Relationships between asbestos exposure and pleural plaques: dose and time effects using fractional polynomials

Our plain-English summary of Relationships between asbestos exposure and pleural plaques: dose and time effects using fractional polynomials, by M. Menant, I. Benlala, I. Thaon, et al (Occupational and Environmental Medicine, 2024).

The study

• Authors: M. Menant, I. Benlala, I. Thaon, P. Andujar, B. Julia, P. Brochard, C. Chouaid, B. Clin, A. Gislard, C. Gramond, C. Paris, J.C. Pairon, F. Delva
• Journal: Occupational and Environmental Medicine
• Published: 2024;81(6):313-319
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: The aim of this study was to confirm the relationship between several parameters of exposure to asbestos and pleural plaques (PP) using data from a large cohort of retired workers occupationally exposed to asbestos in France.

Method: A large screening programme, including high-resolution CT (HRCT) examinations at inclusion and two other HRCT campaigns, was organised from 2003 to 2016 in four regions of France for voluntary, formerly asbestos-exposed workers. Exposure to asbestos has been evaluated by industrial hygienists based on the complete work history. The time since first exposure, the time since last exposure, Cumulative Exposure Index and maximum level of exposure to asbestos, were used in logistic regression using fractional polynomials to model the relationship with PP.

Results: The study included 5392 subjects with at least one HRCT available. There was a significant non-linear effect of time since first exposure, time since last exposure and Cumulative Exposure Index to asbestos on the presence of PP. The risk of PP increased with increasing Cumulative Exposure Index to asbestos adjusted for time since first exposure, age and smoking status. Models also show that PP odds rise with increasing time since first exposure adjusted for cumulative index exposure, age and smoking status. PP odds decrease when time since last exposure increases.

Conclusion: The study provides new data on the link between asbestos exposure and the presence of PP using fractional polynomials with non-linear relationships for time exposure parameters and asbestos exposure parameters.

© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY. Published by BMJ.

In plain English

This study used ARDCO, a French screening programme for retired workers formerly exposed to asbestos at work. Workers joined in 2003 to 2005, with further CT campaigns in 2010 and 2016. It included 5392 people (95.7% men) with at least one high-resolution CT scan. Two expert radiologists read each scan, and industrial hygienists rated exposure from full work histories. The article does not say which fiber types participants were exposed to. Pleural plaques were found in 25% (1348), and in 39.6% of those with a 'high' maximum exposure level. Adjusted for time since first exposure, age and smoking, the odds of plaques rose with cumulative exposure up to about 300 unit-years, then stayed roughly constant. Adjusted for cumulative exposure, age and smoking, they rose with time since first exposure up to about 50 years. The odds fell as time since last exposure increased, up to 30 years. The authors wrote that this appears to show stopping exposure is associated with a lower likelihood of plaques. They cautioned that selective survival bias may partly explain it, particularly among highly exposed workers. They also noted possible memory bias and volunteer recruitment.

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: Analysis of a screening cohort of formerly asbestos-exposed retired workers (ARDCO), using logistic regression with fractional polynomials to relate exposure measures to the presence of pleural plaques on HRCT
• Who was studied: 5392 retired workers previously occupationally exposed to asbestos, from four regions of France (Basse-Normandie, Haute-Normandie, Aquitaine and Rhône-Alpes). They were selected from 14 218 ARDCO cohort members, of whom 5808 had a stored CT and 416 were excluded for incomplete smoking data. Volunteers were recruited October 2003 to December 2005, with additional HRCT campaigns in 2010 and 2016. 95.7% were men; mean age at HRCT was 66.9 years.
• Exposure: Occupational asbestos exposure assessed by industrial hygienists from complete work histories; the article does not say which fiber types participants were exposed to. Each job was rated in one of four intensity categories with coefficients: low 0.01, low intermediate 0.1, high intermediate 1, high 10. The measures were maximum exposure level and a Cumulative Exposure Index (coefficient times years, summed over jobs, in exposure units times years, with no measurement data). Time since first exposure and time since last exposure were also used.
• Main results:
  • Pleural plaques were present in 25% (n=1348) of the 5392 subjects, reaching 39.6% among subjects with a 'high' maximum exposure level.
  • Subjects with pleural plaques had a mean Cumulative Exposure Index of 104.9 unit-years, versus 55.2 unit-years in those without.
  • In Model I (adjusted for time since first exposure, age and smoking), the odds of plaques rose with the Cumulative Exposure Index up to around 300 unit-years. The odds ratio for 300 vs 25 unit-years was 2.55 (95% CI 2.17 to 2.99). Above 300 unit-years the odds ratios appeared roughly constant.
  • In Model I (adjusted for the Cumulative Exposure Index, age and smoking), the odds of plaques rose with time since first exposure up to about 50 years. The odds ratio for 50 vs 10 years was 8.22 (95% CI 3.18 to 21.26).
  • In Model II (adjusted for time since first exposure, age and smoking), 'high intermediate' and 'high' maximum exposure levels, compared with 'low', were significantly associated with plaques. For 'high' versus 'low', the table gives an odds ratio of 6.03 (95% CI 3.82 to 9.52).
  • In Models III and IV, the odds of plaques decreased as time since last exposure increased, for values up to 30 years (reference 0 years). In Model III, the odds ratio for 30 vs 0 years was 0.60 (95% CI 0.44 to 0.82).
• The authors' conclusion: The authors concluded that the study described non-linear relationships between time since first exposure and time since last exposure and the presence of pleural plaques. They wrote that time since last exposure 'appears to show' that cessation of exposure is associated with a decrease in the likelihood of developing plaques, while cautioning that selective survival bias may partly explain this. They suggested that time since cessation could be considered in follow-up and lung cancer screening programmes.
• Limitations the authors state:
  • A selective survival bias may explain part of the time-since-last-exposure finding, because the most exposed people may have died of other asbestos diseases. In that case the conclusion could not be applied to highly exposed subjects.
  • Exposure was reconstructed from work histories, which may involve memory bias.
  • Participants were volunteers, and the most highly exposed may already have been under medical follow-up and not joined. The results may therefore not apply to highly exposed populations.
  • Because HRCT was done at one point in time, time since first exposure may have been overestimated if plaques appeared before the scan.
  • The apparent decrease in the effect of time since first exposure beyond 60 years should be interpreted with caution, given the small number of subjects at those values.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Pleural Plaques, High-Resolution CT (HRCT), Work History, Cumulative Exposure.

Related studies

• Pleural plaques and asbestosis: dose- and time-response relationships based on HRCT data — C. Paris, S. Thierry, et al. (2009)
• Asbestos exposure, pleural plaques and digestive cancers — B. Clin, C. Gramond, et al. (2025)
• Deep Learning for the Automatic Quantification of Pleural Plaques in Asbestos-Exposed Subjects — I. Benlala, B.D. De Senneville, et al. (2022)
• Do asbestos-related pleural plaques on HRCT scans cause restrictive impairment in the absence of pulmonary fibrosis? — B. Clin, C. Paris, et al. (2011)
• Asbestos exposure, pleural plaques, and the risk of death from lung cancer — J.C. Pairon, P. Andujar, et al. (2014)
• Fractional exhaled nitric oxide concentration is increased in asbestosis and pleural plaques — A. Sandrini, A.R. Johnson, et al. (2006)

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