Asbestos exposure and laryngeal cancer: an analysis of the epidemiologic evidence

Our plain-English summary of Asbestos exposure and laryngeal cancer: an analysis of the epidemiologic evidence, by C.K. Chan, J.B. Gee (Journal of Occupational Medicine., 1988).

The study

• Authors: C.K. Chan, J.B. Gee
• Journal: Journal of Occupational Medicine.
• Published: 1988;30(1):23-7
• Type of article: Review
• Cited by: 33 articles, as counted by NIH iCite
• Read it: PubMed
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000200).

Abstract

We conducted a critical analysis of the available epidemiologic investigations on the causal relationship between asbestos exposure and laryngeal cancer. A review of nine case-control studies indicates that the estimated risk (odds ratio) attributable to asbestos exposure alone is negligible when smoking and ethanol intake are appropriately controlled for. Six of the 12 cohort studies demonstrated no significant increase in the standardized mortality ratio due to asbestos exposure. The remaining six longitudinal studies showed an increased standardized mortality ratio from 1.91 to 5.41 but no adjustment was made for the confounding effects of smoking and ethanol consumption. In conclusion, the available epidemiologic evidence does not support a causal association between asbestos exposure and laryngeal cancer.

In plain English

This 1988 article was a review, not a new study. The authors analysed published English-language epidemiologic studies on whether asbestos exposure causes laryngeal cancer (cancer of the voice box). They focused on whether each study accounted for cigarette smoking and alcohol, which they described as the two most important known risk factors for this cancer. They reviewed nine case-control studies, 12 cohort studies and one case series. In the five case-control studies that adjusted for smoking and alcohol, the authors judged the risk from asbestos alone to be negligible. In one of these, an odds ratio of 1.75, not statistically significant before adjustment, became one after adjustment. Four case-control studies that reported large increases made no such adjustment, and the authors called them seriously flawed. Six cohort studies showed no significant increase. The other six reported raised mortality ratios without adjusting for smoking or alcohol, for example 1.91 among 17,800 insulation workers. The authors concluded that the evidence linking asbestos to laryngeal cancer was weak or non-existent. They added that some interactive effect between smoking and asbestos could not be totally excluded.

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: Review (critical analysis) of published epidemiologic studies: case-control studies, cohort or longitudinal studies, and a case series
• Who was studied: Published English-language studies on asbestos and laryngeal cancer: nine case-control studies, 12 cohort studies and one case series. The cohorts included Quebec chrysotile miners, South Carolina chrysotile textile workers, asbestos cement factory workers, British and North American insulation workers, South African crocidolite mining districts, US shipyard counties, Genoa shipyard workers, east London factory workers and North Italian chrysotile miners
• Exposure: Occupational asbestos exposure in the reviewed studies (chrysotile in mining, textile and cement work; crocidolite in South African mining districts; insulation, shipyard and asbestos factory work). The authors examined whether studies adjusted for cigarette smoking and alcohol (ethanol) consumption
• Main results:
  • Hinds et al case-control study: the unadjusted odds ratio for laryngeal cancer with asbestos exposure was 1.75, not statistically significant. After adjustment for cigarette and ethanol consumption it became one
  • Burch et al case-control study (Ontario, Canada): a subanalysis of 14 cases and 9 controls with definite asbestos exposure gave an odds ratio of 1.6, not statistically significant
  • Olsen and Sarbroe case-control study: a slightly increased odds ratio for asbestos exposure, with a 95% confidence limit of 1.0 to 3.4 after adjustment for tobacco and alcohol. The authors called the conclusion moot
  • Four case-control studies (Shettigara and Morgan; Stell and McGill) reported significant increases in the odds ratio, for example 13 in Morgan and Shettigara's follow-up study and about 15 in Stell and McGill's 119 patients. They did not adjust for smoking or alcohol, and the authors judged them seriously flawed
  • Six of the 12 cohort studies showed no significant increase in the standardized mortality ratio (SMR) for laryngeal cancer. The others reported raised SMRs without adjustment for smoking and alcohol
  • Selikoff et al cohort of 17,800 insulation workers in the United States and Canada: nine laryngeal cancer deaths, SMR 1.91, with no adjustment for smoking or ethanol. The authors' reanalysis of the older subgroup of 623 workers with 20 or more years since onset of work gave an SMR of 1.18
  • Rubino et al study of North Italian chrysotile miners: six laryngeal cancer deaths (SMR 3.16). All six were smokers, and the SMR was not adjusted for smoking
  • Quebec chrysotile miners (McDonald et al, 11,379 miners): no excess laryngeal cancer deaths. Laryngeal cancer SMR rose with smoking, from 0.46 in nonsmokers to 4.85 in heavy smokers
  • Libshitz et al case series: laryngeal cancer in three people with asbestosis, all of whom were cigarette smokers
• The authors' conclusion: The authors concluded that the evidence implicating asbestos in laryngeal cancer is weak or non-existent, and that the available epidemiologic evidence does not support a causal association
• Limitations the authors state:
  • The authors stated that it is impossible to exclude totally some interactive effects between smoking and asbestos in laryngeal cancer
  • The authors noted that dietary factors such as vitamin A intake have not been critically assessed in relation to laryngeal cancer in asbestos workers

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Laryngeal Cancer, Odds Ratio, standardized mortality ratio (SMR), Confounding.

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• Exposure to cement dust, related occupational groups and laryngeal cancer risk: results of a population based case-control study — A. Dietz, H. Ramroth, et al. (2004)
• A case-control study of occupational risk factors for laryngeal cancer — P. Wortley, T.L. Vaughan, et al. (1992)

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