Asbestos-related disease in railroad workers. A cross-sectional study

Our plain-English summary of Asbestos-related disease in railroad workers. A cross-sectional study, by L.C. Oliver, E.A. Eisen, R.E. Greene, et al (The American Review of Respiratory Disease, 1985).

The study

• Authors: L.C. Oliver, E.A. Eisen, R.E. Greene, N.L. Sprince
• Journal: The American Review of Respiratory Disease
• Published: 1985;131(4):499-504
• Cited by: 39 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. 000501).

Abstract

A cross-sectional prevalence study of 377 railroad workers was carried out. The purpose was to investigate the prevalence of asbestos-related disease. We compared conventional with more recently adopted criteria for defining abnormal lung function. We compared the test results of those who performed reproducibly on spirometry with those who did not. Medical and occupational histories, flow-volume loops, and posteroanterior and lateral chest radiographs were obtained. Single-breath carbon monoxide diffusing capacity (DLCO) was measured, and chest auscultation was performed. Related to time since onset of exposure, pleural plaques occurred in 22.9%. There was radiographic evidence of interstitial disease in 1.6%. Reduced single-breath DLCO (12.4%), crackles (18.4%), and dyspnea (49.6%) were significantly associated with asbestos exposure. The prevalence of restriction and obstruction was 5.1 and 12.4%, respectively, but differed (p = 0.0001) with the definition criteria selected. The proportion with each of these abnormalities was higher in the nonreproducible group. That group was older, with more pleural plaques and chronic bronchitis. Railroad workers are a group at risk for asbestos-related disease. Extent of disease and assumptions about causality are likely to vary with definitions of normalcy and the use of reproducibility criteria.

