Lung fibre burden in lung cancer cases employed in the rock and slag wool industry

Our plain-English summary of Lung fibre burden in lung cancer cases employed in the rock and slag wool industry, by K. Soldan, F.D. Pooley, J. Hansen, et al (The Annals of Occupational Hygiene, 2006).

The study

• Authors: K. Soldan, F.D. Pooley, J. Hansen, A. Andersen, J. Chang-Claude, G. Ferro, H. Ohgaki, B.G. Skov, J.W. Cherrie, R. Saracci, P. Boffetta
• Journal: The Annals of Occupational Hygiene
• Published: 2006;50(3):241-8
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: To evaluate the relationship between estimated exposure to man-made vitreous fibres (MMVF) and to asbestos fibres and their concentration in the lung tissue of lung cancer cases amongst MMVF production workers.

Methods: Retrospective retrieval of available lung tissue specimens was conducted following a case-control study that assessed estimated occupational exposures of MMVF workers. Fibre recovery and analysis by transmission electron microscopy (TEM) were conducted to determine fibre type, fibre dimension and numbers per gram of dry lung tissue. For cases with detailed exposure data, geometric mean (GM) concentrations were compared across the exposure categories, and regression models were used to investigate the relationship between the lung fibres and the variables of estimated exposure, with and without additional variables that may affect fibre retention.

Results: A total of 24 samples from 17 cases of lung cancer were available for analysis: MMVF were detected in all cases. Asbestos fibres were detected in 16. No difference or trend in GM MMVF concentration was observed across the estimated exposure categories. Odds ratio (OR) for MMVF g(-1) dry lung was 0.5 (95% confidence interval: 0.1-2.4) for the second, and 3.5 (0.6-18.9) for the third quartile of index of average exposure to MMVF in industry, compared with the first (lowest exposed) quartile (no cases in the highest quartile).

Conclusions: No observable relationship existed between estimated exposure and directly-measured lung fibres among this sample of cases. Retrospective specimen collection, intra-individual variability in fibre concentration, effect of unknown factors on fibre retention and small sample size militated against this study providing evidence for or against a relationship between estimated exposure and lung fibre concentrations.

In plain English

This study measured fibres in lung tissue from men who worked in rock and slag wool production, a type of man-made vitreous fibre (MMVF), and died of primary lung cancer between 1971 and 1994 (up to 1996 in Denmark). They were cases from an earlier European case–control study. Electron microscopy was used to analyse 24 normal lung samples from 17 cases. They compared results with exposure estimates from job histories and questionnaires, available in detail for 12 cases. MMVF were found in all 17 cases, at 0.27 to 4.29 million fibres per gram of dry lung. Asbestos fibres were found in 16 cases in minor amounts, described by the authors as similar to general-population levels. Lung fibre levels did not follow estimated exposure to MMVF or asbestos, and age, time since exposure and amount smoked did not predict them. All 12 cases with detailed data were smokers, limiting the smoking analysis. The authors concluded there was no evidence of a relationship. They added that the small sample, retrospective collection and variation between samples meant the study could not provide evidence either way.

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: Lung tissue fibre burden analysis (transmission electron microscopy) of retrospectively retrieved specimens from a subset of cases in a previously published nested case–control study, compared with that study's estimated exposure measures
• Who was studied: Male rock and slag wool (RSW) workers in a European cohort who died from primary lung cancer between 1971 and 1994 (up to 1996 in Denmark). Tissue came from 30 cases, of which 17 had normal lung tissue analysed (13 Denmark, 2 Germany, 2 Norway), giving 24 samples. 12 of the 17 had detailed exposure data.
• Exposure: Estimated occupational exposure to MMVF (rock and slag wool) and to asbestos, derived from questionnaires to relatives and factory expert panels. Measured lung fibres included MMVF, amosite, crocidolite, chrysotile and tremolite.
• Main results:
  • MMVF were detected in all 17 cases, ranging from 0.27 to 4.29 million fibres per gram of dry lung tissue. Concentrations exceeded 1 million fibres per gram in 9 of the 17 cases.
  • Asbestos fibres were detected in 16 of the 17 cases. In almost all cases MMVF made up most of the fibres, with only minor quantities of asbestos.
  • The authors stated that asbestos levels in these lungs were low and similar to those observed in the general population.
  • Among the 12 cases with detailed exposure data, the odds ratio for lung MMVF concentration was 0.5 (95% CI 0.1–2.4) for the second quartile and 3.5 (0.6–18.9) for the third quartile of average MMVF exposure in industry, compared with the lowest quartile. No cases fell in the highest quartile.
  • No association was found between estimated exposure to MMVF or asbestos and mean total lung fibre concentrations.
  • Across all 17 cases, regression found no relationship between lung fibre concentration and duration of employment in the MMVF industry.
  • Age, cigarette consumption (cumulative cigarettes smoked) and time since exposure ended showed no effect as predictors of lung fibre concentration.
  • All 12 cases with detailed information were smokers, so smokers could not be compared with nonsmokers.
• The authors' conclusion: The authors concluded that there was no evidence of a relationship between the estimated exposures and directly measured lung fibres in this sample of cases. They added that the study's limitations meant it could not provide evidence for or against such a relationship.
• Limitations the authors state:
  • The small number of subjects gave low statistical power.
  • Because all subjects were smokers, the smoking analysis had little power.
  • Few samples could be obtained retrospectively; at one centre many eligible samples had been incinerated.
  • Where in the lung each specimen came from could not be determined or standardized.
  • Variation between samples from the same person could hide real differences between people and bias results towards no effect.
  • Selection of Danish lungs, which made up 13 of the 17 cases, favoured the more highly exposed cases.
  • There was little diversity in exposure and smoking status.
  • Workers were likely exposed to other MMVF (glass wool and RSW) outside MMVF production.

Topics

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

Medical terms in this study, explained in our Lexicon: Lung Cancer, Vitreous, Case-Control Study, Occupational Exposure, Transmission Electron Microscopy (TEM), Odds Ratio, confidence interval.

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