Lung cancer in a patient with predominantly short tremolite fibers in his lung

Our plain-English summary of Lung cancer in a patient with predominantly short tremolite fibers in his lung, by N. Kohyama, M. Fujiki, T. Kishimoto, et al (American Journal of Industrial Medicine, 2017).

The study

• Authors: N. Kohyama, M. Fujiki, T. Kishimoto, K. Morinaga
• Journal: American Journal of Industrial Medicine
• Published: 2017;60(9):831-838
• Type of article: Case report
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The carcinogenicity of short tremolite fibers in human has not been cleared and has been argued hitherto. A lung cancer patient had worked at a gabbro quarry. Particles isolated from the excised lung parenchyma of the patient were measured for asbestos bodies (ABs) and asbestos fibers (AFs). The concentrations of ABs were 3964 AB/g dry lung, and AFs were 5.60 × 106 fibers/g dry lung (>5 um in length) and 22.5 × 106 fibers/g dry lung (>1 um in length). AFs were mostly tremolite fibers and under 7 um in length (mean length 4.0 um, standard deviation 2.8 um). Almost all fibers were <10 um in length and an aspect ratio (AR) of <20:1 and ≥3:1. The patient had never smoked. His wife, who had worked with him in the quarry, had died of pleural mesothelioma. This study strongly indicates that such short tremolite fibers will induce lung cancer and possibly mesothelioma in human.

© 2017 Wiley Periodicals, Inc.

In plain English

This case report described one Japanese man with lung cancer. He had worked from 1970 to 1980 at a quarry in Ehime Prefecture that crushed hornblende gabbro rock. The quarry was not known to handle asbestos. He had never smoked, had no pleural plaques or lung fibrosis on imaging, and was diagnosed with stage IA adenocarcinoma in 2011. His wife, who did the same quarry work, died of pleural mesothelioma. His lung tissue held 3964 asbestos bodies per gram of dry lung, slightly below Japan's 5000 level for a twofold lung cancer risk. Fiber counts were 5.60 million per gram longer than 5 micrometers and 22.5 million longer than 1 micrometer, both above the twofold-risk levels. Almost all fibers were tremolite, and 74.6% of these were shorter than 5 micrometers. A rock sample from the quarry contained massive crystalline tremolite but no asbestiform tremolite fibers. Tremolite from old quarry filters matched the lung fibers in size. The wife's lung was not analyzed. The authors concluded that the case suggests short tremolite fibers can induce lung cancer and possibly mesothelioma.

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: case report (lung fiber burden analysis of one patient, with analysis of a quarry rock sample and old cotton filters)
• Who was studied: One 88-year-old man who never smoked, a former worker at a hornblende gabbro quarry in Seiyo city, Ehime Prefecture, Japan (1970 to 1980). He was diagnosed with stage IA adenocarcinoma of the left upper lobe in 2011. His wife worked at the same quarry over the same period and died of pleural mesothelioma in 2002 at age 75.
• Exposure: Short tremolite fibers, which the authors inferred to be cleavage fragments from crushed rock containing massive crystalline (non-asbestiform) tremolite. The rock also held a small amount of serpentine. The patient's job was removing mud by hand from filters of the quarry's waste slurry filtration system.
• Main results:
  • The patient's lung contained 3964 asbestos bodies per gram of dry lung, slightly lower than the 5000 per gram level judged as conferring a twofold risk of lung cancer.
  • Asbestos fiber concentrations in the patient's lung were 5.60 million fibers per gram of dry lung longer than 5 micrometers and 22.5 million fibers per gram longer than 1 micrometer. Both were above the twofold-risk thresholds of 2 million and 5 million.
  • Almost all lung fibers were tremolite: 100% of fibers longer than 5 micrometers and 99.2% of fibers longer than 1 micrometer. Two crocidolite fibers were found (2 of 238).
  • Of the 236 tremolite fibers measured in the lung, 74.6% were shorter than 5 micrometers and 97.0% were shorter than 10 micrometers. The geometric mean length was 3.26 micrometers.
  • 96.6% of the lung tremolite fibers had a length-to-width (aspect) ratio of less than 20:1.
  • In a rock sample collected from the quarry, polarized light microscopy showed massive crystalline forms of tremolite, and no asbestiform tremolite fibers were found.
  • Short tremolite fibers and chrysotile were found in old cotton filters from the quarry. The sizes and aspect ratios of the filter tremolite fibers did not differ from those of the lung tremolite fibers. No chrysotile was found in the patient's lungs.
  • The patient's lung cancer was attributed to occupational asbestos exposure, and he received workers' compensation.
• The authors' conclusion: The authors concluded that this case suggests exposure to short tremolite fibers can induce lung cancer and possibly mesothelioma in humans. (The abstract states this more strongly, as 'strongly indicates'.)
• Limitations the authors state:
  • No fiber burden analysis was done on the wife's lungs because not enough lung sample was available.
  • Phase contrast microscopy cannot recognize small asbestos bodies, which the authors give as the reason the asbestos body count was lower than the fiber counts.

Topics

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

Medical terms in this study, explained in our Lexicon: Lung Cancer, Tremolite, Parenchyma, Asbestos Bodies, Aspect Ratio (Length-to-diameter ratio), Pleural Mesothelioma, Mesothelioma.

Related studies

• Pulmonary fibrosis in workers exposed to non-asbestiform tremolite asbestos minerals — H.Y. Yang, R.H. Shie, et al. (2013)
• Comparison of Calidria chrysotile asbestos to pure tremolite: final results of the inhalation biopersistence and histopathology examination following short-term exposure — D.M. Bernstein, J. Chevalier, et al. (2005)
• Lung mineral fibers of former miners and millers from Thetford-Mines and asbestos regions: a comparative study of fiber concentration and dimension — A. Nayebzadeh, A. Dufresne, et al. (2001)
• Comparison of Calidria chrysotile asbestos to pure tremolite: inhalation biopersistence and histopathology following short-term exposure — D.M. Bernstein, J. Chevalier, et al. (2003)
• Tremolite-actinolite fiber coatings of sub-nanometer silica-rich particles in lungs from deceased Quebec miners — M. Germine, J.H. Puffer (2020)
• Rat model demonstrates a high risk of tremolite but a low risk of anthophyllite for mesothelial carcinogenesis — D. Aierken, Y. Okazaki, et al. (2014)

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