Chest imaging and lung function impairment after long-term occupational exposure to low concentrations of chrysotile

Our plain-English summary of Chest imaging and lung function impairment after long-term occupational exposure to low concentrations of chrysotile, by D. Spyratos, D. Chloros, B. Haidich, et al (Archives of Environmental & Occupational Health, 2012).

The study

• Authors: D. Spyratos, D. Chloros, B. Haidich, L. Dagdilelis, S. Markou, L. Sichletidis
• Journal: Archives of Environmental & Occupational Health
• Published: 2012;67(2):84-90
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The aim of the present study was the investigation of radiographic findings in relation to lung function after occupational exposure to permissible levels of relatively pure chrysotile (0.5-3% amphiboles). We studied 266 out of the total 317 employees who have worked in an asbestos cement factory during the period 1968-2004 with chest x-ray, high-resolution computed tomography (HRCT) and lung function tests. Sensitivity of chest x-ray was 43% compared to HRCT. Abnormal HRCT findings were found in 75 subjects (67%) and were related to age, occupational exposure duration, and spirometric data. The presence of parenchymal or visceral pleural lesions (exclusively or as the predominant abnormality) was being accompanied by lower total lung capacity and diffusion capacity. HRCT was much more sensitive than chest x-ray for occupational chrysotile exposure. Lung function impairment was related with parenchymal but not with pleural HRCT abnormalities.

In plain English

The authors studied workers from an asbestos cement factory that used chrysotile from 1968 until 31 December 2004. The researchers were based in Thessaloniki, Greece. The chrysotile contained on average 0.5% amphiboles (rarely 3%). Of 317 employees who had worked there at least 5 years, the 266 still alive had chest x-rays and breathing tests in 2003 and 2004. Of these, 112 also accepted high-resolution CT (HRCT) and further lung tests. Measured airborne fiber levels fell from 6.49 to 1.7 fibers/cm3 over 1968 to 1983 and stayed below 1 fiber/cm3 from 1984. Chest x-rays showed pleural findings in 55 of the 266 workers. HRCT showed abnormalities in 75 of the 112 scanned workers, and chest x-ray had picked up 43% (32/75) of these. After adjustment for smoking, age and exposure duration, workers with lung-tissue (parenchymal) or visceral pleural changes had lower total lung capacity and diffusion capacity than workers with normal HRCT. Workers with pleural plaques did not differ significantly. The authors concluded that HRCT was much more sensitive than chest x-ray. They named as the main limitation that more than half of participants declined HRCT.

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: Study of a cohort of asbestos cement workers examined in 2003 to 2004 with chest x-ray and spirometry; a subgroup also had HRCT, lung volumes and diffusion capacity
• Who was studied: 317 employees had worked at least 5 years in the asbestos cement plant between 1968 and 2004. All 266 still alive (current and retired) were examined from 1 January 2003 to 31 December 2004. 112 of them (mean age 56.6 years) also had HRCT and further lung function tests.
• Exposure: Chrysotile from Canada and Russia, later from Zidani (Kozani, Greece), with average amphibole contamination of 0.5% (rarely 3%). Products contained about 8% to 9% chrysotile. Departments were grouped I to III by increasing fiber exposure. The authors state airborne levels were always within permissible limits.
• Main results:
  • Measured airborne fiber concentration fell from 6.49 to 1.7 fibers/cm3 during 1968 to 1983. From 1984 it was always below 1 fiber/cm3, with mean values falling from 0.8 to 0.07.
  • On chest x-ray, pleural findings were seen in 55 of 266 workers and parenchymal small opacities in 1. X-ray lesions were significantly associated with age, exposure period and time since first exposure.
  • Smoking habit was associated with x-ray lesions (p = .048). 82% (45/55) of workers with x-ray lesions were current or ex-smokers, compared with 54% of workers without abnormalities.
  • HRCT abnormalities were found in 67% (75/112) of scanned workers. HRCT groups were: A (normal) 37; B (honeycombing and/or septal thickening) 20; C (diffuse pleural thickening, parenchymal bands and/or rounded atelectasis) 26; D (pleural plaques) 29.
  • Compared with HRCT, chest x-ray sensitivity was 43% (32/75) and specificity was 100%. 43 workers with normal chest x-rays had abnormalities on HRCT.
  • After adjustment for smoking, age and exposure duration, total lung capacity and diffusion capacity were lower in groups B and C than in group A. For group B vs A, the TLC mean difference was -11.08 %pred (95% CI -18.57 to -3.60, p 0.004) and the DLCO difference was -13.08 (95% CI -24.54 to -1.62, p .026). For group C vs A, the TLC difference was -7.70 (95% CI -15.25 to -0.16, p 0.045) and the DLCO difference was -12.31 (95% CI -23.72 to -0.90, p .035).
  • Workers with pleural plaques only (group D) did not differ significantly from workers with normal HRCT (group A) on any lung function measure in the adjusted analysis.
  • Lung function impairment was defined as below 80% of predicted. An abnormal chest x-ray was a better predictor of impairment than HRCT groups. For example, the odds ratio for FVC impairment was 7.8 (95% CI 2.7 to 22.4, p less than .001) for an abnormal x-ray, compared with 3.8 (95% CI 1.2 to 11.5) for HRCT group B.
• The authors' conclusion: The authors concluded that HRCT was much more sensitive than chest x-rays as a screening method for workers exposed to chrysotile within permissible levels. After adjustment for age, smoking and years of exposure, they found that lower TLC and DLCO were related to parenchymal and visceral pleural abnormalities, but not to parietal pleural abnormalities, on HRCT.
• Limitations the authors state:
  • The authors state the main limitation was that more than 50% of participants refused HRCT (112 of 266 had it).

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Chrysotile, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Chrysotile, Amphibole Group, Asbestos-Cement, Chest X-Ray, High-Resolution CT (HRCT), Total Lung Capacity (TLC).

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