Workplace exposures and oesophageal cancer

Our plain-English summary of Workplace exposures and oesophageal cancer, by M.E. Parent, J. Siemiatycki, L. Fritschi (Occupational and Environmental Medicine, 2000).

The study

• Authors: M.E. Parent, J. Siemiatycki, L. Fritschi
• Journal: Occupational and Environmental Medicine
• Published: 2000;57(5):325-34
• Cited by: 33 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: To describe the relation between oesophageal cancer and many occupational circumstances with data from a population based case-control study.

Methods: Cases were 99 histologically confirmed incident cases of cancer of the oesophagus, 63 of which were squamous cell carcinomas. Various control groups were available; for the present analysis a group was used that comprised 533 population controls and 533 patients with other types of cancer. Detailed job histories were elicited from all subjects and were translated by a team of chemists and hygienists for evidence of exposure to 294 occupational agents. Based on preliminary results and a review of literature, a set of 35 occupational agents and 19 occupations and industry titles were selected for this analysis. Logistic regression analyses were adjusted for age, birthplace, education, respondent (self or proxy), smoking, alcohol, and beta-carotene intake.

Results: Sulphuric acid and carbon black showed the strongest evidence of an association with oesophageal cancer, particularly squamous cell carcinoma. Other substances showed excess risks, but the evidence was more equivocal-namely chrysotile asbestos, alumina, mineral spirits, toluene, synthetic adhesives, other paints and varnishes, iron compounds, and mild steel dust. There was considerable overlap in occupational exposure patterns and results for some of these substances may be mutually confounded. None of the occupations or industry titles showed a clear excess risk; the strongest hints were for warehouse workers, food services workers, and workers from the miscellaneous food industry.

Conclusions: The data provide some support for an association between oesophageal cancer and a handful of occupational exposures, particularly sulphuric acid and carbon black. Many of the associations found have never been examined before and warrant further investigation.

In plain English

This population-based case-control study examined workplace exposures and oesophageal cancer in Montreal-area men aged 35 to 70 whose cancers were diagnosed between 1979 and 1985. It compared 99 men with oesophageal cancer (63 with squamous cell carcinoma) with 1,066 controls: 533 men from the general population and 533 men with other cancers. Chemists and industrial hygienists translated each man's job history into likely exposures. The authors analysed 35 substances, including chrysotile asbestos, adjusting for smoking, alcohol, beta-carotene intake and other factors. For any exposure to chrysotile asbestos, the odds ratio was 1.4 (95% CI 0.8 to 2.4) for all oesophageal cancers and 2.0 (1.1 to 3.8) for squamous cell carcinoma. Too few men had substantial exposure to judge whether risk rose with dose. When other workplace substances were added to the model, the squamous cell figure was 1.7 (0.8 to 3.6). Carbon black and sulphuric acid showed the strongest associations. The authors described the evidence for chrysotile asbestos as more equivocal. They noted that overlapping exposures may confound one another.

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: Population-based case-control study (hypothesis-generating), analysed with unconditional logistic regression adjusted for age, respondent type, birthplace, education, beer and spirits drinking, cigarette-years, smoking pattern and a beta-carotene index
• Who was studied: Men aged 35 to 70 living in the Montreal area with newly diagnosed, histologically confirmed cancer, 1979 to 1985. There were 99 oesophageal cancer cases: 63 squamous cell carcinoma, 23 adenocarcinoma and 13 of uncertain type. The main analysis used 1,066 pooled controls: 533 population controls plus 533 men chosen at random from patients with other cancers.
• Exposure: A team of chemists and industrial hygienists coded each subject's job history for exposure to 294 substances, without knowing who had cancer. This analysis covered 35 substances, including chrysotile asbestos, grouped as unexposed, any exposure, or substantial exposure. Chrysotile asbestos exposure was coded most often in motor vehicle mechanics, welders and flame cutters, and stationary engineers. The authors also analysed 19 occupations and industries.
• Main results:
  • Chrysotile asbestos, any exposure: OR 1.4 (95% CI 0.8 to 2.4) for all oesophageal cancers (21 exposed cases), and OR 2.0 (1.1 to 3.8) for squamous cell carcinoma (17 exposed cases). The authors described this as a significant twofold increase for squamous cell carcinoma.
  • Only 2 cases (all types) and 1 squamous cell case had substantial chrysotile asbestos exposure: OR 1.3 (0.3 to 6.2) and OR 1.1 (0.1 to 9.7). The authors said there were too few such subjects to comment on a dose-response trend.
  • In a model that also included carbon black, sulphuric acid, toluene, other paints and varnishes, and iron compounds, chrysotile asbestos gave OR 1.4 (0.7 to 2.7) for all oesophageal cancers (18 exposed cases) and OR 1.7 (0.8 to 3.6) for squamous cell carcinoma (14 exposed cases).
  • Carbon black, any exposure: OR 2.1 for all oesophageal cancers and OR 3.4 for squamous cell carcinoma, with evidence of a dose-response pattern. Sulphuric acid, any exposure: OR 2.2 (1.2 to 4.3) for all types.
  • No occupation or industry showed a clear pattern of excess risk. The strongest indications were for warehouse workers, food services workers and the miscellaneous food industry.
• The authors' conclusion: The authors concluded that the data suggest an excess risk of oesophageal cancer, particularly squamous cell carcinoma, with carbon black and sulphuric acid. They judged the evidence for chrysotile asbestos and several other substances more equivocal, and said many of the associations warrant further investigation.
• Limitations the authors state:
  • Exposures overlapped, so an apparent risk from one substance may reflect another substance in the study, or one that was not assessed.
  • The total number of cases was limited.
  • For occupations and industries, numbers were small and statistical power was low.
  • Some residual confounding by alcohol and smoking may remain.
  • Exposure was assessed after the fact, from indirect and imperfect information sources.

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: Esophageal Cancer, Case-Control Study, Squamous Cell Carcinoma, Chrysotile, Occupational Exposure.

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