In plain English

This cross-sectional study, carried out in March 1982, examined volunteer active and retired workers at a central Pennsylvania railroad yard. The analysis covered 377 white men. Lacking asbestos measurements, the authors built an exposure index from years worked, weighting pre-1956 work most heavily. On chest X-rays, 86 men (22.9%) had definite asbestos-related pleural thickening. Pleural plaques were linked to high versus low exposure and to time since hire; no one hired after the steam era had them. Six men (1.6%) had small irregular lung-tissue shadows. Breathlessness, reduced gas transfer and characteristic crackles were significantly associated with asbestos exposure. Among men with reproducible tests, restricted and obstructed breathing were not; with everyone included, obstruction was significantly associated (p = 0.0463), restriction was not. Counts of restriction and obstruction depended on the definition of abnormal used. The 26% with nonreproducible breathing tests were older, more exposed and had more pleural plaques. The authors concluded the study provides evidence of asbestos-related disease in US railroad workers, despite weaknesses including voluntary participation, no exposure monitoring, similar exposures and no control 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: Cross-sectional morbidity (prevalence) study with questionnaires, lung function tests, chest radiographs and physical examination; no control group
• Who was studied: Volunteer workers at a central Pennsylvania railroad yard examined in March 1982: 182 of 422 active machinists (43.1%) and 191 of 607 retired workers (31.5%). Six people were omitted (women, a nonwhite man, and a man with household contact only), leaving 377 white men for analysis.
• Exposure: Asbestos in railroad shops (fiber type not stated), especially from asbestos-insulated steam locomotive boilers before the end of the steam era, with other sources such as brake shoes, gaskets and gloves. There was no industrial hygiene monitoring. A cumulative exposure index weighted each year worked before 1956 by 4, 1956 through 1958 by 2, and 1959 and later by 1. Workers were also exposed to welding fumes, silica and coal dust.
• Main results:
  • Of the readable chest radiographs (two were unreadable), definite asbestos-related pleural thickening was seen in 86 (22.9%), suspect thickening in 99 (26.4%) and calcification in 29 (7.7%).
  • Pleural plaques were not associated with asbestos exposure treated as a continuous index after adjusting for age and smoking (p = 0.1962).
  • Pleural plaques were associated with high (index greater than 15) versus low (index 15 or less) exposure, controlling for age and smoking (p = 0.0464).
  • Pleural plaques were associated with time since hire, taking age and smoking into account (p = 0.0070).
  • No one hired after the steam engine era had pleural plaques.
  • Six subjects (1.6%) had small, irregular parenchymal (lung tissue) opacities on chest radiograph. The authors said this number was too small for statistical analysis.
  • Dyspnea (breathlessness) remained significantly associated with asbestos exposure after controlling for smoking (p = 0.0001, n=361). Chronic bronchitis did not (p = 0.218).
  • Low single-breath DLCO (gas transfer) was found in 34 (12.4%) of the reproducible group and 18 (17.6%) of the nonreproducible group. Reduced DLCO was significantly correlated with asbestos exposure after adjusting for smoking (p = 0.0007, n=358).
  • Characteristic crackles at 2 or more sites on chest examination were significantly associated with asbestos exposure (p = 0.0001).
  • Among subjects with reproducible tests, neither restriction nor obstruction was significantly associated with asbestos exposure, controlling for smoking and age.
  • The authors reported that excluding the nonreproducible subjects weakened the associations with asbestos exposure. For restriction the p value was 0.2972 with everyone included versus 0.7335 with them excluded. For obstruction it was 0.0463 versus 0.1803.
  • In the reproducible subgroup, restriction was found in 14 (5.1%) using 95% confidence interval criteria and 23 (8.4%) using percent-of-predicted criteria. Obstruction was found in 34 (12.4%) and 45 (16.4%) respectively. The difference between definitions was significant (p = 0.0001).
  • For 98 participants (26%), spirometry results did not meet American Thoracic Society reproducibility criteria. This nonreproducible group was older, with higher asbestos exposure, more chronic bronchitis and more pleural plaques.
  • Chest radiographs revealed lung masses later diagnosed as lung cancer in 4 participants. No cases of mesothelioma were found among participants.
• The authors' conclusion: The authors concluded that, despite potential weaknesses, the study provides evidence of asbestos-related disease among US railroad workers. They also concluded that the prevalence of pleural plaques was similar to that reported among heavily exposed workers in other industrial settings.
• Limitations the authors state:
  • Possible selection bias from voluntary participation; nonparticipants were not characterized
  • Lack of environmental monitoring data, so exposure levels to asbestos and other dusts could not be determined
  • Homogeneity of asbestos exposure in the study population, making exposure-response associations hard to show statistically
  • Non-asbestos exposures (such as silica and welding fumes) may have contributed to respiratory symptoms and abnormal lung function
  • No control group was studied

Topics

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

Medical terms in this study, explained in our Lexicon: Spirometry, Chest X-Ray, Diffusing Capacity (DLCO), Pleural Plaques, Interstitial, Dyspnea, Asbestos Exposure.

Related studies

• Railroad workers with pleural plaques: I. Spirometric and nitrogen washout investigation on smoking and nonsmoking asbestos-exposed workers — U. Hjortsberg, P. Orbaek, et al. (1988)
• Roentgenographic evidence of asbestos exposure in a select population of railroad workers — M.J. Sepulveda, J.A. Merchant (1983)
• Decreased lung function in long-term asbestos cement workers: a cross-sectional study — C.G. Ohlson, T. Rydman, et al. (1984)
• Asbestos-related mesothelioma risk among railroad workers — M. Huncharek (1987)
• Are the knowledge of non-malignant asbestos-related diseases and lung function impairment differentially associated with psychological well-being? A cross-sectional study in formerly asbestos-exposed workers in Germany — J. Lang, M.K. Felten, et al. (2019)
• A case-control study of lung cancer and diesel exhaust exposure in railroad workers — E. Garshick, M.B. Schenker, et al. (1987)

Browse more research in The American Review of Respiratory Disease, or return to medical research.