Oral and pharyngeal cancer risk associated with occupational carcinogenic substances: systematic review

Background: Oral and pharyngeal cancers (OPC) represent the seventh most common type of cancer and the seventh leading cause of deaths by cancer worldwide. Few studies have assessed the occupational exposure risks associated with OPC and in many cases the results are conflicting. The aim of this study was to determine, through a systematic review, the association of OPC and exposure to different occupational carcinogenic substances. Methods: The addressed focused question was 'Is there an association of occupational carcinogenic substances with OPC?' PubMed, MEDLINE, EMBASE, and ISI Web of Science databases were searched between January 1995 up to and including July 2016 using the keywords 'oral cancer,' 'pharyngeal cancer,' 'pharyngeal neoplasms,' 'oral neoplasms,' 'occupational disease,' 'occupational exposure,' and 'occupational risk factor' in various combinations. Letters to the Editor, review articles, case reports, and unpublished articles were excluded. Results: Fourteen original articles were included. Majority of the studies were conducted in European countries and used a case-control design. The results showed a significant association between formaldehyde, wood dust, coal dust, asbestos, welding fumes, and risk of developing OPC, while marginal association was observed with metal and leather dust. No associated risk was observed for textile fibers. Conclusion: There is some evidence to suggest associations of occupational substances with OPC, particularly in the pharynx. Future well-designed studies are required to confirm or rule out with confidence the associated exposure risk of these substances.