New NASA radiation exposure limit would bring equality to female, male astronauts
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Click here to read the Cover Story, “Experts in oncology help advise NASA on space radiation health standard for astronauts”
A committee of experts from science, medicine and academia, among other fields, has recommended NASA proceed with a proposal for a universal, career-long radiation dose limit for all astronauts.
The Committee on Assessment of Strategies for Managing Cancer Risks Associated with Radiation Exposure During Crewed Space Missions, convened at the request of NASA, concluded that the career-long dose limit should apply to both men and women, a change from previous standards, and recommended improved communication methods for advising astronauts on cancer risks.
“The old radiation standards were very restrictive for women astronauts,” Amy Berrington de González, DPhil, senior investigator and chief of the radiation epidemiology branch at the NCI and a member of the committee, told Healio | HemOnc Today. “There has been a lot of progress in understanding of radiation risk in the last few decades, so bringing that in to see whether you could make the flying time more equitable for women astronauts, I think was really important.”
Berrington de González said the universal dose was established “for the most protective case” and applied to all astronauts.
As it currently stands, men and women have different allowable doses of radiation in space travel with NASA, which were based on reported relative susceptibilities to different radiation-induced cancers. The report recommends NASA move forward with its proposed single standard dose limit for all astronauts.
“I think NASA got worried because they saw some data from the Japanese atomic bomb survivors, who we use as our primary group for determining [radiation] risk, and it looked like there was an increased risk for lung cancer among women,” committee member Gayle E. Woloschak, PhD, associate dean for graduate student and postdoctoral affairs and professor of radiation oncology and radiology at Feinberg School of Medicine at Northwestern University, told Healio | HemOnc Today. “Then the question was, ‘Should we have a different risk level for women than for men, considering Mars missions might limit a woman from going into space at all?’ And, you can imagine, there are ethical issues with that, too. Basically, we said there should be the same risks across the board for everybody.”
Before these proposals, the current standard set career exposure to radiation to not exceed 3% risk for exposure-induced death (REID) for cancer mortality at a 95 percent confidence level, to limit the cumulative effective dose received throughout an astronaut’s career.
NASA called for an independent review of the validity of the 3% REID, which has been the standard since 1989, because it is for low-Earth orbit missions exclusively. An update was necessary as NASA plans for longer-duration missions farther in the solar system.
“The radiation in deep space is different,” committee member Carol Scott-Conner, MD, PhD, MBA, emeritus professor of surgery in surgical oncology and endocrine surgery at Carver College of Medicine at University of Iowa, told Healio | HemOnc Today. “Once you get beyond the Earth’s magnetosphere, you get highly energetic particles from the sun. And these are things like the nuclei of iron. You can think of them as like cannon balls going through cells, as opposed to protons, electrons or gamma rays that we think of here on Earth. ... If you go to Mars, and let’s say it takes you about 6 months, you're exposed that whole time to this radiation.”
The committee also recommended NASA provide all its astronauts with individual radiation risk assessment (based on age and sex), communicate a comprehensive picture of an astronaut’s own cancer risk, and continue to discuss changes in radiation risk during routine health briefings.
References:
Space radiation and astronaut health: Managing and communicating cancer risks. https://www.nap.edu/resource/26155/Space-Radiation-Study_Report-Highlights.pdf. Published June 2021. Accessed Oct. 22, 2021.
NASA should update astronaut radiation Exposure Limits, Improve Communication of Cancer Risks. https://www.nationalacademies.org/news/2021/06/nasa-should-update-astronaut-radiation-exposure-limits-improve-communication-of-cancer-risks. Published June 24, 2021. Accessed Oct. 25, 2021.
For more information:
Amy Berrington de González, DPhil, can be reached at Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 9609 Medical Center Drive, MSC 9778, Bethesda, MD 20892-9778; email: berringtona@mail.nih.gov.
Carol Scott-Conner, MD, PhD, MBA, can be reached at Department of Surgery, University of Iowa Roy J. and Lucille A. Carver College of Medicine, 375 Newton Road, Iowa City, IA 52242; email: carol-scott-conner@uiowa.edu.
Gayle E. Woloschak, PhD, can be reached at Department of Radiation Oncology, Feinberg School of Medicine, Northwestern University, 420 E. Superior St., Chicago, IL 60611; email: g-woloschak@northwestern.edu.
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