Occupational asbestos exposure and lung cancer--a systematic review of the literature

Our plain-English summary of Occupational asbestos exposure and lung cancer--a systematic review of the literature, by L.S. Nielsen, J. Bælum, J. Rasmussen, et al (Archives of Environmental & Occupational Health, 2014).

The study

• Authors: L.S. Nielsen, J. Bælum, J. Rasmussen, S. Dahl, K.E. Olsen, M. Albin, N.C. Hansen, D. Sherson
• Journal: Archives of Environmental & Occupational Health
• Published: 2014;69(4):191-206
• Type of article: Systematic review
• Cited by: 84 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The objective of this study was to evaluate the scientific literature concerning asbestos and lung cancer, emphasizing low-level exposure. A literature search in PubMed and Embase resulted in 5,864 citations. Information from included studies was extracted using SIGN. Twenty-one statements were evidence graded. The results show that histology and location are not helpful in differentiating asbestos-related lung cancer. Pleural plaques, asbestos bodies, or asbestos fibers are useful as markers of asbestos exposure. The interaction between asbestos and smoking regarding lung cancer risk is between additive and multiplicative. The findings indicate that the association between asbestos exposure and lung cancer risk is basically linear, but may level off at very high exposures. The relative risk for lung cancer increases between 1% and 4% per fiber-year (f-y)/mL, corresponding to a doubling of risk at 25-100 f-y/mL. However, one high-quality case-control study showed a doubling at 4 f-y/mL.

In plain English

This was a systematic review of published research on occupational asbestos exposure and lung cancer, with emphasis on low-level exposure. It was commissioned by the Danish National Board of Industrial Injuries. The authors searched PubMed and Embase in July 2012 and included 295 citations. Of these, 28 original studies (24 cohort and 4 case-control) reported lung cancer risk in relation to exposure. The authors graded 21 statements by strength of evidence. They rated as strong the evidence that lung cancer cell type and location do not distinguish asbestos-related from other lung cancers. They also rated as strong that the exposure-response relationship is approximately linear but levels off above 150 fiber-years/mL. With moderate evidence, the risk ratio rose by 0.01 to 0.04 per fiber-year/mL, which corresponds to a doubling of risk at 25 to 100 fiber-years/mL. One high-quality Swedish case-control study found a doubling around 4 fiber-years/mL. The authors found no evidence for a no-effect level. They concluded that all asbestos fiber types are associated with lung cancer risk, and that the asbestos-smoking interaction lies between additive and multiplicative. They noted that a single physician did the initial screening of references.

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: Systematic review of the literature, with evidence-graded statements
• Who was studied: Published studies found through PubMed and Embase searches (July 2012) plus reference lists, coauthor input and PubMed alerts: 295 included citations. 28 original studies (24 cohort, 4 case-control) gave lung cancer risk by occupational asbestos exposure.
• Exposure: Occupational asbestos exposure. Among the 28 exposure-response studies: 8 restricted to chrysotile, 7 mainly chrysotile, 1 mainly amosite, 1 amosite alone, 4 amphibole, 4 mixed without stated distribution, 3 type not described. Industries included textile production, mining and/or milling, cement production and insulation.
• Main results:
  • Strong evidence (+++): the more recent, well-controlled studies showed no significant differences in cell type or location between asbestos-related and other lung cancers.
  • Strong evidence (+++): the exposure-response relationship is approximately linear but levels off at very high exposures (above 150 fiber-years/mL).
  • Moderate evidence (++): an increase in risk ratio of 0.01 to 0.04 per fiber-year/mL (doubling of risk at 25 to 100 fiber-years/mL) has been observed. One high-quality population-based case-control study found a doubling around 4 fiber-years/mL.
  • In the Swedish case-control study by Gustavsson et al. 2002, as tabulated in the review, 4 fiber-years/mL was associated with a RR of 1.9 (95% CI 1.32 to 2.74).
  • Moderate evidence (++): no evidence for a no observed effect level for asbestos-related lung cancer. Limited evidence (+): the lowest documented increased risk is at about 4 fiber-years/mL.
  • Pleural plaques increase the likelihood of previous asbestos exposure (++), but cannot be used to estimate the degree of exposure (+++).
  • Strong evidence (+++): all types of asbestos fibers are associated with lung cancer risk. Moderate evidence (++): there is not sufficient evidence to derive different risk estimates for different fiber types.
  • The interaction between asbestos and smoking for lung cancer risk was judged to be between additive and multiplicative.
• The authors' conclusion: The authors concluded that the association between asbestos exposure and lung cancer risk is basically linear but may level off at very high exposures. Many studies show relative risk increases of 1% to 4% per fiber-year/mL (doubling at 25 to 100 fiber-years/mL), though one high-quality study showed a doubling at about 4 fiber-years/mL. They found their results generally in accordance with the Helsinki criteria.
• Limitations the authors state:
  • Only one experienced physician did the initial sorting of references; a team might have produced a more systematic process.
  • Because of time and financial limits, additional articles could not be read and graded by 2 reviewers.
  • Changes over time in asbestos sampling and analysis methods introduced substantial uncertainty and possible exposure misclassification in the underlying studies.
  • Very few of the underlying studies had sufficient information on smoking habits.

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: Asbestos Exposure, Lung Cancer, Systematic Review, Histology, Pleural Plaques, Asbestos Bodies, Relative Risk, Doubling of Risk.

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