Ventilatory decrements in former asbestos cement workers: a four year follow up

Our plain-English summary of Ventilatory decrements in former asbestos cement workers: a four year follow up, by C.G. Ohlson, L. Bodin, T. Rydman, et al (British Journal of Industrial Medicine, 1985).

The study

• Authors: C.G. Ohlson, L. Bodin, T. Rydman, C. Hogstedt
• Journal: British Journal of Industrial Medicine
• Published: 1985;42(9):612-6
• Cited by: 48 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000500).

Abstract

A four year follow up of the ventilatory function in former asbestos cement workers has been performed to determine whether any further decrease occurred after cessation of exposure. Seventy five of 125 subjects were eligible for re-examination and were compared with local referents. None showed signs of asbestosis but 32% had pleural plaques at the renewed examination. Cumulative asbestos exposure calculated as fibre x years had been estimated individually in the original examination. After adjustment for age, height, tracheal area, and smoking category the FVC and FEV1 for all exposed subjects were on average 7% v 6% less than predicted from the referents and twice as much for the subjects with the highest exposure. The four year declines in FVC and FEV1 were larger than in the referents, significantly so for FEV1. There were no significant correlations between pleural plaque and ventilatory function after adjustment for exposure. Thus the age adjusted reduction in ventilatory function had progressed during the follow up period despite the cessation of exposure and the lack of radiological signs of asbestosis.

In plain English

This Swedish study followed men who had worked at least ten years at an asbestos cement plant that closed in 1976. The asbestos used was mostly chrysotile, with a few hundred tons of crocidolite and amosite used earlier. Of 125 workers tested in 1976, 75 were retested in 1980. They were compared with 56 referents from three local plants without asbestos exposure. Men who had stopped smoking since 1976 were excluded. None of the former workers showed signs of asbestosis, but 32% had pleural plaques. In 1980, workers in the highest cumulative exposure group had FVC and FEV1 (breathing test measures) of 88.1% and 85.8% of the values predicted from the referents, against 98.3% and 99.8% in the lowest group. Over four years, lung function fell more in former workers than in referents. The link with exposure was statistically significant for FEV1. After adjustment, pleural plaques showed no statistically significant link with lung function. The authors concluded that lung function loss had progressed even though exposure had stopped. They noted that a different breathing test machine was used in 1980.

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: Four year follow-up (longitudinal) study of lung function in former asbestos cement workers compared with unexposed referents
• Who was studied: Male asbestos cement workers at a plant in the middle of Sweden, all with at least ten years of employment. In 1976 there were 125 (77 smokers, 48 never smokers); 75 (43 smokers, 32 never smokers) were included in the 1980 follow-up. Referents came from three plants without asbestos exposure (fertiliser, cement products and wood products): 76 in 1976 and 56 in 1980.
• Exposure: Mostly chrysotile, with a few hundred tons of crocidolite and amosite used earlier. Average fibre concentrations were estimated at about 2 fibres/ml in the 1950s and 1960s and 1 fibre/ml in the 1970s. Cumulative exposure was estimated for each person in fibre-years (range 0 to 60).
• Main results:
  • At the 1980 examination, none of the exposed subjects showed signs of asbestosis, and 32% had pleural plaques.
  • In 1980, exposed subjects in the lowest exposure category had FVC and FEV1 of 98.3% and 99.8% of the values predicted from the referents. The highest exposure category had 88.1% and 85.8% (test for linear trend p = 0.04 and 0.007).
  • The four year decrements were larger in the exposed subjects than in the referents. As a percentage of 1976 volumes, FVC fell 6.6% and FEV1 fell 7.0% in all exposed subjects, against 4.5% and 5.6% in the referents. In the highest exposure group the falls were 8.2% and 8.7% (trend p = 0.06 for FVC and 0.03 for FEV1).
  • Within the exposed group, cumulative exposure affected both lung function measures in the adjusted analysis, but this was statistically significant only for FEV1 (p = 0.02). Smoking had a stronger influence (p less than 0.01).
  • After adjustment for exposure, there were no statistically significant correlations between pleural plaques and lung function.
• The authors' conclusion: The authors concluded that the age adjusted reduction in lung function had progressed during follow-up despite the end of exposure and the absence of radiological signs of asbestosis. They judged the loss probably clinically significant so far only for the most highly exposed subjects.
• Limitations the authors state:
  • A different spirometer was used in 1980, and only the second one was properly calibrated. The authors said the first may have given too large volumes, which could affect the size of the differences found.
  • The referents' decline was greater than expected. The authors suggested their exposure to industrial pollutants might explain this, in which case the effect of asbestos cement exposure would be underestimated.
  • Ex-smokers were excluded, and more exposed subjects than referents became ex-smokers during follow-up. The authors checked this possible source of bias and judged that it had not distorted the results.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Pleural Plaques, Asbestos Exposure, FEV1.

Related studies

• Decreased lung function in long-term asbestos cement workers: a cross-sectional study — C.G. Ohlson, T. Rydman, et al. (1984)
• Mortality of workers in a French asbestos cement factory 1940-82 — A.M. Alies-Patin, A.J. Valleron (1985)
• Lung function predicts mortality: 10-year follow-up after lung cancer screening among asbestos-exposed workers — T. Vehmas, P. Pallasaho, et al. (2013)
• Ventilatory function after exposure to various respirable hazards in a population of former coal miners — G.M. Calvert, M. Moore, et al. (1991)
• Genetic polymorphism for glutathione-S-transferase mu in asbestos cement workers — K. Jakobsson, A. Rannug, et al. (1994)
• Longitudinal pattern of reported respiratory symptoms and accelerated ventilatory loss in asbestos-exposed workers — C.A. Brodkin, S. Barnhart, et al. (1996)

Browse more research in British Journal of Industrial Medicine, or return to medical research.