High frequency and severity of pleural changes in former workers exposed to anthophyllite associated with other contaminating amphibole asbestos in Brazil

Our plain-English summary of High frequency and severity of pleural changes in former workers exposed to anthophyllite associated with other contaminating amphibole asbestos in Brazil, by R.F. Macedo, E.M.F.P. Cerqueira, E. Algranti, et al (American Journal of Industrial Medicine, 2019).

The study

• Authors: R.F. Macedo, E.M.F.P. Cerqueira, E. Algranti, D. Silva, E.M. De Capitani
• Journal: American Journal of Industrial Medicine
• Published: 2019;62(6):503-510
• Read it: PubMed · Publisher

Abstract

Objective: To evaluate the frequency and severity of pleuropulmonary alterations in anthophyllite-exposed former workers in Itapira, São Paulo, Brazil. The amphibole anthophyllite, a magnesium-iron silicate, had its mining, marketing, and use forbidden in Brazil in 1995.

Methods: Former workers were followed from 1999 to 2011. All completed chest X-ray interpreted using the International Labour Office (ILO) classification. High-resolution computed tomography was used at the final evaluation. Spirometry assessed forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and FEV1/FVC throughout the follow-up period. Samples from the mined ore were analyzed by X-ray diffraction (XRD) and scanning electron microscopy coupled to energy dispersive spectroscopy (SEM-EDS).

Results: XRD and SEM-EDS confirmed the presence in ore of anthophyllite at a concentration of 75%, in addition to tremolite and other amphiboles in lower concentrations. Twenty-eight subjects were evaluated. Median time of exposure was 3 years (minimum = 1; maximum = 18; interquartile interval = 1-4). Twenty cases of pleural abnormalities were diagnosed in 26 evaluated (77%). The average latency time was 25.6 ± 7.4 years. Two individuals (7.7%) showed progressive worsening of diffuse pleural thickening (DPT) and exhibited an annual FVC decrease of 85 mL and 150 mL, respectively.

Conclusion: This small sample showed a very high index of nonmalignant pleural abnormalities in anthophyllite-exposed workers compared with workers exposed to other kinds of fibers. Rapidly progressive DPT, defined by the severity of pleural compromise, was possibly secondary to the presence of other amphibole types in the inhaled dust. No significant loss of FVC was found in the studied group as a whole. No cases of asbestosis, lung carcinoma, and mesothelioma were diagnosed in this cohort.

© 2019 Wiley Periodicals, Inc.

In plain English

This prospective cohort study followed former workers of an anthophyllite asbestos mine in Itapira, Brazil. Of around 50 former employees, 30 were traced. The final group of 28 men had chest X-rays and spirometry in 1999, 2003, 2007 and 2011, though attendance varied and only five had spirometry in 2003. All 26 men seen in 2011 had high-resolution CT. Median time at the mine was 3 years. Ore samples were 75% anthophyllite, with less chlorite, actinolite and other amphiboles. Small amounts of tremolite and winchite were seen but needed confirmation. In 2011, CT found asbestos-related pleural changes in 20 of 26 men (77%); X-ray found 9. Two men developed rapidly progressive diffuse pleural thickening, losing 85 and 150 mL of FVC per year. Mesothelioma was ruled out in both. No asbestosis, lung cancer or mesothelioma was found in this cohort so far; the authors said the small group allowed no inference about cancer risk. Group FVC did not change significantly. The authors concluded that pleural changes were very frequent and the severe cases possibly indicated involvement of tremolite and other amphiboles.

