| The study was a nested case-control study of the association between lung cancer mortality and cumulative internal lung doses among a cohort of workers employed at the Rocky Flats Plant in Colorado from 1951 to 1989. Lung cancer risk was elevated among workers with cumulative internal lung doses of more than 400 mSv. The dose-response relation was not consistent at high doses. Restricting the analysis to workers employed 15 to 25 years showed a statistically significant linear trend with dose, suggesting a strong healthy worker survivor effect. No associations were found between lung cancer mortality and cumulative external penetrating radiation dose or cumulative exposures to asbestos, beryllium, hexavalent chromium, or nickel. |
| Cases and controls were selected from a preliminary database of 22,883 workers who were employed at the Rocky Flats Plant between January 1, 1952, and July 10, 1996. Vital status was determined through December 31, 1996, by submitting personally identifying information to the Social Security Administration and Pension Benefits, Inc., a commercial provider of vital status information. A final cohort roster was developed for 16,248 production-era workers who were employed for 6 months or more between 1952 and 1989. Incidence density sampling was used to select controls from the set of subjects at risk at the time of death of each case. Four controls were randomly selected from each risk set for comparison with each lung cancer case. |
| The Rocky Flats Plant produced nuclear weapons components from 1952 to 1989. Workers were exposed to several plutonium isotopes, americium 241, and uranium. Uranium was used in the construction of some weapons components in the 1960s and americium 241 was used for weapons and other uses. Internal exposures to the radionuclides occurred primarily by acute inhalation of radioactive particles accidentally released into the workplace atmosphere. Data from a job exposure matrix were used to estimate annual exposures to asbestos (fibers/cc), beryllium (µg/m3), hexavalent chromium (ppm), and nickel (µg/m3), expressed as the product of time worked and the estimated time-weighted average daily breathing zone concentrations that were usually experienced by workers. Exposures to plutonium isotopes were routinely quantified with estimates of systemic deposition. Data for external radiation doses came from electronic databases of recorded doses from film and thermoluminescent personal dosimeters that measured total body doses from external gamma photon and neutron exposures. The dosimeters recorded doses for individual workers for periods ranging from quarter years to years. Unadjusted neutron doses are reported in millirad, and unadjusted gamma exposures are in millirem. The total unadjusted penetrating dose (neutrons + gamma) is reported in millirem Histories of smoking frequency for cases and controls were obtained by telephone interviews with surrogate interviewees, regardless of the vital status of the subject, in an effort to provide reliable historical data and to reduce potential bias from self-reporting. |
