of LA 2007 Fibers - Bulk Test Material Scale Bar is 500 nm for all photos.
Fig. 9
Fig. 9
Representative SAED Images. Top two scans were from aerosol samples. The bottom two scans were from bulk LA 2007. Scale bar is 0.2 1/Å for all scans
Fig. 10
Fig. 10
Representative EDS Spectra. The top three spectra were from aerosol samples collected on Day 0 (A), Day 2 (B), and Day 4 (C). The bottom spectra was from a bulk LA 2007 sample.
See this image and copyright information in PMC

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