Lung function in insulation workers

Our plain-English summary of Lung function in insulation workers, by J. Clausen, B. Netterstrøm, C. Wolff (British Journal of Industrial Medicine, 1993).

The study

• Authors: J. Clausen, B. Netterstrøm, C. Wolff
• Journal: British Journal of Industrial Medicine
• Published: 1993;50(3):252-6
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

To evaluate the effects of working with modern insulation materials (rock and glass wool), the members of the Copenhagen Union of Insulation Workers were invited to participate in a study based on a health examination that included lung function tests. Three hundred and forty men (74%) agreed to participate, and 166 bus drivers served as the control group. Age distribution, height, and smoking habits were similar in the two groups. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were used as tests for lung function. There were no differences in FVC between the study and control groups, but the insulation workers had significantly lower values of FEV1 (mean 2.51) compared with the controls (mean 3.4 1), independent of smoking habits. Six years before the present study, 114 of the insulation workers participated in a similar study, and eight years after the initial study, the lung function of 59 of the bus drivers was tested. The decline in FVC in insulation workers who smoked was significantly higher (7.7 cl/year) than in bus drivers who smoked (3.1 cl/year); the decline in FEV1 was significantly higher in insulation workers independent of smoking habits (17.0 cl/year v 2.9 cl/year). Self assessed former exposure to asbestos was not associated with lung function in insulation workers. The study concludes that working with modern insulation materials is associated with increased risk of developing obstructive lung disease.

In plain English

This Danish study compared lung function in insulation workers, who worked mainly with rock and glass wool, with lung function in bus drivers. In the cross sectional part, 340 men from the Copenhagen Union of Insulation Workers (74% of those invited) and 166 bus drivers had forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) measured. Average FVC did not differ significantly between the two groups. Average FEV1 was lower in insulation workers (2.5 v 3.4 litres), and this held in every smoking group. In the follow up part, 114 insulation workers and 59 bus drivers who had been tested years earlier were tested again. FEV1 fell by 17.0 centilitres per year in insulation workers and by 2.9 in bus drivers. Among insulation workers, self assessed former exposure to asbestos was not associated with lung function. The authors concluded that working with modern insulation materials is associated with increased risk of developing obstructive lung disease. They noted possible selection of participants, different testers between rounds, and crude asbestos exposure data.

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 study with a longitudinal (follow up) part, comparing insulation workers with a control group of bus drivers
• Who was studied: Cross sectional part: 340 men from the Copenhagen Union of Insulation Workers (74% of members invited) and 166 bus drivers (83% of those randomly selected), Copenhagen, Denmark. Follow up part: 114 insulation workers tested in a similar study six years earlier, and 59 bus drivers retested eight years after their initial study. Mean age was 42 in both groups in the cross sectional part.
• Exposure: Work with modern insulation materials: dust from glass and rock wool (mineral wool), and occasionally lime containing tetrahydrofuran and polyurethane material containing isocyanates. Earlier measurements cited by the article showed fibre concentrations most often between 0.03 and 1 fibre/ml, with peaks up to 10 fibres/ml during clean up. Former asbestos exposure was self assessed, reported by 67% of insulation workers in the cross sectional part and 88% in the follow up part. Asbestos insulation was banned in Denmark in 1972.
• Main results:
  • Cross sectional part, adjusted for height and age: mean FVC was 4.01 litres in all insulation workers and 4.15 litres in all controls (not significant). Mean FEV1 was 2.50 litres in insulation workers and 3.42 litres in controls (p less than 0.001). The scan prints several of these decimal points as spaces (for example '4 01'). The article's abstract gives the FEV1 means as 2.5 and 3.4 litres.
  • FEV1 was significantly lower in insulation workers than in bus drivers in every smoking category: current smokers 2.50 v 3.35, previous smokers 2.11 v 3.57, never smokers 2.80 v 3.71 litres, each p less than 0.001. Among previous smokers, FVC was also lower in insulation workers (3.44 v 4.32 litres, p less than 0.01). Several of these decimals are printed as spaces in the scan of Table 2.
  • 62 of the 340 insulation workers had FEV1 below 2 litres, compared with 3 of the 166 bus drivers. 12 insulation workers had FEV1 under 1 litre.
  • 66% of insulation workers had a Tiffeneau value (FEV1 as a share of FVC) under 70%, and 16% had values below 50%. Among bus drivers, 14 (9%) had a value under 70%.
  • Follow up part (114 insulation workers, 59 controls): average yearly decline in FVC was 7.7 cl/year in all insulation workers and 3.1 cl/year in all controls (p less than 0.01). Average yearly decline in FEV1 was 17.0 cl/year and 2.9 cl/year respectively (p 0.01). By smoking group, FVC decline differed significantly only among current smokers (9.2 v 2.8 cl/year). FEV1 decline was higher in insulation workers in every smoking group (current 17.5 v 2.2, previous 16.9 v 3.1, never 15.4 v 5.6 cl/year).
  • Among insulation workers, self assessed former exposure to asbestos was not associated with FVC or FEV1 in any smoking group (all differences not significant).
  • Using years worked as an insulation worker as a measure of dose did not establish a dose-response relation. Age was a stronger predictor of low lung function than seniority.
• The authors' conclusion: The authors concluded that working with modern insulation materials is associated with increased risk of developing obstructive lung disease. They also concluded that the effect of tobacco smoking on lung function was almost negligible compared with the effect of working with insulation materials.
• Limitations the authors state:
  • Selection of participants among insulation workers could have caused bias. Few workers with diagnosed asbestosis took part, and of six asbestosis cases in the first study, three died and two did not attend follow up.
  • There was strong health related selection among the bus driver controls because of their job. The authors considered this not especially related to lung disease.
  • Different people carried out the lung function tests in the different studies, which could have influenced results.
  • Asbestos exposure data were crude (self assessed), and asbestos effects may be obscured by exposure to mineral wool and other insulation materials.
  • The degree of exposure could hardly be differentiated, because most insulation workers worked at several worksites doing different tasks.
  • Information on the bus drivers' exposure to asbestos was not available.

Topics

Medical terms in this study, explained in our Lexicon: Insulator, Habit, FEV1, Obstructive Lung Disease.

Related studies

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• Decreased lung function in long-term asbestos cement workers: a cross-sectional study — C.G. Ohlson, T. Rydman, et al. (1984)
• The relative importance of clinical, radiological and pulmonary function variables in evaluating asbestosis and chronic obstructive airway disease in asbestos workers — G.M. Regan, B. Tagg, et al. (1971)
• Respiratory health of workers exposed to metal dusts and foundry fumes in a copper refinery — G. Ostiguy, C. Vaillancourt, et al. (1995)
• Relationship between chest X-ray findings and pulmonary function tests in dust workers — Y. Tonori, M. Niitsuya, et al. (2005)
• Ethnic differences in lung function: evidence for proportional differences — C.E. Rossiter, H. Weill (1974)

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