Non-malignant asbestos-related diseases in Brazilian asbestos-cement workers

Our plain-English summary of Non-malignant asbestos-related diseases in Brazilian asbestos-cement workers, by E. Algranti, E.M. Mendonça, E.M. DeCapitani, et al (American Journal of Industrial Medicine, 2001).

The study

• Authors: E. Algranti, E.M. Mendonça, E.M. DeCapitani, J.B. Freitas, H.C. Silva, M.A. Bussacos
• Journal: American Journal of Industrial Medicine
• Published: 2001;40(3):240-54
• Cited by: 42 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Production of asbestos-cement products in Brazil started in the 1940s, peaked in the 60-70s and is still an active industry. This study was designed to assess the non-malignant effects of asbestos exposure in the asbestos-cement industry in Brazil.

Methods: A group of 828 former asbestos-cement workers enrolled in a cross-sectional and cohort study of respiratory morbidity, submitted to a detailed occupational history, respiratory symptoms questionnaire, spirometry, PA chest x-ray, and high resolution computed chest tomography (HRCT). Asbestos exposure was assessed by years of exposure, cumulative exposure (a semi-quantitative method), and latency time from first exposure. Asbestosis and pleural thickening were assessed according to HRCT criteria.

Results: Asbestosis was present in 74 (8.9%) and pleural thickening in 246 (29.7%). Using the HRCT as the "best available evidence", it was shown that were more false negatives than false positives in the x-ray readings for parenchymal (21.6% false negatives, 4.2% false positives) and pleural (26.0% false negatives, 14.4% false positives) diseases due to asbestos. Latency time from first exposure was the best predictor for both asbestosis and pleural thickening. Subjects in the higher exposure groups presented lower levels of lung function. Obstructive defects were significantly related to smoking, shortness of breath, body mass index, and age, whereas restrictive defects were related to asbestosis, shortness of breath, and latency time. Chronic bronchitis increased with latency time in the three smoking groups and was significantly related to pleural thickening (OR 1.56 (1.00-2.42)). Shortness of breath was significantly associated with body mass index and pleural thickening (OR 1.30 (1.24-2.09)).

Conclusions: Pleural thickening and asbestosis showed a significant association with latency time and exposure. FVC and FEV(1) decreased across increasing profusion with an added effect of pleural thickening. There was a significant and independent effect of exposure on lower levels of FVC and FEV(1). Obstructive defects were mainly related to smoking and restriction to asbestosis. Dust exposure and smoking were synergistic in increasing chronic bronchitis and shortness of breath report. Shortness of breath report was also related to pleural thickening and higher body mass index.

Copyright 2001 Wiley-Liss, Inc.

In plain English

This study examined 828 men formerly employed at a large Brazilian asbestos-cement plant that operated from 1941 to 1992. They were invited through a former workers' association and enrolled between 1995 and 1999. The authors said the group could not be considered a sample in the strict sense. Chrysotile was used throughout, and crocidolite in pipe production until 1979. Each man completed a symptom questionnaire, spirometry, a chest x-ray and a high resolution CT scan. On CT, asbestosis was found in 74 men (8.9%) and pleural thickening in 246 (29.7%). Chest x-rays missed 21.6% of the CT-defined asbestosis cases and 26.0% of the CT-defined pleural thickening cases. Time since first exposure predicted both conditions better than years of exposure or cumulative exposure. The authors reported a significant, independent effect of exposure on lower lung function (FVC and FEV1). Restrictive defects were associated with asbestosis (odds ratio 5.21, confidence interval 2.50 to 10.98), while obstructive defects were mainly related to smoking. The authors concluded that dust exposure and smoking were synergistic in increasing reports of chronic bronchitis and shortness of breath.

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: Cross-sectional evaluation (first examination) of former workers enrolled in a study planned to include longitudinal follow-up
• Who was studied: Former workers of one large asbestos-cement plant in Brazil that operated from 1941 through 1992. 868 workers were enrolled between June 1995 and August 1999. After exclusions, 828 men were retained for analysis; those excluded included 24 men without a CT scan and four women in administrative jobs. An estimated 11,000 people worked at the plant during its operation.
• Exposure: Asbestos-cement manufacturing of sheets, pipes, water reservoirs and moulded roofing items. Chrysotile was the main fiber throughout and the only fiber after 1979. Crocidolite was used in small amounts in pipe production until 1979, and the production areas were not completely separated. Exposure was estimated three ways: years of exposure, latency since first exposure, and a semi-quantitative cumulative index. The index was built from a 1 to 10 job dustiness scale devised by long-tenure workers and an inspector.
• Main results:
  • On high resolution CT, asbestosis was present in 74 of the 828 men (8.9%) and pleural thickening in 246 (29.7%). A further 166 men (20%) had CT lung changes classed as suspect.
  • The authors used CT as the best available evidence. Against it, chest x-rays missed 21.6% of the CT-defined asbestosis cases (16 of 74 by Table IV) and 26.0% of the CT-defined pleural thickening cases (64 of 246 by Table V). The corresponding false-positive figures were 4.2% for lung changes and 14.4% for pleural changes.
  • Men with asbestosis had a mean of 19.9 (SD 8.9) years of exposure, compared with 11.7 (SD 8.5) years in men without asbestosis.
  • For both asbestosis and pleural thickening, the effect of latency (time since first exposure) was greater than that of years of exposure or cumulative exposure. This was especially so for pleural thickening.
  • Of the 74 men with asbestosis, 66 (89.2%) also had pleural thickening.
  • Spirometry was normal in 585 men (70.7%). An obstructive defect was found in 153 (18.5%), a restrictive defect in 66 (8%) and a combined defect in 24 (2.9%).
  • In life table analysis, exposure was significantly related to lower FVC and FEV1 for all three exposure indices. The latency effect on FVC and FEV1 persisted after accounting for smoking, age and body mass index.
  • Restrictive defects were strongly associated with asbestosis (OR 5.21, CI 2.50 to 10.98).
  • Smoking, measured in pack-years, was mainly related to obstructive defects.
  • Chronic bronchitis symptoms were reported by 139 men (16.8%) and shortness of breath by 97 (11.8%). In regression models, pleural thickening was associated with chronic bronchitis (OR 1.56, CI 1.00 to 2.42). It was also associated with shortness of breath (OR 1.30, CI 1.24 to 2.09, as printed).
• The authors' conclusion: The authors concluded that pleural thickening and asbestosis were significantly associated with latency time and exposure. They found a significant and independent effect of exposure on lower FVC and FEV1. Obstructive defects were mainly related to smoking, and restrictive defects to asbestosis. Dust exposure and smoking were synergistic in increasing reports of chronic bronchitis and shortness of breath.
• Limitations the authors state:
  • The industry did not provide worker registers, so the participants cannot be considered a sample in the strict sense.
  • Selection bias may have occurred, because older, longer-exposed workers with more illness may have come forward, especially in the first study year.
  • The cumulative exposure index assumed a linear dustiness scale, which may have been wrong. There were no routine fiber measurements before 1980.
  • Changes in production methods and plant conditions over time could not be accounted for, because objective data were lacking.
  • Spirometry alone is fairly insensitive for detecting obstruction in the small airways.
  • Pleural plaques and diffuse pleural thickening were not distinguished on CT.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Asbestos Exposure, Cohort Study, Occupational History, Spirometry, Posteroanterior (PA) View, High-Resolution CT (HRCT), Cumulative Exposure.

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