Third mortality follow-up of the Mallinckrodt uranium processing workers, 1942–2019

Cato M. Milder, Sara C. Howard, Elizabeth D. Ellis, Ashley P. Golden, Sarah S. Cohen, Michael T. Mumma, Richard W. Leggett, Benjamin French, Lydia B. Zablotska, John D. Boice

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Introduction: Mallinckrodt Chemical Works was a uranium processing facility during the Manhattan Project from 1942 to 1966. Thousands of workers were exposed to low-dose-rates of ionizing radiation from external and internal sources. This third follow-up of 2514 White male employees updates cancer and noncancer mortality potentially associated with radiation and silica dust. Materials and methods: Individual, annualized organ doses were estimated from film badge records (n monitored = 2514), occupational chest x-rays (n = 2514), uranium urinalysis (n = 1868), radium intake through radon breath measurements (n = 487), and radon ambient measurements (n = 1356). Silica dust exposure from pitchblende processing was estimated (n = 1317). Vital status and cause of death determination through 2019 relied upon the National Death Index and Social Security Administration Epidemiological Vital Status Service. The analysis included standardized mortality ratios (SMRs), Cox proportional hazards, and Poisson regression models. Results: Vital status was confirmed for 99.4% of workers (84.0% deceased). For a dose weighting factor of 1 for intakes of uranium, radium, and radon decay products, the mean and median lung doses were 65.6 and 29.9 mGy, respectively. SMRs indicated a difference in health outcomes between salaried and hourly workers, and more brain cancer deaths than expected [SMR: 1.79; 95% confidence interval (CI): 1.14, 2.70]. No association was seen between radiation and lung cancer [hazard ratio (HR) at 100 mGy: 0.93; 95%CI: 0.78, 1.11]. The relationship between radiation and kidney cancer observed in the previous follow-up was maintained (HR at 100 mGy: 2.07; 95%CI: 1.12, 3.79). Cardiovascular disease (CVD) also increased significantly with heart dose (HR at 100 mGy: 1.11; 95%CI: 1.02, 1.21). Exposures to dust ≥23.6 mg/m3-year were associated with nonmalignant kidney disease (NMKD) (HR: 3.02; 95%CI: 1.12, 8.16) and kidney cancer combined with NMKD (HR: 2.46; 95%CI: 1.04, 5.81), though without evidence of a dose-response per 100 mg/m3-year. Conclusions: This third follow-up of Mallinckrodt uranium processors reinforced the results of the previous studies. There was an excess of brain cancers compared with the US population, although no radiation dose-response was detected. The association between radiation and kidney cancer remained, though potentially due to few cases at higher doses. The association between levels of silica dust ≥23.6 mg/m3-year and NMKD also remained. No association was observed between radiation and lung cancer. A positive dose-response was observed between radiation and CVD; however, this association may be confounded by smoking, which was unmeasured. Future work will pool these data with other uranium processing worker cohorts within the Million Person Study.

Original languageEnglish
Pages (from-to)161-175
Number of pages15
JournalInternational Journal of Radiation Biology
Volume100
Issue number2
DOIs
StatePublished - 2024

Funding

This work was supported in part by grants awarded to the National Council on Radiation Protection and Measurements from the U.S. Department of Energy [grant numbers DE-AU0000042 and DE-AU0000046]. Contract support was additionally received by Oak Ridge National Laboratory from the Office of Radiation and Indoor Air, U.S. Environmental Protection Agency through Interagency Agreement [DOE No. 1824 S581-A1], under contract number DE-AC05-00OR22725 with UT-Battelle. Contract support was also received by Oak Ridge Associated Universities from the U.S. Department of Energy through contract number DE-SC0014664. Dr. Zablotska’s work was funded by National Institute for Occupational Safety and Health and National Institutes of Health award [5R21OH011452] (Principal Investigator: L.B. Zablotska). The authors would like to recognize the contributions of everyone who has made this work possible through their consultation and participation in the Million Person Study. In particular, we would like to thank Dr. Loren Lipworth and Dr. Melinda Aldrich, who provided valuable insights on this paper as members of CMM’s dissertation committee, Mr. David Girardi, who helped considerably with data preparation, and Dr. Dale Preston, who took many hours out of his day to teach CMM the intricacies of Epicure.

FundersFunder number
National Institutes of Health5R21OH011452
U.S. Department of EnergyDE-AC05-00OR22725, DE-AU0000042, 1824 S581-A1, DE-AU0000046, DE-SC0014664
National Institute for Occupational Safety and Health
U.S. Environmental Protection Agency
Oak Ridge National Laboratory

    Keywords

    • Radiation
    • epidemiology
    • occupational exposures
    • uranium
    • uranium processing workers

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