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Welding fumes and lung cancer: a meta-analysis of case-control and cohort studies
  1. Manoj Kumar Honaryar1,2,3,
  2. Ruth M Lunn4,
  3. Danièle Luce5,
  4. Wolfgang Ahrens6,
  5. Andrea ’t Mannetje7,
  6. Johnni Hansen8,
  7. Liacine Bouaoun1,
  8. Dana Loomis1,9,
  9. Graham Byrnes1,
  10. Nadia Vilahur1,10,
  11. Leslie Stayner11,
  12. Neela Guha1,12
  1. 1International Agency for Research on Cancer, Lyon, France
  2. 2Service de médcine et addictologie, Centre Hospitalier des Quatre Villes (CH4V), Saint-Cloud et Sèvres, France
  3. 3Ecole des hautes études en santé publique (EHESP), Paris, France
  4. 4National Institute of Environmental Health Sciences, Durham, North Carolina, USA
  5. 5Univ Rennes, Inserm, EHESP, Irset (Institut de recherche en santé, environnement et travail) - UMR_S 1085, Pointe-à-Pitre, France
  6. 6Leibniz Institute for Prevention Research and Epidemiology - BIPS, Bremen, Germany
  7. 7Centre for Public Health Research, Massey University, Wellington, New Zealand
  8. 8Danish Cancer Society Research Center, København, Denmark
  9. 9University of Nevada, Reno, Reno, Nevada, USA
  10. 10European Commission, Italy
  11. 11Division of Epidemiology and Biostatistics, University of Illinois, School of Public Health, Chicago, Illinois, USA
  12. 12Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, California, USA
  1. Correspondence to Dr Neela Guha, California Environmental Protection Agency; neela{at}


Background An estimated 110 million workers are exposed to welding fumes worldwide. Welding fumes are classified by the International Agency for Research on Cancer as carcinogenic to humans (group 1), based on sufficient evidence of lung cancer from epidemiological studies.

Objective To conduct a meta-analysis of case-control and cohort studies on welding or exposure to welding fumes and risk of lung cancer, accounting for confounding by exposure to asbestos and tobacco smoking.

Methods The literature was searched comprehensively in PubMed, reference lists of relevant publications and additional databases. Overlapping populations were removed. Meta-relative risks (mRRs) were calculated using random effects models. Publication bias was assessed using funnel plot, Eggers’s test and Begg’s test.

Results Forty-five studies met the inclusion criteria (20 case-control, 25 cohort/nested case-control), which reduced to 37 when overlapping study populations were removed. For ‘ever’ compared with ‘never’ being a welder or exposed to welding fumes, mRRs and 95% CIs were 1.29 (1.20 to 1.39; I2=26.4%; 22 studies) for cohort studies, 1.87 (1.53 to 2.29; I2=44.1%; 15 studies) for case-control studies and 1.17 (1.04 to 1.38; I2=41.2%) for 8 case-control studies that adjusted for smoking and asbestos exposure. The mRRs were 1.32 (95% CI 1.20 to 1.45; I2=6.3%; 15 studies) among ‘shipyard welders’, 1.44 (95% CI 1.07 to 1.95; I2=35.8%; 3 studies) for ‘mild steel welders’ and 1.38 (95% CI 0.89 to 2.13; I2=68.1%; 5 studies) among ‘stainless steel welders’. Increased risks persisted regardless of time period, geographic location, study design, occupational setting, exposure assessment method and histological subtype.

Conclusions These results support the conclusion that exposure to welding fumes increases the risk of lung cancer, regardless of the type of steel welded, the welding method (arc vs gas welding) and independent of exposure to asbestos or tobacco smoking.

  • meta-analysis
  • meta-regression
  • lung cancer
  • welding
  • welding fumes
  • mild steel welding
  • stainless steel welding
  • arc welding
  • gas welding
  • exposure-effect analysis

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  • Contributors NG designed the analysis plan in collaboration with all other coauthors. MKH, RL, DL, WA extracted data from original manuscripts. MKH, LB, GB conducted the data analysis. All authors made substantial contributions to the conception or design of the work; or the acquisition, analysis or interpretation of data for the work; AND drafting the work or revising it critically for important intellectual content; AND final approval of the version to be published; AND agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Patient consent for publication Not required.