Saf Health Work.  2017 Sep;8(3):258-266. 10.1016/j.shaw.2016.12.001.

Cancer Risks among Welders and Occasional Welders in a National Population-Based Cohort Study: Canadian Census Health and Environmental Cohort

Affiliations
  • 1Occupational Cancer Research Centre, Prevention and Cancer Control, Cancer Care Ontario, Toronto, Ontario, Canada. jill.macleod@occupationalcancer.ca
  • 2School of Occupational and Public Health, Ryerson University, Toronto, Ontario, Canada.
  • 3Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
  • 4Health Analysis Division, Statistics Canada, Ottawa, Ontario, Canada.
  • 5Departments of Sociology and Economics, University of New Brunswick Fredericton Campus, Fredericton, New Brunswick, Canada.
  • 6CAREX Canada, Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.

Abstract

BACKGROUND
Welders are exposed to many known and suspected carcinogens. An excess lung cancer risk among welders is well established, but whether this is attributable to welding fumes is unclear. Excess risks of other cancers have been suggested, but not established. We investigated welding cancer risks in the population-based Canadian Census Health and Environmental Cohort.
METHODS
Among 1.1 million male workers, 12,845 welders were identified using Standard Occupational Classification codes and followed through retrospective linkage of 1991 Canadian Long Form Census and Canadian Cancer Registry (1992–2010) records. Hazard ratios (HRs) were calculated using Cox proportional hazards models based on estimated risks of lung cancer, mesothelioma, and nasal, brain, stomach, kidney, and bladder cancers, and ocular melanoma. Lung cancer histological subtypes and risks by industry group and for occasional welders were examined. Some analyses restricted comparisons to blue-collar workers to minimize effects of potential confounders.
RESULTS
Among welders, elevated risks were observed for lung cancer [HR: 1.16, 95% confidence interval (CI): 1.03–1.31], mesothelioma (HR: 1.78, 95% CI: 1.01–3.18), bladder cancer (HR: 1.40, 95% CI: 1.15–1.70), and kidney cancer (HR: 1.30, 95% CI: 1.01–1.67). When restricted to blue-collar workers, lung cancer and mesothelioma risks were attenuated, while bladder and kidney cancer risks increased.
CONCLUSION
Excess risks of lung cancer and mesothelioma may be partly attributable to factors including smoking and asbestos. Welding-specific exposures may increase bladder and kidney cancer risks, and particular sources of exposure should be investigated. Studies that are able to disentangle welding effects from smoking and asbestos exposure are needed.

Keyword

Keywords; cohort studies; neoplasms; occupational diseases; occupational exposure; welding
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