Progression of small, irregular opacities in chest radiographs of former asbestos workers

Our plain-English summary of Progression of small, irregular opacities in chest radiographs of former asbestos workers, by B. Świątkowska, W. Sobala, Z. Szubert (International Journal of Occupational Medicine and Environmental Health, 2012).

The study

• Authors: B. Świątkowska, W. Sobala, Z. Szubert
• Journal: International Journal of Occupational Medicine and Environmental Health
• Published: 2012;25(4):481-91
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: Pulmonary parenchymal changes appear many years after the start of exposure to asbestos and their progression has been observed to continue many years after cessation of the exposure. The aim of the present analysis is to assess the risk of progression of radiological changes in the respiratory system, based on long-term follow-up of groups of workers occupationally exposed to asbestos dust.

Materials And Methods: The analysis included 3144 individuals voluntarily applying for a medical examination in 2000-2010, who had performed at least two radiographs of the chest. Probability of progression in subsequent studies was based on the evaluation of radiographs for the presence of small, irregular type s, t, u opacities in the parenchymal lung tissue with profusion categories as specified in the classification of ILO, 1980. Multistate hidden Markov model was used in the statistical analysis.

Results: In the group of patients, small irregular opacities with a profusion of 1/1 or higher occurred in 640 (20%) patients in the first examination, and in 918 (29%) patients in the last examination. No parenchymal changes were observed in 1360 (43%) patients in the first examination (opacity profusion category 0/0), and in 645 (20%) patients in the last examination. The risk of progression of radiographic changes in former workers of asbestos processing plants is higher in smokers, from profusion category 0 to 1 - by 30% (HR = 1.30, 95% CI: 1.15-1.47), from profusion category 1 to 2 - by 50% (HR = 1.50, 95% CI: 0.92-2.45). The risk of progression of parenchymal changes decreases in the workers employed in subsequent calendar years: for category changes from 1 to 2, the decrease is nearly 40% for every 10 years of subsequent employment (HR = 0.60, 95% CI: 0.45-0.80). The probability of the progression increases with longer latency period: for change of category from 1 to 2, the increase is about 20% (HR = 1.19, 95% CI: 1.00-1.42) per 10 years of employment for blue collar workers. The risk of the 1 to 2 category progression is significant, nearly 2.5-fold higher in the workers employed in the asbestos-processing textile industry.

Conclusions: Our results show that the risk of progression of pulmonary parenchymal fibrotic processes was higher in the smokers, workers employed during the earlier calendar years of the discussed period, those with longer latency period, blue collar workers involved directly in the production processes, and employees of the asbestos cement and/or textile industries.

In plain English

This study followed 3144 former workers of Polish asbestos processing plants. They volunteered for Amiantus Programme check-ups in 2000–2010 and had at least two chest X-rays. X-rays were read for small, irregular opacities, which the authors link to lung scarring, on the 12-step 1980 ILO scale, then grouped into three categories (0, 1, 2). A statistical model allowed for reading errors. At the first X-ray 1360 people (43.2%) had none; at the last, 645 (20.5%). Opacities of 1/1 or more rose from 640 people (20.3%) to 918 (29.2%). In the final model, ever-smokers had higher risk of moving from category 0 to 1 (hazard ratio 1.30, 95% CI 1.15–1.47). For 1 to 2 the ratio was 1.50, but its interval (0.92–2.45) included 1. Moving from 1 to 2 was more likely in textile than asbestos-cement workers (HR 2.44, 95% CI 1.47–4.04). It was less likely for those starting work later (HR 0.60 per 10 years, 95% CI 0.45–0.80). Length of employment showed no significant influence. The authors noted participants chose to attend and lacked X-rays from their start of work.

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: Longitudinal follow-up (described by the authors as prospective) of repeated chest X-rays in former asbestos workers, analysed with multi-state hidden Markov models
• Who was studied: 3144 former workers (36.6% women) of 28 former asbestos processing plants in Poland. They volunteered for examinations under the Amiantus Programme in 2000–2010 and had at least two chest radiographs. They made up 46% of all programme participants.
• Exposure: Employment in asbestos processing plants until the 1997 Polish asbestos ban. The plants were asbestos-cement (55.3%), textile (13.6%), sealing products (9.4%), waterproofing products (9.4%), friction products (8.4%) and other plants. The article does not name fiber types. The factors analysed were duration of employment, calendar period of starting work, latency, production versus non-production job, sex and smoking.
• Main results:
  • Whole group of 3144: 1360 (43.2%) had no small irregular opacities (category 0/0) at the first examination, compared with 645 (20.5%) at the last examination.
  • Whole group: opacities of profusion 1/1 or higher were seen in 640 (20.3%) at the first examination and in 918 (29.2%) at the last.
  • Final multivariate model, ever-smokers versus others, progression from category 0 to 1: hazard ratio 1.30 (95% CI 1.15–1.47).
  • Final multivariate model, ever-smokers versus others, progression from category 1 to 2: hazard ratio 1.50 (95% CI 0.92–2.45). The interval includes 1.
  • Final multivariate model, progression from category 1 to 2: hazard ratio 0.60 (95% CI 0.45–0.80) per 10 years later start of work.
  • Final multivariate model, progression from category 1 to 2, textile industry workers versus asbestos-cement workers: hazard ratio 2.44 (95% CI 1.47–4.04).
  • Final multivariate model, workers in direct production jobs, progression from category 1 to 2: hazard ratio 1.19 (95% CI 1.00–1.42). Table 5 defines this as per 10 years of time since start of employment.
  • The analysis showed no significant influence of duration of asbestos-exposed employment on the risk of progression.
  • Single-factor analysis, women compared with men: lower risk of progression from category 0 to 1 (HR 0.80, 95% CI 0.71–0.90).
• The authors' conclusion: The authors concluded that the risk of progression of lung fibrotic changes was higher in five groups: smokers, people employed in earlier calendar years, those with longer latency, blue collar production workers, and employees of the asbestos-cement and/or textile industries.
• Limitations the authors state:
  • Participants decided for themselves to attend the first and later examinations. Selection may therefore reflect a wish to know a diagnosis, or more severe respiratory symptoms.
  • Workers had no baseline chest X-rays from the start of their work to compare against.
  • The findings concern ILO X-ray categories, which are not the same as the presence of interstitial changes.
  • The results relate to asbestos processing workers with relatively well documented exposure. They do not cover other settings such as repair plants, shipyards or construction work.

Topics

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

Medical terms in this study, explained in our Lexicon: Chest X-Ray, Latency, Asbestos-Cement.

Related studies

• Is lung cancer associated with asbestos exposure when there are no small opacities on the chest radiograph? — P. Wilkinson, D.M. Hansell, et al. (1995)
• Progression of irregular opacities in asbestos miners — G.K. Sluis-Cremer, E. Hnizdo (1989)
• Risk and significance of chest radiograph and pulmonary function abnormalities in an elderly cohort of former nuclear weapons workers — M.A. Mikulski, P.G. Hartley, et al. (2011)
• Cigarette smoke, asbestos, and small irregular opacities — W. Weiss (1984)
• Cigarette smoking and small irregular opacities — W. Weiss (1991)
• Factors influencing the reading of small irregular opacities in a radiological survey of asbestos miners in South Africa — G.K. Sluis-Cremer, P.A. Hessel, et al. (1989)

Browse more research in International Journal of Occupational Medicine and Environmental Health, or return to medical research.