Continued spirometry changes after cessation of exposure in asbestos-cement workers

Our plain-English summary of Continued spirometry changes after cessation of exposure in asbestos-cement workers, by B. Swiątkowska, W. Sobala, Z. Szubert, et al (Journal of Occupational and Environmental Medicine, 2014).

The study

• Authors: B. Swiątkowska, W. Sobala, Z. Szubert, N. Szeszenia-Dąbrowska
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2014;56(4):403-8
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: To assess further progression of spirometry parameters among former asbestos-cement plant workers.

Methods: The following parameters were assessed: forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and the ratio (FEV1/FVC) using a linear regression model with mixed effects.

Results: The analysis included 3005 individuals. Spirometrically defined restrictive ventilatory defects were registered in 21.6% of the patients, obstructive defects in 8.3%, whereas mixed changes in 7%. Current smokers had significantly lower levels of FEV1, FVC, and FEV1/FVC and a steeper decline compared with nonsmokers. More rapid progression was also observed along with increasing termination of exposure. Having higher exposure was associated with a slower decline in FEV1 and FEV1/FVC ratios.

Conclusions: This report indicates that asbestos-cement workers with higher cumulative exposure still had lower mean levels of spirometric parameters, despite cessation of asbestos exposure many years ago.

In plain English

This study analyzed breathing tests (spirometry) of 3005 former workers, 864 of them women, from eight asbestos-cement plants in Poland. They were examined between 2000 and 2012 in a national medical program for former asbestos workers. The plants used chrysotile, occasionally with small amounts of crocidolite. The authors estimated each worker's cumulative exposure to asbestos-containing dust and analyzed repeated test results statistically. On average, 16.5 years had passed since exposure ended. Restrictive breathing patterns were found in 21.6% of workers, obstructive patterns in 8.3% and mixed patterns in 7%. The most-exposed group (over 60 mg/m3·yr) had lower average test values than the least-exposed group (under 21 mg/m3·yr), but their values did not fall faster over time. Their FEV1/FVC ratio actually fell more slowly. Workers smoking 11 to 50 cigarettes a day declined faster than nonsmokers. The FEV1/FVC ratio fell faster the longer it had been since exposure ended. The authors concluded that more-exposed workers still had lower test values many years after exposure stopped. They noted that participants came forward voluntarily, which may have biased the group.

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 study of repeated spirometry results in former workers, analyzed with a linear regression model with mixed effects
• Who was studied: 3005 former workers (864 women) of eight asbestos-cement plants in Poland, examined from 2000 to 2012 in the "Amiantus" prophylactic medical examination program; average time since exposure ended was 16.5 years and mean duration of employment was 11.5 years
• Exposure: Dust from asbestos-cement production. The products contained 9% to 12% asbestos and were made with chrysotile, occasionally with up to 5% crocidolite added; crocidolite was banned from the mid-80s. Cumulative exposure to asbestos-containing dust was estimated from a job exposure matrix built on gravimetric respirable dust measurements, expressed in mg/m3·yr (mean 31.5, standard deviation 31.7).
• Main results:
  • Among all 3005 workers, restrictive ventilation disorders were found in 21.6%, obstructive in 8.3% and mixed in 7%
  • Workers with higher cumulative exposure had lower mean FEV1, FVC and FEV1/FVC than less-exposed workers. In the over-60 mg/m3·yr group compared with the under-21 group, the differences were 0.109 L lower FEV1 (P less than 0.001), 0.085 L lower FVC (P = 0.010) and 1.33% lower FEV1/FVC (P = 0.008), per the article's Table 2
  • FEV1 declined more slowly, by 0.046 L per 10 years, in workers with cumulative exposure over 60 mg/m3·yr than in those under 21 mg/m3·yr. The P value was 0.053, above the study's 0.05 significance level.
  • The 10-year decline in FEV1/FVC was 1.02% smaller in workers with cumulative exposure over 60 mg/m3·yr than in those under 21 mg/m3·yr (P = 0.027 in Table 3)
  • The 10-year decrease in FEV1 was 0.091 L greater in workers smoking 11 to 50 cigarettes a day than in nonsmokers (P less than 0.001)
  • Compared with nonsmokers, FEV1/FVC dropped faster in smokers: by 1.01% per 10 years (P = 0.028) for up to 10 cigarettes a day, and by 1.45% per 10 years (P less than 0.001) for more than 10 a day
  • Compared with workers whose exposure ended less than 11 years earlier, FEV1/FVC fell faster: by 1.27% per 10 years when exposure had ended 11 to 30 years earlier, and by 2.62% per 10 years when it had ended more than 30 years earlier (both P less than 0.001). Time since exposure ended was not significantly linked to the rate of decline in FEV1 or FVC (Table 3).
  • Workers with asbestosis had lower FEV1 levels. Those with small opacity profusion category 2/1 and higher had slower declines than workers with category 0/0 to 0/1: by 0.160 L per 10 years in FEV1 (P = 0.036) and by 3.17% per 10 years in FEV1/FVC (P = 0.031)
• The authors' conclusion: The authors concluded that asbestos-cement workers with higher cumulative exposure still had significantly lower mean FEV1, FVC and FEV1/FVC many years after exposure ended. They also concluded that the rates of decline in FEV1 and FEV1/FVC were not faster among those with higher exposure.
• Limitations the authors state:
  • Participants came forward voluntarily, possibly because they wanted an occupational disease diagnosis and compensation, or because they were in worse health
  • Exposure was assessed from retrospective gravimetric respirable dust measurements rather than fiber counts, because fiber counting began only in the mid-80s
  • The results cannot be generalized to other branches of asbestos processing, because the asbestos fiber content of dust differed between product types
  • The study relied only on spirometry, which is not the same as disorders of lung function; total lung capacity is the best measurement to confirm restriction

Topics

Medical terms in this study, explained in our Lexicon: Spirometry, Asbestos-Cement, FEV1, FEV1/FVC Ratio, Cumulative Exposure, Asbestos Exposure.

Related studies

• Radiological changes in asbestos cement workers — K. Jakobsson, U. Strömberg, et al. (1995)
• Lung function in relation to radiographic changes in asbestos workers — S. Zedda, G. Aresini, et al. (1973)
• Cancer risk after cessation of asbestos exposure: a cohort study of Italian asbestos cement workers — C. Magnani, D. Ferrante, et al. (2008)
• Spirometry: a predictor of lung cancer among asbestos workers — B. Świątkowska, N. Szeszenia-Dąbrowska (2017)
• Asbestos in Poland: occupational health problems — N. Szeszenia-Dąbrowska, B. Swiątkowska, et al. (2011)
• Mortality and cancer morbidity in cohorts of asbestos cement workers and referents — M. Albin, K. Jakobsson, et al. (1990)

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