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: Observational prospective cohort study. It began with a cross-sectional evaluation in 1999, followed by re-evaluations every 4 years (2003, 2007, 2011), and included mineralogical analysis of ore samples.
• Who was studied: Former workers of an anthophyllite mine in Itapira, São Paulo, Brazil. Of an original cohort of around 50 employees, 30 were traced and contacted, and the final group was 28 men (mean age 44.1 at intake; 78.5% smokers or ex-smokers). They were followed from 1999 to 2011. Numbers examined varied by year: chest X-ray n = 28, 22, 26 and 26, and 26 were evaluated in 2011.
• Exposure: Work in the mine's production chain: manual extraction, ore selection, truck loading, grinding, sorting, bagging and shipping. The ore was 75% anthophyllite with lower concentrations of chlorite, actinolite and other amphiboles. Small amounts of tremolite and winchite were detected by XRD, with confirmation still needed. Mean exposure time was 3.6 plus or minus 3.8 years, and the median was 3 years (range 1 to 18). Air sampling was not possible.
• Main results:
  • At the 2011 evaluation, high-resolution CT found asbestos-related pleural changes in 20 of 26 subjects (77%). Chest X-ray at the same evaluation detected only 9 cases (34.6%).
  • Latency from the start of exposure to detection of pleural changes averaged 25.6 plus or minus 7.4 years (median 26.5 years).
  • Mean exposure time did not differ significantly between workers with pleural changes (3.75 years) and those without (2.17 years), P = 0.36.
  • Two patients (7.7%) developed late, rapidly progressive diffuse pleural thickening with pleurisy. Their FVC fell by 85 mL/year and 150 mL/year respectively.
  • Mesothelioma was suspected in these two cases but ruled out in both. A pleural biopsy in one showed pleural fibrosis.
  • So far, no pleural mesothelioma, lung cancer, or changes compatible with asbestosis were observed in the cohort. One former worker who did not take part in the study had been diagnosed and treated for lung carcinoma before the cohort was set up. The authors stated that the small group does not allow epidemiological inference about excess cancer risk.
  • In all subjects, mean FVC was 4.1 L in 1999 and 3.9 L in 2011. The difference was not significant (P = 0.65).
  • In all subjects, mean FEV1 fell from 3.5 L in 1999 to 2.9 L in 2011, a statistically significant decline (P = 0.01). The authors considered this probably related to the high rate of smokers and former smokers.
• The authors' conclusion: The authors concluded that the prevalence of nonmalignant pleural changes was very high compared with studies of workers exposed to other fiber types, though similar to an anthophyllite-exposed cohort in Japan. They also concluded that the severe, rapidly progressive cases possibly indicate involvement of tremolite and other amphiboles.
• Limitations the authors state:
  • High-resolution CT was not performed in all individuals in the first three evaluations. The sharp rise in diagnoses in 2011 reflects the use of CT, which creates possible bias in the latency estimate.
  • Spirometry could not be performed in all patients in 2003.
  • Not all individuals completed all four evaluations. Because the mine owner located and referred the former employees, there may have been selection bias.
  • The small group size does not allow epidemiological inference about excess cancer risk. It may also explain why lung function did not decrease significantly.
  • Airborne dust could not be sampled because the mine was inactive; only ore samples were analyzed.
  • The presence of tremolite and winchite in the ore needs confirmation by further analysis.

Topics

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

Medical terms in this study, explained in our Lexicon: Anthophyllite, Amphibole Asbestos, Amphibole Group, Silicate, Chest X-Ray, Spirometry, FEV1, FEV1/FVC Ratio.

Related studies

• Rat model demonstrates a high risk of tremolite but a low risk of anthophyllite for mesothelial carcinogenesis — D. Aierken, Y. Okazaki, et al. (2014)
• Causes of death in former asbestos-cement workers in the state of São Paulo, Brazil — G.A. Fernandes, E. Algranti, et al. (2021)
• Incidence of cancer among anthophyllite asbestos miners in Finland — L.O. Meurman, E. Pukkala, et al. (1994)
• Workers with Libby amphibole exposure: retrospective identification and progression of radiographic changes — T.C. Larson, C.A. Meyer, et al. (2010)
• Four cases of mesothelioma among Finnish anthophyllite miners — A. Karjalainen, L.O. Meurman, et al. (1994)
• Non-malignant consequences of decreasing asbestos exposure in the Brazil chrysotile mines and mills — E. Bagatin, J.A. Neder, et al. (2005)

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