Risk of lung cancer in workers producing stainless steel and metallic alloys

Our plain-English summary of Risk of lung cancer in workers producing stainless steel and metallic alloys, by J.J. Moulin, T. Clavel, D. Roy, et al (International Archives of Occupational and Environmental Health, 2000).

The study

• Authors: J.J. Moulin, T. Clavel, D. Roy, B. Dananché, N. Marquis, J. Févotte, J.M. Fontana
• Journal: International Archives of Occupational and Environmental Health
• Published: 2000;73(3):171-80
• Cited by: 51 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: The mortality of workers involved in the production of stainless and alloyed steel from 1968 to 1992 was studied, in order to investigate the risk of lung cancer due to exposure to metals, i.e. iron oxides, chromium and/or nickel compounds.

Methods: The study design was a historical cohort mortality study and a nested case-control study concerning lung cancer. Standardized mortality ratios (SMRs) were computed using regional mortality rates as an external reference for comparing observed and expected numbers of deaths, adjusting for age, sex and calendar time. Conditional logistic regression was used to estimate odds ratios (ORs). Occupational exposure was assessed through the complete job histories of cases and controls and a specific job-exposure matrix.

Results: The cohort comprised 4,288 male and 609 female workers. The observed overall mortality was significantly lower than expected [649 deaths; SMR = 0.91; 95% confidence interval (CI) 0.84-0.98]. No significant SMR was observed for mortality from lung cancer (54 deaths; SMR = 1.19; CI 0.88-1.55). The case-control study was based on 54 cases and 162 individually matched controls. Smoking habits were available for 71%. No lung cancer excess was observed for exposure to (1) metals and/or their compounds, i.e. iron (OR = 0.94, CI 0.48-1.86), chromium and/or nickel (OR = 1.18, CI 0.62-2.25), and cobalt (OR =0.64, CI 0.33-1.25), (2) acid mists (OR = 0.43, CI 0.17-1.10), and (3) asbestos (OR = 1.00, CI 0.54-1.86). With respect to exposure to polycyclic aromatic hydrocarbons (PAHs) and silica, which are often found together in workplaces, (1) high and statistically significant lung cancer excesses were observed, the ORs being 1.95 (CI 1.03-3.72) and 2.47 (CI 1.28-4.77) respectively, (2) quantitative exposure parameters revealed upward trends reaching statistical significance (P < 0.05), and (3) adjustments for tobacco consumption did not reveal any confounding factors from smoking.

Conclusion: This study failed to detect any relationship between lung cancer and exposure to iron, chromium, nickel and/or their compounds. High and statistically significant relative risks, along with increasing trends, were observed for simultaneous exposure to PAHs and silica.

In plain English

This study followed 4,897 workers (4,288 men and 609 women) employed for at least 1 year between 1968 and 1991 at a French factory producing stainless and alloyed steel, with deaths tracked to the end of 1992. Lung cancer deaths (54) were slightly more frequent than expected from regional death rates (SMR 1.19), but the difference was not statistically significant. In a nested case-control study of these 54 cases and 162 matched controls, a panel of experts estimated each job's exposure to metals, acid mists, polycyclic aromatic hydrocarbons (PAHs), silica and asbestos. Workers exposed to asbestos showed no excess of lung cancer (odds ratio 1.00, 95% CI 0.54 to 1.86). The authors concluded the study failed to detect any relationship between lung cancer and iron, chromium, nickel or their compounds. PAH exposure (OR 1.95) and silica exposure (OR 2.47) were linked to significantly raised risk, and smoking did not explain this. Because the two exposures occurred together, the authors could not separate their effects. The authors said that, with only 54 cases, the study had too little statistical power to detect a small asbestos risk, and that missing historical measurements probably led to misclassified asbestos exposure.

