Irregular opacities in the lung, occupational asthma, and airways dysfunction in aluminum workers

Our plain-English summary of Irregular opacities in the lung, occupational asthma, and airways dysfunction in aluminum workers, by K.H. Kilburn, R.H. Warshaw (American Journal of Industrial Medicine, 1992).

The study

• Authors: K.H. Kilburn, R.H. Warshaw
• Journal: American Journal of Industrial Medicine
• Published: 1992;21(6):845-53
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 004906).

Abstract

We examined chest X-rays, measured expiratory flows and FVC by spirometry and TLC by projected lung area, ascertained respiratory data by questionnaires, and performed chest examinations in 670 Southeastern aluminum workers and 659 unexposed regional controls. Both groups were asbestos exposed. More aluminum workers had irregular opacities and fewer had pleural abnormalities than did regional pipefitter referents. The pulmonary function tests were expressed as percentage of predicted to adjust for height, age and duration of smoking based on a randomly selected U.S. reference population. Data from aluminum workers were compared to regional controls with students "t" tests run for unequal size groups. Aluminum workers had significant reductions in FEV1 of 3.2% predicted (p less than .003), FEF25-75 of 11.3% predicted (p less than .0001), FEF75-85 of 22.5% predicted (p less than .0001), and an increased TLC of 2.0% predicted (p less than .005). The 145 who had never smoked (NS) were compared with 124 NS controls and showed this same pattern of differences; but in smokers, the differences were significant for mid and terminal flows, but not for FEV1. In aluminum workers who never smoked, asthma prevalence by history was 7.6% vs. 4.0% in controls, and wheezes were heard in 21.4% vs. 2.4% in controls. In aluminum workers who were current smokers, asthma prevalence was 16.4% vs. 9.4% in controls, and wheezes were heard in 43.7% vs. 21.1% in controls. Aluminum workers had significantly more asthma, wheezing, airways obstruction, and pulmonary parenchymal abnormalities similar to asbestosis than did regional blue collar controls not melting and casting aluminum.

In plain English

This exploratory case-match study compared 670 aluminum workers from a union at Muscle Shoals, Alabama, with 659 regional pipefitters who were not exposed to aluminum. Both groups had worked with asbestos. The article does not name the asbestos fiber type. Workers answered questionnaires, had chest examinations and chest X-rays, and did breathing tests. Irregular opacities in the lungs (ILO profusion 1/0 or greater) were found in 20.7% of aluminum workers versus 15.2% of pipefitters. Pleural abnormalities were found in 2.1% versus 11.9%. Reported asthma was 13.5% versus 8.7%, and wheezing heard on examination was 32% versus 11.8%. Among never-smokers, aluminum workers had lower airflow, including FEV1. Among current smokers, mid and terminal flows were lower, but FEV1 did not differ. In 57 aluminum workers without X-ray signs of asbestosis who were tested before and after a Monday shift, 18 (32%) had a 10% or greater drop in mid-flow. The authors favored asbestos as the explanation for the opacities. They concluded that aluminum refining causes obstructive lung disease and may also cause irregular opacities. They noted that participants could not be compared with non-participants.

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: Exploratory case-match (cross-sectional comparison) study of two worker groups
• Who was studied: 670 aluminum refinery workers, members of the Aluminum, Brick, and Glass Workers International Union at Muscle Shoals, Alabama, compared with 659 local pipefitters (United Associated of Plumbers and Pipefitters). Members of both groups were at least 15 years from first occupational asbestos exposure and had at least 5 years of exposure. Ages centered in the mid-50s. Studied around 1989.
• Exposure: Aluminum refinery work. Potrooms made aluminum from 1940 until 1986, and after that the plant only remelted metal. Asbestos was used to insulate the electrolytic pots. The comparison pipefitters were exposed to asbestos, ferrous metal welding and copper brazing, but not to aluminum. The asbestos fiber type is not specified.
• Main results:
  • Irregular lung opacities of ILO profusion 1/0 or greater were seen in 20.7% of aluminum workers versus 15.2% of pipefitter referents.
  • Pleural abnormalities were less common in aluminum workers: 2.1% versus 11.9% in referents.
  • In aluminum workers, the opacities formed an evenly distributed pattern of fine opacities from the top to the bottom of the lungs.
  • Reported asthma was 13.5% in aluminum workers versus 8.7% in referents (7.6% versus 4.0% among never-smokers).
  • Wheezing heard on physical examination was 32% in aluminum workers versus 11.8% in referents (21.4% versus 2.4% among never-smokers). The authors reported this difference as significant.
  • In 145 never-smoking aluminum workers, airflows including FEV1 were significantly lower than in never-smoking controls. FVC and TLC did not differ.
  • In 294 currently smoking aluminum workers, mid-flow and terminal-flow were significantly lower than in referents. FVC, FEV1 and TLC did not differ.
  • 57 aluminum workers without X-ray signs of asbestosis had spirometry before and after a Monday shift. Of these, 18 (32%) had a 10% or greater fall in mid-flow over the shift.
  • In interpreting the irregular opacities, the authors favored asbestos as the explanation.
• The authors' conclusion: The authors concluded that aluminum refining causes obstructive lung disease and may also cause irregular opacities.
• Limitations the authors state:
  • The volunteers studied could not be compared with non-participants to check whether they were representative.
  • Aluminum workers were not divided by potroom or other specific exposure, or by trade.
  • Workplace sampling at the time of study was judged unlikely to give relevant levels of asbestos, aluminum or fluorine exposure.
  • The data cannot answer whether aluminum or its oxides alone can cause fibrosis.
  • The data cannot determine whether exposure to molten aluminum is the only cause of the occupational asthma.
  • The cross-shift results may be biased by workers selecting themselves for that test.

Topics

Medical terms in this study, explained in our Lexicon: Chest X-Ray, Spirometry, Pipefitter, Pulmonary Function Test (PFT), FEV1.

Related studies

• Airway obstruction in asbestos-exposed shipyard workers: with and without irregular opacities — K.H. Kilburn, R.H. Warshaw (1990)
• Effect of tobacco smoking on the presence of asbestosis at postmortem and on the reading of irregular opacities on roentgenograms in asbestos-exposed workers — A. Kraut, J. Godbold, et al. (1989)
• Relation of occupational exposure to respiratory symptoms and asthma in a general population sample: self-reported versus interview-based exposure data — P.S. Bakke, R. Hanoa, et al. (2001)
• Progression of irregular opacities in asbestos miners — G.K. Sluis-Cremer, E. Hnizdo (1989)
• Effect of tobacco smoking on the presence of asbestosis at postmortem and on the reading of irregular opacities on roentgenograms in asbestos-exposed workers — E. Hnizdo, G.K. Sluis-Cremer (1988)
• Cigarette smoking and small irregular opacities — W. Weiss (1991)

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