Tremolite-actinolite fiber coatings of sub-nanometer silica-rich particles in lungs from deceased Quebec miners

Our plain-English summary of Tremolite-actinolite fiber coatings of sub-nanometer silica-rich particles in lungs from deceased Quebec miners, by M. Germine, J.H. Puffer (Toxicology and Industrial Health, 2020).

The study

• Authors: M. Germine, J.H. Puffer
• Journal: Toxicology and Industrial Health
• Published: 2020;36(3):146-152
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Tremolite-actinolite (TA) fibers from the lungs of deceased former Quebec mine workers were found to be coated with sub-nanometer particles. Qualitative chemical analyses were performed on the particles indicating that they were composed of silicon and oxygen. The crystal lattice structure of all amphibole minerals, including the TA series, is arranged as pairs of linear chains of SiO4 tetrahedra that are linked together to form double chains. Our observations of the TA fibers from miner's lungs, made using a high-resolution transmission electron microscope, indicated that the tetrahedral silica chains were progressively split, forming dispersed sub-nanometer particles. The non-tetrahedral sites were removed at the surface of the TA fibers, presumably by the oxidation process involved in attempted phagocytosis, which also resulted in fragmentation of the tetrahedral chains. It was found that the silicon-rich particles (SRPs) were variable in diameter, consistent with fragments formed from the splitting of the tetrahedral chains. The TA fibers from lungs displayed coatings and linear interior zones of SRP parallel to the planes of longitudinal fiber splitting. The literature on very small nanoparticles is consistent with deep penetration of SRP into cell DNA interiors, oxidative stress, and carcinogenesis.

In plain English

This exploratory laboratory study examined tremolite-actinolite fibers from the lungs of deceased workers from the Quebec chrysotile asbestos mines. Using electron microscopy, the authors examined nine fibers from three workers' lungs: eight tremolite-actinolite fibers and one tremolite-actinolite and anthophyllite composite. Four of the nine were analyzed in further depth, including with high-resolution transmission electron microscopy. All nine were coated with extremely small particles, which the authors named silica-rich particles. Chemical scans of the coating on one fiber detected only oxygen and silicon, apart from trace copper from the sample grid. On another fiber, 100 particles were measured. Their diameters ranged from 2.6 to 8.4 angstroms, and 38 percent fell between 4.0 and 4.9 angstroms. The authors read the images as showing the fibers' silicate chains breaking apart into these particles. They attributed this most likely to oxidation during the lung's attempts to engulf the fibers. They concluded that their preliminary data support the hypothesis that these particles cause mesothelioma linked to asbestiform tremolite-actinolite. They stated that their conclusions are not statistically proven and that the particles' toxicity has not yet been fully explored.

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: Exploratory electron microscopy study of mineral fibers recovered from human lung tissue
• Who was studied: Nine fibers from mineral residues in the lungs of three deceased workers from the Quebec chrysotile asbestos mines, examined at high TEM magnification; four of the nine (A1, B2, E2 and O) were analyzed further, including by HRTEM; dates not given
• Exposure: Tremolite-actinolite fibers in the lungs of workers from Quebec chrysotile mines: eight tremolite-actinolite fibers and one tremolite-actinolite and anthophyllite composite
• Main results:
  • All nine fibers were coated with silica-rich particles
  • Four of the nine fibers (A1, B2, E2 and O) were analyzed in further depth, including high-resolution TEM
  • Chemical scans of the coating on fiber A1 detected only oxygen and silicon, apart from trace copper from the copper grid
  • Of 100 particles measured on fiber B2, diameters peaked at 4.0 to 4.9 angstroms (38 percent). The minimum was 2.6 angstroms and the maximum 8.4 angstroms.
  • The authors described the silicate chains breaking up into dispersed particles. They attributed this to oxidation, most likely from attempted or 'frustrated' phagocytosis in the lungs.
  • The authors concluded that the particles are crystalline, not amorphous as their earlier study had described the coatings
  • In fiber O2, three lateral zones of silica-rich particles spanned the entire fiber length
• The authors' conclusion: The authors concluded that their preliminary data support the hypothesis that silica-rich particles are the agents of mesothelioma induction by asbestiform tremolite-actinolite, and that such particles may also develop on other asbestiform silicate minerals
• Limitations the authors state:
  • The study was exploratory, and its conclusions are preliminary and not statistically proven
  • The toxicity of the silica-rich particles has not yet been fully explored
  • Visualization was not good enough to measure particle sizes on fiber E2

Topics

The National Library of Medicine indexes this study under subjects our site covers: Actinolite, Tremolite.

Medical terms in this study, explained in our Lexicon: Tremolite, Actinolite, Amphibole Group, Tetrahedral Site, Phagocytosis, Oxidative Stress, Carcinogenesis.

Related studies

• The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part III. Radiographic findings — H.E. Amandus, R. Althouse, et al. (1987)
• The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part II. Mortality — H.E. Amandus, R. Wheeler (1987)
• The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part I. Exposure estimates — H.E. Amandus, R. Wheeler, et al. (1987)
• Analytical Transmission Electron Microscopy of Amphibole Fibers From the Lungs of Quebec Miners — M. Germine, J.H. Puffer (2015)
• Radiological survey of past and present vermiculite miners exposed to tremolite — J.C. McDonald, P. Sebastien, et al. (1986)
• Malignant mesothelioma caused by childhood exposure to long-fiber low aspect ratio tremolite — F. Magee, J.L. Wright, et al. (1986)

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