Case-control study of lung cancer in Los Angeles county welders

Our plain-English summary of Case-control study of lung cancer in Los Angeles county welders, by C.J. Hull, E. Doyle, J.M. Peters, et al (American Journal of Industrial Medicine, 1989).

The study

• Authors: C.J. Hull, E. Doyle, J.M. Peters, D.H. Garabrant, L. Bernstein, S. Preston-Martin
• Journal: American Journal of Industrial Medicine
• Published: 1989;16(1):103-12
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000098).

Abstract

A case-control study of lung cancer in white male welders was undertaken to investigate possible environmental and occupational causes of a 50% excess of lung cancer observed in this occupational group. The subjects were identified from a population-based cancer registry in Los Angeles County. A standardized questionnaire was administered to either subjects or proxy informants of 90 lung cancer cases and 116 non-lung-cancer controls. Significantly increased risks of lung cancer were associated with tobacco smoking (odds ratio 7.6, p less than .005) and shipyard welding with at least a 10-year latency since first exposure (odds ratio 1.7, p less than .05). Although there were elevated risks associated with some specific welding processes, none were statistically significant. Control subjects were more likely to have had exposure to confined-space welding (odds ratio 0.6, 95% CI = 0.3-1.2), and this association was greatest where there had been at least a 20-year latency since first exposure (0.5, 95% CI = 0.3-1.0). We conclude that the excess of lung cancer in this welding population is contributed to by a higher frequency of smoking and probable exposure to asbestos in shipyards. Other factors may be important, but probably because of limited power and reliance on proxy information, this study failed to detect other statistically significant risks.

In plain English

This case-control study examined lung cancer in white male Los Angeles County welders, among whom the county cancer registry showed a 50% lung cancer excess by proportional incidence ratio. The authors compared welders with lung cancer to welders with other cancers, diagnosed 1972 to July 1987. Interviews, mostly with proxies, covered 90 cases and 116 controls. Three welders with mesothelioma were excluded. Ever having smoked was much more common among cases (odds ratio 7.6). The authors treated shipyard welding as the best available sign of asbestos exposure. This gave an odds ratio of 1.7 (95% CI 0.9 to 3.1), and 1.8 (95% CI 0.9 to 3.2, one-sided p 0.040) with at least 10 years since first shipyard work. Among the 85 deceased cases and 74 deceased controls used for specific exposures, interview-reported asbestos exposure (odds ratio 1.4, 95% CI 0.7 to 2.8) and welding processes and metals were not statistically significantly linked to lung cancer. The authors concluded that smoking and probable shipyard asbestos exposure contributed to the excess. They cited proxy reports, small numbers and limited power.

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: Case-control study using cancer controls (welders with cancers other than lung cancer), with telephone questionnaires to subjects or proxy informants
• Who was studied: White male welders aged 20 to 65 diagnosed with cancer in Los Angeles County from 1972 to July 1987, identified through the University of Southern California Cancer Surveillance Program registry. The registry had shown a 50% excess of lung cancer in these welders, based on a proportional incidence ratio. There were 128 eligible lung cancer cases and 177 controls aged 40 or older with other cancers. 90 cases and 116 controls were interviewed (participation 70% and 66%). Most interviews were with proxies of deceased subjects. Analysis of specific workplace exposures was limited to 85 deceased cases and 74 deceased controls. Analysis of shipyard employment used all 206 subjects. Three welders with mesothelioma were excluded.
• Exposure: Tobacco smoking, specific welding processes (manual metal-arc, gas-shielded), metals welded (stainless, high-alloy and mild steel), asbestos exposure as reported in interviews, fiberglass, confined-space welding, and shipyard welding employment. The authors used shipyard welding as the index of asbestos exposure. No asbestos fiber types were named.
• Main results:
  • Ever smoking versus never smoking: odds ratio 7.6, p = .001 for all subjects (88 of 90 cases and 98 of 116 controls had ever smoked), and odds ratio 5.1, p = .028 for deceased subjects.
  • Ever welded in a shipyard, all 206 subjects: odds ratio 1.7 (95% CI 0.9 to 3.1), with 37 cases and 34 controls exposed, one-sided p 0.053. With a 10-year latency: odds ratio 1.8 (95% CI 0.9 to 3.2), with 37 cases and 33 controls, one-sided p 0.040. The authors described this as becoming statistically significant with at least 10 years latency.
  • Asbestos exposure reported in interviews, deceased subjects only (85 cases, 74 controls): odds ratio 1.4 (95% CI 0.7 to 2.8), with 31 cases and 22 controls exposed. The elevation was not statistically significant.
  • Welding processes and metals showed no statistically significant associations in deceased subjects. Mild steel welding had an odds ratio of 1.6 (95% CI 0.8 to 3.1). The authors found no association of lung cancer with stainless or high-alloy steel welding.
  • Confined-space welding was more common among controls: odds ratio 0.6 (95% CI 0.3 to 1.2). The article's printed abstract gives 0.5 (95% CI 0.3 to 1.0) where there had been at least a 20-year latency.
• The authors' conclusion: The authors concluded that smoking and shipyard welding (probable asbestos exposure in shipyards) contributed to the excess lung cancer in these welders. They described the data on stainless or high-alloy steel welding as inconclusive.
• Limitations the authors state:
  • Proxy informants, small numbers and the use of other cancer patients as controls may have reduced the chance of finding true risks.
  • Proxy informants' answers about specific workplace exposures, including asbestos, may be inaccurate and must be interpreted cautiously.
  • The study had limited statistical power.
  • Stainless or high-alloy steel welding might be linked to some non-lung cancers in the controls, which would dilute differences between cases and controls.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Welders.

Medical terms in this study, explained in our Lexicon: Case-Control Study, Lung Cancer, Cancer Registry, Odds Ratio, Latency.

Related studies

• Occupational asbestos exposure and mesothelioma risk in Los Angeles County: application of an occupational hazard survey job-exposure matrix — C. Cicioni, S.J. London, et al. (1991)
• Incidence of cancer among welders, platers, machinists, and pipe fitters in shipyards and machine shops — S. Tola, P.L. Kalliomäki, et al. (1988)
• Polymorphism of glutathione S-transferase M1 and lung cancer risk among African-Americans and Caucasians in Los Angeles County, California — S.J. London, A.K. Daly, et al. (1995)
• Lung cancer risk in relation to the CYP2E1 Rsa I genetic polymorphism among African-Americans and Caucasians in Los Angeles County — S.J. London, A.K. Daly, et al. (1996)
• Retention of asbestos bodies in the lungs of welders — J.C. Pairon, L. Martinon, et al. (1994)
• Cancer incidence among mild steel and stainless steel welders and other metal workers — K.S. Hansen, J.M. Lauritsen, et al. (1996)

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