Different measures of asbestos exposure in estimating risk of lung cancer and mesothelioma among construction workers

Our plain-English summary of Different measures of asbestos exposure in estimating risk of lung cancer and mesothelioma among construction workers, by K. Koskinen, E. Pukkala, R. Martikainen, et al (Journal of Occupational and Environmental Medicine, 2002).

The study

• Authors: K. Koskinen, E. Pukkala, R. Martikainen, K. Reijula, A. Karjalainen
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2002;44(12):1190-6
• Cited by: 33 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

To analyze occupation, expert-evaluated cumulative exposure, and radiographic abnormalities as indicators of asbestos-related cancer risk we followed 16,696 male construction workers for cancer in 1990-2000. We calculated standardized incidence ratios (SIR) in comparison to the Finnish population and relative risks (RR) in a multivariate analysis in comparison to the internal low-exposure category of each indicator. Overall, the risk was increased for mesothelioma (SIR 2.0, 95% CI = 1.0-3.3), but not for lung cancer (SIR 1.1, 95% CI = 0.9-1.2). Radiographic lung fibrosis indicated a 2-fold and a high value of the exposure index a 3-fold RR of lung cancer, while there was no risk among those with pleural plaques. The risk of lung cancer was the highest in insulators (RR 3.7, 95% CI = 1.4-9.9). Occupation, expert-evaluated cumulative exposure, and lung fibrosis are useful indicators of lung cancer risk among construction workers.

In plain English

This study followed 16,696 Finnish men, mainly building construction workers, who joined a national asbestos screening campaign in 1990–1992. Their records were linked to the Finnish Cancer Registry through 2000. The authors compared their cancer rates with national rates, and compared risk within the group by occupation, an expert-estimated cumulative asbestos exposure index, and chest X-ray findings. There were 13 mesotheliomas, about twice the national rate (SIR 1.96, 95% CI 1.04–3.35). Lung cancer, with 249 cases, was not significantly raised overall (SIR 1.07, 95% CI 0.94–1.20). Men with X-ray signs of lung fibrosis had 1.9 times the lung cancer risk of men without them (95% CI 1.3–2.7). The highest exposure-index category had 3.3 times the risk of the lowest (95% CI 1.3–8.3). Men with pleural plaques had only a slightly, not significantly, higher risk. Insulators had the highest lung cancer risk, 3.7 times that of construction technicians (95% CI 1.4–9.9). The authors concluded that high-risk subgroups can be identified from exposure and X-ray information. They noted that the few mesotheliomas made firm conclusions about that disease difficult.

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: Cohort follow-up of participants in a screening campaign, linked to the national cancer registry. Cancer rates were compared with the Finnish population (standardized incidence ratios), and relative risks within the cohort were estimated with log-linear models.
• Who was studied: 16,696 men who had worked mainly in building construction in Finland and took part in the 1990–1992 asbestos screening campaign. All had worked at least 10 years in construction. At screening, their mean age was 53 and their mean time in construction was 26 years. They were followed from the screening visit to the end of 2000, giving 149,607 person-years.
• Exposure: Asbestos exposure was measured three ways. (1) Main occupation, such as insulators, plumbers, electricians and carpenters. (2) A cumulative exposure index: years in each type of work multiplied by weighting factors based on past Finnish industrial hygiene measurements. (3) Chest X-ray findings: lung fibrosis (ILO small irregular opacity score of at least 1/0) and pleural plaques. The study did not measure exposure by fiber type.
• Main results:
  • In the whole cohort compared with the Finnish population, there were 13 mesotheliomas (SIR 1.96, 95% CI 1.04–3.35).
  • In the whole cohort compared with the Finnish population, lung cancer was not significantly increased: 249 cases (SIR 1.07, 95% CI 0.94–1.20).
  • Men with an ILO lung fibrosis score of at least 1/0 had a 1.9-fold relative risk of lung cancer (95% CI 1.3–2.7) compared with men without such changes. This figure comes from the multivariate analysis.
  • Men in the highest exposure-index category (about 6% of the cohort) had a 3.3-fold relative risk of lung cancer (95% CI 1.3–8.3) compared with the lowest category. This figure comes from the multivariate analysis.
  • Men with pleural plaques had only a slightly, and not significantly, raised relative risk of lung cancer: RR 1.2, 95% CI 0.9–1.6, in the multivariate analysis.
  • Insulators had the highest relative risk of lung cancer: RR 3.7, 95% CI 1.4–9.9, in the multivariate analysis, compared with construction technicians. Against the Finnish population, their lung cancer SIR was 3.03 (95% CI 1.45–5.56).
  • Mesothelioma was significantly increased among insulators compared with the Finnish population: 3 cases among 334 insulators, SIR 28.9, 95% CI 5.97–84.6.
  • Mesothelioma was also significantly increased among electricians compared with the Finnish population: 4 cases among 2,135 electricians, SIR 9.78, 95% CI 2.66–25.0.
  • Within the cohort, mesothelioma risk rose with the exposure index. In the multivariate analysis it was RR 10.5 (95% CI 3.5–31.3) for the highest category compared with the combined two lowest categories. Risk was lower in men with pleural plaques (RR 0.6, 95% CI 0.3–1.4).
  • About 97% of the lung cancers occurred in current or former smokers. Current smokers had an RR of 35 (95% CI 16–74) compared with nonsmokers.
• The authors' conclusion: The authors concluded that groups with a high risk of lung cancer and mesothelioma can be picked out among long-term construction workers using exposure and X-ray information. In their view, pleural plaques did not identify raised lung cancer risk, while lung fibrosis and a high exposure index did. Job title (insulators) identified the highest risk.
• Limitations the authors state:
  • There were few mesothelioma cases, which made firm conclusions about how mesothelioma risk is spread among construction workers difficult.
  • The exposure index is not an absolute measure of cumulative exposure in fiber-years.
  • The index may not have captured all asbestos exposure, such as bystander exposure. There may also be other confounding exposures in these occupations.
  • The comparison population included many asbestos-exposed people. The authors stated this would bias risk estimates downward, and that the mesothelioma SIR would have been considerably higher against a truly unexposed population.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Lung Cancer, Mesothelioma, Cumulative Exposure, Standardized Incidence Ratio (SIR), Relative Risk, Multivariate Analysis, Fibrosis.

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