Safety assessment of continuous glass filaments used in eclipse

Our plain-English summary of Safety assessment of continuous glass filaments used in eclipse, by J.E. Swauger, J.W. Foy (Inhalation Toxicology, 2000).

The study

• Authors: J.E. Swauger, J.W. Foy
• Journal: Inhalation Toxicology
• Published: 2000;12(11):1071-84
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Eclipse is a cigarette that produces smoke by primarily heating, rather than burning, tobacco. The Eclipse heat source assembly employs a continuous filament glass mat jacket to insulate the heat source. The glass mat insulator is composed of continuous glass filaments and a binder. The purpose of this article is to address the potential toxicological significance of the continuous glass filaments under the conditions of intended use. Transfer data and the unique physical characteristics of the filaments demonstrate that significant exposure of the smoker will not occur. The available environmental survey data clearly demonstrate that Eclipse smokers are extremely unlikely to be exposed to continuous glass filaments at a level that represents a biologically significant increase over background exposure to glass fibers. The chemical composition of the continuous glass filaments used in Eclipse is generally similar to C-glass fiber compositions such as MMVF 11 that have failed to produce either tumors or fibrosis in chronic inhalation studies conducted in rats. In vitro dissolution data demonstrate that the continuous glass filaments used in Eclipse are more soluble than biologically active fibers such as rock wool (MMVF 21) or asbestos. However, the continuous glass filaments used in Eclipse were not as soluble in simulated extracellular lung fluid as representative C-glass fibers (MMVF 10 and MMVF 11). In brief, exposure of Eclipse smokers to continuous glass filaments is extremely unlikely to occur at a level that may be construed to be of biological significance.

In plain English

This review and safety assessment examined the continuous glass filaments insulating the heat source of Eclipse, an R. J. Reynolds Tobacco Company cigarette that mainly heats rather than burns tobacco. Transfer studies at R. J. Reynolds reported a maximum of 0.143 filaments per cigarette entering mainstream smoke under exaggerated machine smoking. Assuming all transferred filaments were respirable, the authors calculated that a one-pack-a-day smoker would be exposed to at most 2.86 filaments daily, about 0.011 to 0.72% of estimated non-workplace background glass fiber exposure. For filaments of the specified 9500 µm length and 8.5 µm mean diameter, they calculated aerodynamic diameters of about 53 µm or 40.2 µm, depending on orientation. Filaments recovered from smoke, about 850 µm long, gave 42.9 µm or 33.5 µm. The authors noted that structures with aerodynamic diameters above 7 µm are generally considered unlikely to reach the deep lung. In laboratory tests, the filaments were less soluble than MMVF 10 and MMVF 11 glass fibers but more soluble than rock wool or crocidolite asbestos. The authors concluded that Eclipse smokers were extremely unlikely to be exposed at a biologically significant level.

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: Review and safety assessment, drawing on earlier transfer, dissolution, animal and epidemiological studies, plus the authors' own exposure and particle-size calculations
• Who was studied: No human subjects. The subject was the glass mat insulator in Eclipse cigarettes, made by R. J. Reynolds Tobacco Company (RJRT), with exposure estimated for a hypothetical 1-pack/day smoker
• Exposure: Continuous glass filaments (a man-made vitreous fiber) with a mean diameter of 8.5 µm (range 5.5 to 14 µm), chopped to 9.5 mm and made into a mat. In dissolution tests they were compared with MMVF 10 and MMVF 11 glass fibers, MMVF 21 rock wool and crocidolite
• Main results:
  • Studies conducted at RJRT (Higuchi et al.), not this article, reported a maximum of 0.143 filaments per cigarette transferred to Eclipse mainstream smoke under exaggerated smoking conditions
  • The authors calculated that a 1-pack/day smoker would be exposed to a maximum of 2.86 filaments per day. This was a calculated estimate, not a measured dose, and it assumed that 100% of transferred fibers were respirable. It equals approximately 0.011 to 0.72% of estimated nonoccupational background exposure of 400 to 26,000 glass fibers per day
  • The authors calculated aerodynamic diameters for filaments at the specified 9500 µm length and 8.5 µm mean diameter: about 53 µm (parallel; range 35 to 84.4 µm) or 40.2 µm (perpendicular; range 26.7 to 64.2). They noted that structures with aerodynamic diameters above 7 µm are generally accepted as unlikely to reach the pulmonary region
  • Filaments recovered from Eclipse smoke condensate (Higuchi et al., 2000a) averaged approximately 850 µm long. The authors calculated that this length gives aerodynamic diameters of 42.9 µm (parallel) or 33.5 µm (perpendicular). For a worst-case broken filament (5.5 µm diameter, 16.5 µm long), they calculated about 13 µm
  • Based on a maximum deposition rate of 5%, the authors estimated that at most 0.143 filaments per day could potentially reach the lung of a 1-pack/day smoker
  • In an in vitro dissolution comparison (Foy & Swauger, 2000), the estimated dissolution rates were: MMVF 10, 394 ng/cm2/h; MMVF 11, 105; Eclipse filament, 35; MMVF 21 rock wool, 15; crocidolite, 1
  • The authors described the chemical composition of the Eclipse filaments as generally similar to C-glass fibers such as MMVF 11
  • The authors disputed a separate study (Pauly et al.) that observed filaments on Eclipse filters. They stated that the displacement rate implied by that study (about 0.8 filaments per cigarette) was more than six times the transfer rate seen in the Higuchi studies
• The authors' conclusion: The authors concluded that exposure of Eclipse smokers to continuous glass filaments is extremely unlikely to occur at a level of biological significance

Topics

Medical terms in this study, explained in our Lexicon: Insulator, Background Exposure, Fibrosis.

Related studies

• Cigarette smoke increases amosite asbestos fiber binding to the surface of tracheal epithelial cells — A. Churg, J. Sun, et al. (1998)
• Lung inflammation caused by inhaled toxicants: a review — J. Wong, B.E. Magun, et al. (2016)
• Effects of cigarette smoke exposure on retention of asbestos fibers in various morphologic compartments of the guinea pig lung — A. Churg, V. Tron, et al. (1987)
• Efficacy, Safety, and Cost-Minimization Analysis of Continuous Infusion of Low-Dose Gemcitabine Plus Cisplatin in Patients With Unresectable Malignant Pleural Mesothelioma — O. Arrieta, W. Muñoz-Montaño, et al. (2021)
• Man-made mineral fiber hazardous properties assessment using transgenic rodents: example of glass fiber testing — M.C. Bottin, J.C. Vigneron, et al. (2003)
• Effects of cigarette smoke and asbestos on airway, vascular and mesothelial cell proliferation — H. Sekhon, J. Wright, et al. (1995)

Browse more research in Inhalation Toxicology, or return to medical research.