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. 2023 Jan-Dec;35(7-8):214-229.
doi: 10.1080/08958378.2023.2220735.

Natural mineral fibers: conducting inhalation toxicology studies-part B: development of a nose-only exposure system for repeat-exposure in vivo study of Libby amphibole aerosol

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 B: development of a nose-only exposure system for repeat-exposure in vivo study of Libby amphibole aerosol

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

Abstract

Background: Exposure to asbestos is associated with malignant and nonmalignant respiratory disease. To strengthen the scientific basis for risk assessment on fibers, the National Institute of Environmental Health Sciences (NIEHS) has initiated a series of studies to address fundamental questions on the toxicology of naturally occurring asbestos and related mineral fibers after inhalation exposure. A prototype nose-only exposure system was previously developed and validated. The prototype system was expanded to a large-scale exposure system in this study for conducting subsequent in vivo rodent inhalation studies of Libby amphibole (LA) 2007, selected as a model fiber.

Results: The exposure system consisting of six exposure carousels was able to independently deliver stable LA 2007 aerosol to individual carousels at target concentrations of 0 (control group), 0.1, 0.3, 1, 3, or 10 mg/m3. A single aerosol generator was used to provide aerosol to all carousels to ensure that exposure atmospheres were chemically and physically similar, with aerosol concentration as the only major variable among the carousels. Transmission electron microscopy (TEM) coupled with energy dispersive spectrometry (EDS) and selected area electron diffraction (SAED) analysis of aerosol samples collected at the exposure ports indicated the fiber dimensions, chemical composition, and mineralogy were equivalent across exposure carousels and were comparable to the bulk LA 2007 material.

Conclusion: The exposure system developed is ready for use in conducting nose-only inhalation toxicity studies of LA 2007 in rats. The exposure system is anticipated to have applicability for the inhalation toxicity evaluation of other natural mineral fibers of concern.

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.
Exposure Suite Layout
Fig 2.
Fig 2.
Schematic Diagram of the Aerosol Exposure System
Fig 3.
Fig 3.
Representative Fiber Length Distributions. Top plot: One example of aerosol sample (1 mg/m3). Bottom plot: One example of bulk LA 2007 test material.
Fig 4.
Fig 4.
Representative Fiber Width Distributions Top plot: one example of aerosol sample (1 mg/m3). Bottom plot: one example of LA 2007 bulk material.
Fig 5.
Fig 5.
Representative TEM Images of LA 2007 Fibers Aerosol Samples. Scale Bar is 800 nm
Fig 6.
Fig 6.
Representative TEM Images of Fibers of LA 2007 Bulk Material. Scale Bar is 800 nm
Fig 7.
Fig 7.
Representative SAED Images The top two scans were from aerosol samples. The bottom two scans were from bulk LA 2007 test material. Scale bar is 0.2 1/Å for all scans
Fig 8.
Fig 8.
Representative EDS Spectra The top spectra were from an aerosol sample. The bottom spectra were from bulk LA 2007 test material.
Fig 9.
Fig 9.
Representative Mineral Composition Plots for LA 2007 Analyzed using EDS Top: representative plot for LA 2007 aerosol sample. Bottom: representative plot for bulk LA 2007.
See this image and copyright information in PMC

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