Findings inform radiation protection methods including those for NASA astronauts bound for Mars mission

Sep 19, 2018

OAK RIDGE, Tenn.—When data on one million workers is studied, you’re bound to find better methods for radiation protection and uncover answers to elusive questions like “what is the cancer and/or mortality risk when exposure is received gradually over time rather than briefly as for the atomic bomb survivors?”

These and many other radiation protection, occupational exposure, and radiation-induced cancer risk questions are being answered by a team of health physicists, epidemiologists, industrial hygienists and other experts leading research in the Million Worker Study (MWS). The MWS began nearly 25 years ago looking at exposure cohorts of workers from DOE, NRC, DOD and other workers from nuclear power plants, physicians and health professionals working with medical radiation, and even nuclear weapons test participants. One by one, through the years, these cohorts have been studied for instances of cancer or death based on their occupational and other exposures received either acutely or over time.

In 2018, the team, which includes experts from ORISE, has been looking specifically at mortality among workers at Mallinckrodt Chemical Works (MCW), a key study group with complex exposures. In 1942, 40 tons of uranium oxide were used by Enrico Fermi to generate the first manmade nuclear reaction, which ushered in the atomic age. The uranium oxide was produced by workers at MCW. By studying mortality rates and reconstructed radiation organ doses on 2,500 MCW workers, the Million Worker Study team has been able to learn more about the effects of six different types of exposures to these workers. These exposures include external gamma ray exposures from uranium and radium; medical xrays from occupationally required chest exams; and inhalation of uranium and silica dust from the work environment.

Even though these exposures at Mallinckrodt occurred more than 75 years ago, what we can learn from them continues to inform our understanding of radiation exposures and health outcomes and instructs our radiation protection measures. From the Mallinckrodt study, and other groups like it, NASA is looking at how workers were exposed to radiation over time, and how that might correlate to astronauts’ exposures while traveling through space on Mars missions. An overview of the Million Worker Study involving the Mallinckrodt Chemical Works cohort was published in the April 2018 edition of Health Physics. ORISE experts Betsy Ellis, Ph.D., Ashley Golden, Ph.D., and David Girardi were contributing authors.

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The Oak Ridge Institute for Science and Education (ORISE) is a U.S. Department of Energy (DOE) asset that is dedicated to enabling critical scientific, research, and health initiatives of the department and its laboratory system by providing world class expertise in STEM workforce development, scientific and technical reviews, and the evaluation of radiation exposure and environmental contamination. 

ORISE is managed by ORAU, a 501(c)(3) nonprofit corporation and federal contractor, for DOE’s Office of Science. The single largest supporter of basic research in the physical sciences in the United States, the Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit