Objective: To study the possible association between iron oxide exposures and lung cancer risk among workers employed in a French steel-producing factory.
Methods: A historical cohort was set up of all workers ever employed for at least one year between 1959 and 1997. The cohort was followed up for mortality from January 1968 to December 1998. Causes of death were ascertained from death certificates. Job histories and smoking habits were available for 99.7% and 72.3% respectively. Occupational exposures were assessed by a factory-specific job-exposure matrix (JEM) developed by a panel of 8 experts and validated with atmospheric measurements. Standardized Mortality Ratios (SMRs) were computed using local death rates (external references). Poisson regressions were used to estimate the Relative Risks (RRs) for occupational exposures (internal references), adjusted on potential confounding factors.
Results: The cohort comprised 16,742 males and 959 females. Among males, the observed mortality was lower than expected for all causes (2,338 deaths, SMR 0.81, 0.78-0.85) and for lung cancer (233 deaths, SMR 0.89, 0.78-1.01). No lung cancer excess was observed for exposure to iron oxides (RR 0.80, 0.55-1.17) and we found no dose-response relationship with intensity, duration of exposure, and cumulative indices. Unadjusted RRs were above unity for asbestos (RR 1.14, 0.89-1.48), silica (RR 1.17, 0.76-1.80), and polycyclic aromatic hydrocarbons (RR 1.05, 0.61-1.80) compared with the non-exposed groups, and no dose-response relationship was observed with intensity, duration of exposure, and cumulative indices. A significant bladder cancer excess was observed among workers exposed to oil mist (RR 2.44, 1.06-5.60), increasing significantly with intensity, duration of exposure, and cumulative indices.
Conclusion: This study did not detect any relationship between exposure to iron oxides and lung cancer mortality. An excess of mortality from bladder cancer was found among workers exposed to oil mist.
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