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: Historical cohort mortality study of one factory, followed by a nested case-control study of lung cancer that used an expert-built job-exposure matrix
• Who was studied: 4,897 workers (4,288 men, 609 women) employed for at least 1 year between 1 January 1968 and 31 December 1991 in a French factory producing stainless and alloyed steel. Follow-up for deaths ran to 31 December 1992 and totalled 87,247 person-years.
• Exposure: Semi-quantitative expert estimates, made without airborne measurements, of exposure to iron, chromium and/or nickel (assessed together), cobalt, acid mists, PAHs, silica and asbestos. The authors suggested asbestos in a steel factory was present only as an insulation material.
• Main results:
  • Lung cancer mortality in the whole cohort was slightly raised but not statistically significant: 54 observed deaths against 45.37 expected, SMR 1.19. Table 2 gives a 95% CI of 0.89 to 1.55 for both sexes; the abstract gives 0.88 to 1.55.
  • Among men, 2 deaths from cancer of the pleura were observed against 1.52 expected (SMR 1.32, 95% CI 0.16 to 4.75).
  • The case-control study included 54 lung cancer cases and 162 matched controls. Smoking information was available for 66.7% of cases and 72.8% of controls.
  • Asbestos exposure: 29 exposed cases and 87 exposed controls. The crude odds ratio was 1.00 (95% CI 0.54 to 1.86). After adjustment for PAHs and silica it was 0.55 (95% CI 0.25 to 1.22), not statistically significant.
  • After adjustment for smoking, PAH and silica exposure, the odds ratios for all five other agents (chromium and/or nickel, iron, cobalt, acid mists, asbestos) were below 1, and none was statistically significant.
  • PAH exposure (25 exposed cases, 50 exposed controls) had a statistically significant crude odds ratio of 1.95 (95% CI 1.03 to 3.72).
  • Silica exposure (26 exposed cases, 45 exposed controls) had a statistically significant crude odds ratio of 2.47 (95% CI 1.28 to 4.77).
  • Trends in lung cancer risk with increasing PAH and silica exposure did not change when smoking was taken into account.
  • No link was found for chromium and/or nickel. The crude odds ratio was 1.18 (95% CI 0.62 to 2.25), and the odds ratio adjusted for PAHs, silica and smoking was 0.67.
  • Smoking was a strong risk factor: current smokers versus never smokers had an odds ratio of 17.0 (95% CI 2.23 to 130).
• The authors' conclusion: The authors concluded the study failed to detect any relationship between lung cancer and exposure to iron, chromium, nickel and/or their compounds. They observed high, statistically significant relative risks with increasing trends for simultaneous exposure to PAHs and silica, not confounded by smoking. They found no excess in workers exposed to asbestos. For cobalt, the relative risk was below 1, with significant negative trends with cumulative exposure.
• Limitations the authors state:
  • With only 54 cases, the study's statistical power was too low to detect a lung cancer risk from asbestos that might be close to 1 at the lower exposure levels of a steel factory.
  • There were no historical measurements, which probably led to misclassification of asbestos exposure.
  • Non-differential misclassification in the expert exposure estimates may partly explain odds ratios close to 1.
  • PAH and silica exposures were strongly correlated, so the authors could not tell whether the risk came from one agent or from simultaneous exposure.
  • Smoking habits were known for only 71% of the study population.
  • The experts could not separate chromium exposure from nickel exposure.
  • Including workers already active on 1 January 1968 may have introduced survivor selection, though the authors considered this bias likely to be limited.

Topics

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

Medical terms in this study, explained in our Lexicon: Lung Cancer, nested case-control study, standardized mortality ratio (SMR), Odds Ratio, Occupational Exposure, confidence interval, Case-Control Study, Habit.

Related studies

• Cancer incidence among mild steel and stainless steel welders and other metal workers — K.S. Hansen, J.M. Lauritsen, et al. (1996)
• Cancer risks among iron and steel workers in Anshan, China, Part I: Proportional mortality ratio analysis — Z. Xu, G.W. Pan, et al. (1996)
• Lung and bladder cancer in a Norwegian municipality with iron and steel producing industry: population based case-control studies — T.K. Grimsrud, H. Langseth, et al. (1998)
• Exposure to stainless steel welding fumes and lung cancer: a meta-analysis — B. Sjögren, K.S. Hansen, et al. (1994)
• Asbestos-related disease in employees of a steel mill and a glass bottle-manufacturing plant — R.S. Kronenberg, J.L. Levin, et al. (1991)
• A historical prospective study of European stainless steel, mild steel, and shipyard welders — L. Simonato, A.C. Fletcher, et al. (1991)

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