Surface of localized pleural plaques quantitated by computed tomography scanning: no relation with cumulative asbestos exposure and no effect on lung function

Our plain-English summary of Surface of localized pleural plaques quantitated by computed tomography scanning: no relation with cumulative asbestos exposure and no effect on lung function, by J. Van Cleemput, H. De Raeve, J.A. Verschakelen, et al (American Journal of Respiratory and Critical Care Medicine, 2001).

The study

• Authors: J. Van Cleemput, H. De Raeve, J.A. Verschakelen, J. Rombouts, L.M. Lacquet, B. Nemery
• Journal: American Journal of Respiratory and Critical Care Medicine
• Published: 2001;163(3 Pt 1):705-10
• Cited by: 48 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

To evaluate if there is a relation between the size of asbestos plaques and the level of past exposure and pulmonary function, we measured the surface of localized pleural plaques found on high-resolution (HR) CT scan, using a computerized video display unit-imaging system, in 73 workers (mean age, 43.5 yr) who had worked from 23 to 27 yr in an asbestos-cement factory. Their estimated cumulative exposure to asbestos ranged from 16.4 to 98.7 fiber-years/ ml (mean, 26.3 fiber-years/ml). Lung function measurements included lung volumes, maximal expiratory flows, and diffusing capacity. A control group of 21 workers was examined by the same procedures. Plaques were detected by CT in 51 (70%) asbestos-exposed subjects and in none of the control subjects. The average calculated plaque surface was 47.9 +/- 61.7 cm2 (median, 22.1 cm2; range, 0 to 278.4 cm2). There was no relation between plaque surface and cumulative asbestos exposure (p = 0.24). In the 51 subjects with pleural plaques, the surface of the pleural lesions was not related to cumulative asbestos exposure, or to smoking history or time since first exposure. Neither the presence nor the extent of the plaques was correlated with lung function parameters.

In plain English

The authors asked whether localized pleural plaque size reflects past exposure or affects lung function. They studied 73 male asbestos-cement workers employed 23 to 27 years, many exposed to chrysotile as well as amphibole asbestos, and 21 hospital cleaning and catering workers in Leuven, Belgium. Estimated cumulative exposure, excluding the last 5 years, was 16.4 to 98.7 fiber-years/ml (mean 26.3). CT found plaques in 51 (70%) exposed workers and no controls, and chest X-rays found them in 19 (26%). Mean total plaque surface across all 73 exposed workers, including those without plaques, was 47.9 cm2 (median 22.1). Plaque surface was not significantly related to cumulative exposure (p = 0.24). No worker showed clear signs of asbestosis. Lung function did not differ significantly between exposed workers and controls or between those with and without plaques, and did not correlate with plaque size. The authors concluded that in these workers, whose plaques were moderate in surface, those with larger plaques had neither higher cumulative exposure nor poorer lung function. They noted that early exposure estimates may be overestimated and that plaque size and exposure varied rather little.

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 of a cohort of asbestos-cement workers compared with a control group, using CT scans, chest X-rays and lung function tests
• Who was studied: 73 male workers from an asbestos-cement factory, born 1945 to 1954, hired 1965 to 1969, with at least 2 years of employment. They were scanned between June 1991 and May 1994 and came from a cohort of 88. Mean age was 43.5 years. Controls were 21 male workers of similar age from the cleaning or catering departments of the University Hospitals, Leuven, Belgium.
• Exposure: Work in an asbestos-cement factory. Many workers in the cohort were exposed to chrysotile as well as amphibole asbestos. Duration was 23 to 27 years. Estimated cumulative exposure, excluding the last 5 years, ranged from 16.4 to 98.7 fiber-years/ml (mean 26.3), calculated from job category and calendar period.
• Main results:
  • CT found localized pleural plaques in 51 (70%) of the 73 asbestos-exposed workers and in none of the 21 control subjects.
  • Chest X-ray found plaques in 19 (26%) of the exposed workers. Compared with CT, the chest X-ray's sensitivity was 33%.
  • Across the whole exposed group of 73 workers, including the 22 without plaques on CT, the mean total plaque surface (costal, diaphragmatic and mediastinal) was 47.9 cm2. The standard deviation was 61.7 cm2 (median 22.1 cm2; range 0 to 278.4 cm2).
  • There was a small tendency for total plaque surface to increase with cumulative exposure, but it was not statistically significant (p = 0.24, Spearman rank correlation).
  • Workers with less than 25 fiber-years/ml had a mean plaque surface of 46.2 cm2 (median 16.8). Those with more than 25 fiber-years/ml had a mean of 50.6 cm2 (median 34.9). The difference was not significant.
  • Among the 51 workers with plaques, multiple regression found no correlation between plaque surface and cumulative asbestos exposure (p = 0.94), pack-years of smoking (p = 0.37), or time since first exposure (p = 0.15).
  • No asbestos worker showed clear signs of asbestosis, and no ILO profusion score was above 1/0.
  • Lung function did not differ significantly between asbestos-exposed workers and controls. The 51 workers with plaques did not differ significantly from the 22 exposed workers without plaques. Plaque surface was not significantly correlated with lung function after accounting for pack-years and fiber-years.
  • Smoking significantly affected FEV1 in the expected direction.
• The authors' conclusion: The authors concluded that in these workers with circumscribed pleural plaques of moderate surface, those with larger plaques did not have higher past cumulative asbestos exposure or poorer lung function.
• Limitations the authors state:
  • Before 1978, measurements were mostly static samples taken near the exposure source during peak activity. Combining them with later personal monitoring may have considerably overestimated exposures.
  • Because many workers were exposed to both chrysotile and amphibole asbestos, the study cannot address differences between fiber types.
  • Variation in both plaque size and exposure intensity was rather limited, which may explain the lack of a significant correlation.
  • By design, time since first exposure differed by at most 5 years between subjects.
  • The population was relatively young (all under 50), so later development of pulmonary fibrosis cannot be excluded.
  • Detecting and measuring diaphragmatic plaques on CT slices was problematic because of their orientation.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Plaques, Asbestos Exposure, CT Scan, Asbestos-Cement, Cumulative Exposure, Fiber Year, Diffusing Capacity (DLCO).

Related studies

• Findings from high resolution computed tomography of the lung and pleura of symptom free workers exposed to amosite who had normal chest radiographs and pulmonary function tests — S. Neri, A. Antonelli, et al. (1994)
• Focal pleural thickening mimicking pleural plaques on chest computed tomography: tips and tricks — K.M. Alfudhili, D.A. Lynch, et al. (2016)
• Observer variation in computed tomography of pleural lesions in subjects exposed to indoor asbestos — H. De Raeve, J.A. Verschakelen, et al. (2001)
• High-resolution computed tomography abnormalities in ex-insulators annually exposed to asbestos dust — J.M. Soulat, D. Lauque, et al. (1999)
• High resolution computed tomography and lung function in asbestos-exposed workers with normal chest radiographs — C.A. Staples, G. Gamsu, et al. (1989)
• Pulmonary function, smoking habits, and high resolution computed tomography (HRCT) early abnormalities of lung and pleural fibrosis in shipyard workers exposed to asbestos — S. Neri, P. Boraschi, et al. (1996)

Browse more research in American Journal of Respiratory and Critical Care Medicine, or return to medical research.