Int J Radiat Biol. 2021 May 10:1-33. doi: 10.1080/09553002.2021.1917786. Online ahead of print.
ABSTRACT
PURPOSE: Risks of occupational radiation exposures of workers involved in uranium refining and processing (“uranium processing workers“) may be different from risks of other workers from the nuclear fuel cycle. Pooling of individual-level data from published studies and analysis using similar dosimetry and statistical methods might provide valuable insights into risks from occupational uranium and external ionizing radiation exposures.
METHODS: We pooled the data for workers from four uranium processing facilities (Fernald Feed Materials Production Center, Ohio; Mallinckrodt Chemical Works Uranium Division, Missouri; Middlesex Sampling Plant, New Jersey; and the Port Hope Radium and Uranium Refining and Processing Plant, Canada). Employment began as early as the 1930s in Canada and follow-up for vital status was as late as 2017. These facilities used similar methods to process Belgian Congo pitchblende ore which contained high concentrations of uranium, radium, and their decay products. In addition, workers were exposed to elevated levels of gamma radiation, fission product contaminants in recycled uranium and ambient radon decay products. Non-radiation exposures of industrial hygiene concern were silica dust inhalation, heavy metal toxicity from uranium, solvents, acid mists and chemicals associated with uranium processing. Exposure and outcome data were harmonized using similar definitions and dose reconstruction methods. Standardized mortality ratios (SMR) were estimated by comparing mortality in the pooled cohort with age-, sex- and calendar time-specific general population mortality rates for the U.S. and Canada.
RESULTS: Over 12,400 workers will be evaluated for cancer and non-cancer mortality in relation to exposures to uranium byproducts and gamma radiation (including ∼1,300 females). In total, death from 560 lung cancers, 503 nonmalignant respiratory diseases, 67 renal diseases, 1,596 ischemic heart diseases, and 101 dementia and Alzheimer’s diseases (AD) were detected among male workers during follow-up. Mean cumulative doses were 45 millisievert for whole-body external exposures and 172 milligray for lung dose from radon decay products. Of the 16 pooled SMRs, seven were above 1.00, none were significantly low, and only one was significantly high, i.e., dementia and AD among males (SMR =1.29; 95% confidence interval: 1.04,1.54).
CONCLUSIONS: This is the largest study to date to examine health risks in uranium processing workers (excluding uranium enrichment workers). The pooling of uranium processing worker data will address issues of importance today, specifically the concerns for cleanup workers and environmental contamination from the operation of past and present nuclear reactor and radiation facilities, reactor accidents, and possible terrorist events.
PMID:33970767 | DOI:10.1080/09553002.2021.1917786
