Carcinoma of the pharynx and tonsils in an occupational cohort of asphalt workers

Our plain-English summary of Carcinoma of the pharynx and tonsils in an occupational cohort of asphalt workers, by F. Zanardi, R. Salvarani, R.M. Cooke, et al (Epidemiology, 2013).

The study

• Authors: F. Zanardi, R. Salvarani, R.M. Cooke, R. Pirastu, M. Baccini, D. Christiani, S. Curti, A. Risi, A. Barbieri, G. Barbieri, S. Mattioli, F.S. Violante
• Journal: Epidemiology
• Published: 2013;24(1):100-3
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: We investigated a possible association between pharyngeal/tonsillar carcinoma and mixed carcinogen exposures in an asphalt roll company in Italy that used asbestos until 1979, when a new factory was built using a different production process.

Methods: We evaluated all workers involved in the entire production history of the company, divided into two subcohorts based on exposure status (workers in the original factory, 1964-1979, and those who worked only in the new factory, 1980-1997). We ascertained the vital status of the study population in February 2001.

Results: Among the subset of workers in the earlier subcohort, there were five deaths from pharyngeal/tonsillar carcinoma for a standardized mortality ratio of 21 (95% confidence interval = 8.8-51). No cases were recorded among workers hired after 1979.

Conclusion: The increased standardized mortality ratio for this relatively rare cancer among workers exposed before 1979 may have been due to carcinogenic exposures at the plant.

In plain English

This cohort study included all 415 workers of an asphalt roofing-roll company in Emilia-Romagna, Italy, from 1964 to its 1997 closure, with vital status checked in February 2001. The original factory used asbestos. After a 1979 fire, management agreed to eliminate asbestos and a new factory opened. The authors compared 295 workers who started in the old factory with 120 who worked only in the new one. Five workers died of carcinoma of the pharynx/tonsils. All were old-factory production-line workers exposed to chrysotile asbestos, bitumen fumes, solvents, polycyclic aromatic hydrocarbons and other dusts. For the 104 old-factory blue-collar workers exposed to the production sector, including subcontracted warehouse workers, the standardized mortality ratio (SMR) for lip, oral cavity and pharynx cancer was 21 (95% CI 8.8 to 51) versus regional rates. No such cases occurred among new-factory workers. Old-factory workers had a gastric cancer SMR of 3.0 (95% CI 1.3 to 7.3) and a lung cancer SMR of 1.0 (0.4 to 2.4). The authors concluded the events may not have been due to chance, though the responsible exposures were unclear. They lacked dose information and could not separate work from individual factors.

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: Retrospective occupational cohort mortality study (standardized mortality ratios against regional rates), published as a brief report
• Who was studied: 415 workers (343 men, 72 women), including 52 subcontracted warehouse workers, at an asphalt roll company in the Emilia-Romagna region of Italy, employed during the plant's production history from 1964 to 1997. 295 started in the old factory (January 1964 to June 1979) and 120 worked only in the new factory. Vital status was ascertained on 7 February 2001.
• Exposure: Work in the original asphalt roll factory, which used asbestos, compared with work only in the new factory built after a 1979 fire, from which asbestos was eliminated
• Main results:
  • Vital status of the cohort was ascertained on 7 February 2001, four years after the plant closed in 1997
  • Five deaths from carcinoma of the pharynx/tonsils occurred, all among production-line workers in the old factory. These workers had coexposure to chrysotile asbestos fibers, bitumen fumes, solvents, PAH and other dusts.
  • For old-factory workers exposed to the production sector where asbestos was used, the SMR for carcinoma of the lip, oral cavity and pharynx was 21 (95% CI 8.8 to 51). Table 3 gives 21.1 (8.8 to 50.7), based on 5 observed versus 0.2 expected. Table 1 shows this group had 104 workers: 67 production-line workers and 37 subcontracted warehouse workers.
  • No cases of cancer of the pharynx or oral cavity occurred among workers exposed only to the new factory
  • The old-factory subcohort as a whole had a stomach cancer SMR of 3.0 (95% CI 1.3 to 7.3), based on 5 observed versus 1.6 expected
  • The old-factory subcohort as a whole had a lung (trachea, bronchus and lung) cancer SMR of 1.0 (95% CI 0.4 to 2.4), based on 5 observed versus 5.0 expected. The authors reported no evidence of increased mortality from lung cancer or cardiovascular diseases.
  • Forty deaths were recorded over 9948 person-years of follow-up in the whole cohort
  • The five pharyngeal/tonsillar cancer cases had a relatively young age of onset
• The authors' conclusion: The authors concluded that the size of the SMR for this rare cancer suggests the cases may not have been due to chance, although it is unclear which of the mixed carcinogen exposures were involved
• Limitations the authors state:
  • Limited exposure information did not allow dose-response analysis
  • Few person-years and relatively short follow-up prevented assessment of long-latency tumors such as mesothelioma
  • The authors could not separate the contribution of work exposures from individual factors

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: Carcinoma, standardized mortality ratio (SMR), confidence interval, Carcinogenic.

Related studies

• Occupational exposures to asbestos, polycyclic aromatic hydrocarbons and solvents, and cancers of the oral cavity and pharynx: a quantitative literature review — S. Paget-Bailly, D. Cyr, et al. (2012)
• A case-control study of lung cancer nested in a cohort of European asphalt workers — A. Olsson, H. Kromhout, et al. (2010)
• Occupational exposures and squamous cell carcinoma of the oral cavity, pharynx, larynx, and oesophagus: a case-control study in Sweden — P. Gustavsson, R. Jakobsson, et al. (1998)
• Oral and pharyngeal cancer risk associated with occupational carcinogenic substances: Systematic review — K.H. Awan, R. Hegde, et al. (2018)
• Estimating exposures in the asphalt industry for an international epidemiological cohort study of cancer risk — I. Burstyn, P. Boffetta, et al. (2003)
• Occupational asbestos exposure is associated with pharyngeal squamous cell carcinoma in men from the greater Boston area — S.M. Langevin, M.H. O'Sullivan, et al. (2013)

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