Evidence of confounding by smoking of associations between radiation and lung cancer mortality among workers at the Savannah River Site.
Am J Ind Med 2011 Jun; 54(6):421-427
Background: This study investigates confounding by cigarette smoking of associations between occupational exposure to ionizing radiation and lung cancer mortality among workers at the Savannah River Site (SRS). Methods: Thirteen thousand two hundred sixty-five white males hired at SRS between 1950 and 1986 were followed through 2002 to ascertain causes of death. Estimates of radiation doses from external sources and internal tritium uptakes were derived from dosimetry records. Logistic regression methods were used to derive discrete-time estimates of rate ratios. An indirect approach to control for unmeasured confounding by smoking was employed that involves joint modeling of lung cancer and chronic obstructive pulmonary disease (COPD) mortality. Results: Prior to indirect adjustment for smoking, there was minimal evidence of association between lung cancer mortality and cumulative radiation dose under a 10-year lag assumption (RR at 100 mSv=0.90; 90% CI: 0.80-1.01). Subsequent to indirect adjustment for smoking, the association between lung cancer mortality and cumulative radiation dose under a 10-year lag was positive (RR at 100 mSv = 1.33; 90% CI: 1.01-1.77). Conclusions: In this cohort, there is evidence of negative confounding of radiation dose-lung cancer mortality associations by cigarette smoking.
Biohazards; Biological-effects; Biological-monitoring; Biological-systems; Biostatistics; Cancer-rates; Epidemiology; Exposure-assessment; Exposure-methods; Health-surveys; Ionizing-radiation; Mathematical-models; Medical-monitoring; Mortality-data; Mortality-rates; Mortality-surveys; Occupational-diseases; Occupational-exposure; Occupational-hazards; Occupational-health; Physical-reactions; Physiological-effects; Physiological-factors; Physiological-measurements; Physiological-response; Pulmonary-disorders; Pulmonary-system-disorders; Quantitative-analysis; Radiation-effects; Radiation-exposure; Radiation-levels; Radiation-measurement; Risk-analysis; Risk-factors; Smoking; Statistical-analysis; Work-areas; Work-environment; Worker-health; Work-operations;
Author Keywords: bias (epidemiology); lung neoplasms/epidemiology/etiology; occupational exposure/adverse effects; smoking/adverse effects; ionizing radiation
David B. Richardson, Department of Epidemiology, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
Research Tools and Approaches: Cancer Research Methods
American Journal of Industrial Medicine
University of North Carolina at Chapel Hill, Chapel Hill, North Carolina