Asbestos exposure and laryngeal cancer

Objective: To carry out a systematic review of the evidence relating asbestos exposure to the risk of laryngeal cancer. Method: All identified studies of asbestos workers providing data on laryngeal disease were reviewed, together with studies of laryngeal cancers giving epidemiological or experimental evidence of associated exposures. Results: Confounding due to smoking and alcohol intake, and to a lesser extent diet and socio-economic factors, creates a major difficulty over the identification of any asbestos or other occupational effect. Not only are smoking and alcohol independently associated with large increases in relative risk (RR) of laryngeal cancer, but also have a synergistic effect with each other. Few of the studies provide details of either habit. Among 24 prospective studies for which a standardized mortality ratio (SMR) was available, nine had an SMR at or below unity, and among a further 11 without an SMR for comparison, in only one was there a clear excess risk. In 17 retrospective studies, only two showed a significantly increased RR. Evidence from animal experiments, studies of associations with pleural plaques, and autopsy findings also appear negative or inconclusive. Conclusion: The evidence does not indicate that asbestos exposure increases the RR of laryngeal cancer.