Detection of pleural plaques in workers exposed to inhalation of natural fluoro-edenite fibres

Our plain-English summary of Detection of pleural plaques in workers exposed to inhalation of natural fluoro-edenite fibres, by V. Rapisarda, C. Ledda, V. Ricceri, et al (Oncology Letters, 2015).

The study

• Authors: V. Rapisarda, C. Ledda, V. Ricceri, F. Arena, A. Musumeci, A. Marconi, L. Fago, M. Bracci, L. Santarelli, M. Ferrante
• Journal: Oncology Letters
• Published: 2015;9(5):2046-2052
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Fluoro-edenite is a natural mineral species initially isolated in Biancavilla, Sicily. The fibres are similar in size and morphology to certain amphibolic asbestos fibres, the inhalation of which may cause chronic inflammation and cancer. Occupational asbestos exposure is known to be associated with pleural and lung diseases, including pleural plaques. The aim of this study was to report the pleural and lung parenchymal lesions detected by high-resolution computed tomography (HRCT) in a group of construction workers exposed to fluoro-edenite. Information regarding life habits and occupational history was collected from 43 workers enrolled into the study. The participants underwent physical examination, blood analysis, search for uncoated fibres and ferruginous bodies in the sputum, pulmonary function tests, including diffusion capacity for carbon monoxide (TLCO), and HRCT chest imaging. A general descriptive outcome analysis was also conducted; a prevalence ratio (PR) with 95% confidence interval and a two-tailed test P-value were calculated for pleural plaques using log-binomial regression, measuring plaque size and thickness, and cumulative exposure index (CEI). The mean values of the functional respiratory tests were within the normal range for all participants. A restrictive ventilatory defect was identified in two (5%) subjects and an obstructive ventilatory defect in three (7%) subjects. TLCO was reduced in two additional participants. Fibres were detected in 19 (44%) of subjects. Pleural involvement was documented in 39 (91%) workers, of whom 31 (72%) had bilateral plaques. Calcifications were detected in 25 (58%) of these participants. PR indicated a progressive increase in the risk of developing pleural lesions with rising CEI, i.e. length of exposure. The present findings demonstrate for the first time the presence of pleural plaques in the lungs of subjects exposed to fluoro-edenite fibres, and not to asbestos, through residing in Biancavilla and through their occupation.

In plain English

This study examined male construction workers who lived and worked in Biancavilla, Sicily. A local quarry there supplied gravel and sand containing fluoro-edenite, a natural fibre the authors describe as similar to some amphibole asbestos fibres. Of 52 workers invited between 2009 and 2013, nine were excluded, five because of previous asbestos exposure, leaving 43. Exposure was scored from job histories as a cumulative exposure index, since no airborne fibre measurements were available. Workers had breathing tests, sputum tests and high-resolution CT chest scans. Pleural plaques were found in 39 of the 43 workers, 31 of them on both sides, and calcification in 25. Fluoro-edenite fibres were found in the sputum of 19 workers. Average lung function was within the normal range, and seven workers had low-grade lung fibrosis. Compared with the lowest exposure-index group (1-9), the plaque prevalence ratio was 1.45 (95% confidence interval 1.12 to 1.78) at index 10-19, rising to 3.32 (3.24 to 3.48) at 40 or more. The authors concluded this was the first report of pleural plaques in people exposed to fluoro-edenite rather than asbestos. They called the study preliminary.

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: Preliminary study of a group of workers, each examined once with questionnaire, blood and sputum tests, lung function tests and HRCT chest scans. Plaque prevalence ratios were compared across exposure-index groups using log-binomial regression.
• Who was studied: 52 male construction workers living and working in the Biancavilla area (Sicily, Italy) were invited between 2009 and 2013. 9 were excluded (previous asbestos exposure n=5, bronchopneumonia n=2, tuberculosis n=1, allergic bronchial asthma n=1), leaving 43 participants with a mean age of 49.3 years. All had lived in Biancavilla for more than 40 years.
• Exposure: Fluoro-edenite fibres from lava gravel and sand from the local Mount Calvario quarry, used in pavements, plaster and cement. 38 of 43 workers (88%) had personally handled and mixed quarry gravel until 1998, and all had restored houses built with quarry material. Exposure was estimated from occupational history as a cumulative exposure index, with job weights from 0.01 (electricians) to 10 (carpenters, plasterers, plumbers). It was expressed in exposure units x years, not fibres/ml x years, because airborne fibre data were lacking.
• Main results:
  • Pleural involvement on HRCT was found in 39 of the 43 workers (91%). 31 workers (72%) had bilateral plaques.
  • Plaque calcification was found in 25 participants, reported as 58%.
  • Prevalence ratios for pleural plaques, compared with the lowest exposure-index group (1-9, set at 1.00), were: 1.45 (CI 1.12-1.78, P printed as >0.05) for index 10-19; 1.98 (1.84-2.12) for 20-29; 2.36 (2.01-2.58) for 30-39; and 3.32 (3.24-3.48) for 40 or more. P-values for the last three groups are printed as >0.001. The authors described this as a progressive increase in risk of pleural lesions with rising exposure index.
  • Mean lung function values (% predicted) were within the normal range for all participants. 2 workers (5%) had a restrictive defect and 3 (7%) an obstructive defect. Gas transfer (TLCO) was reduced in 2 additional participants.
  • A slight reduction in lung function values with rising exposure index was not statistically significant.
  • Fluoro-edenite fibres (10-35 micrometres long, under 0.5 micrometres in diameter) were recovered from the sputum of 19 of the 43 workers (44%). Ferruginous bodies were not found in any sample.
  • In the lung tissue, HRCT showed low-grade fibrosis in 7 workers (2 on one side, 5 on both sides) and rounded atelectasis on one side in 2 workers.
• The authors' conclusion: The authors concluded that their findings show, for the first time, pleural plaques in people exposed not to asbestos but to fluoro-edenite fibres through living and working in Biancavilla. They also said the lesions had a limited effect on respiratory function.
• Limitations the authors state:
  • No airborne fibre measurements or detailed exposure-frequency data were available, so exposure was expressed as a weighted job-based index rather than fibres/ml x years.
  • The authors describe the study as preliminary and say the resident population and larger cohorts of exposed workers need to be investigated.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Plaques, fluoro-edenite, Biancavilla, Chronic Inflammation, Asbestos Exposure, High-Resolution CT (HRCT), Habit, Occupational History.

Related studies

• Fluoro-edenite and carbon nanotubes: The health impact of 'asbestos-like' fibres — E. Miozzi, V. Rapisarda, et al. (2016)
• Monitoring of fluoro-edenite fibre pollution through the study of sheep lymph nodes as a model of a biological indicator — V. Rapisarda, G. Rapisarda, et al. (2005)
• Early effects of fluoro-edenite: correlation between IL-18 serum levels and pleural and parenchymal abnormalities — C. Ledda, C. Loreto, et al. (2016)
• Occupational exposure to fluoro-edenite and prevalence of anti-nuclear autoantibodies — V. Rapisarda, C. Loreto, et al. (2018)
• Carcinogenicity of fluoro-edenite, silicon carbide fibres and whiskers, and carbon nanotubes — Y. Grosse, D. Loomis, et al. (2014)
• Mineral fibre toxicity: expression of retinoblastoma (Rb) and phospho-retinoblastoma (pRb) protein in alveolar epithelial and mesothelial cell lines exposed to fluoro-edenite fibres — G. Musumeci, V. Cardile, et al. (2011)

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