University of Iowa professor helps advise NASA on astronaut cancer risk

IOWA CITY — NASA’s Perseverance rover and Ingenuity helicopter have been exploring Mars since Feb. 18. Elon Musk said he’s “highly confident” his SpaceX will launch people toward the Red Planet by 2026 or sooner.

And a growing number of private spaceflight companies are eyeing manned missions closer to home — upping the cosmic chatter that’s normalizing the notion of civilian space excursion.

All the talk of sending more people into space — some beyond the Van Allen radiation belts — has NASA thinking more intentionally about the risk of cancer-causing radiation exposure to astronauts; what constitutes an acceptable level; how to communicate risks; and when and how to take them.

“NASA sets standards or limits for all the different adverse exposures associated with exposure to the space environment,” University of Iowa surgical oncology professor emeritus Carol Scott-Conner said. “Whether it's the International Space Station, or going back to the moon … or going to Mars.”

NASA has been weighing whether to update its “space radiation health standard” to make it more inclusive and more informative, given astronauts — especially those eyeing longer distances, such as to the moon or Mars — are at greater risk of cancer due to radiation exposure during space flight.

Astro-equality

The Committee on Assessment of Strategies for Managing Cancer Risk Associated With Radiation Exposure During Crewed Space Missions — composed of 18 members, including Iowa’s Scott-Conner — in June issued a report supporting a NASA radiation standard update.

The update would move NASA away from its old model of setting dose limits based on risk for different genders and ages to a new set universal career-long radiation dose limit of 600 millisieverts.

“This dose limit should apply to all astronauts, regardless of gender and age, which would help promote equal opportunity for mission assignment and for participation in longer spaceflights,” according to a new release from the National Academies of Sciences, Engineering and Medicine.

Under the current quantifiable standard, a male astronaut could reach his career radiation-exposure limit with a 211-day mission to the International Space Station, while a woman could hit her limit with a 43-day mission.

“A single radiation standard that applies to all astronauts regardless of sex and age would provide equality of opportunity,” according to the NASA committee’s report. “The current standard limits female astronauts to shorter spaceflight careers, based on data indicating that females have a reported increase of some specific cancers from exposure to ionizing radiation compared to males.”

Taking risks

The new standard is more conservative, as it was determined using the risk model for the most-susceptible person — a 35-year-old woman — according to Scott-Conner, who joined UI Health Care in 1995 and served as Department of Surgery chair and in surgical oncology before retiring six years ago.

She was added to the NASA committee around December to help evaluate not only the proposed set radiation limit but how the administration communicates cancer risk to astronauts.

“The committee concluded that astronauts who travel on long-duration spaceflight missions are likely to be exposed to radiation levels that exceed the proposed standard and recommended that NASA develop a protocol for waiver of the proposed space radiation standard that is judicious, transparent and informed by ethics,” according to the committee report.

As precursor to such a radiation-risk waiver process, the committee advised NASA do a better job assessing individual risk and communicating about its radiation health standards.

“A key component of risk management is evidence-based, thorough and effective communication of the risks,” according to the report.

“In the context of NASA’s space radiation standard, risk management requires an understanding of the risks and the standard itself, as well as an understanding of how astronauts understand and interpret the risks, related standards, and both formal and informal communications about them.”

Commercial space flight

Although commercial space flight has been a hot topic recently — driving more discussion about cosmic pursuits in general — the committee’s recommendations are for NASA alone.

The Federal Aviation Administration, not NASA, regulates commercial space flight.

Those flights — such as Jeff Bezos’ Blue Origin space mission planned for July 20 or Richard Branson’s aboard a Virgin Galactic vessel next week — will pass through U.S. airspace during takeoff and reentry but stay well within the Van Allen radiation belts.

In that trips of that nature are shorter and closer to Earth, Scott-Conner said, radiation exposure is less. In addition, NASA astronauts are “employees” — meaning they’d be protected by the Occupational Safety and Health Administration.

Passengers on commercial flights are not, according to Scott-Conner.

Exposure

Spaceflight radiation risks come in the form of “background galactic radiation” — such as from the sun, Scott-Conner said. And the Van Allen radiation belts — discovered by famed UI professor James Van Allen — capture those particles, protecting the Earth. That’s why moving beyond them heightens the risk.

“When an astronaut is up on the International Space Station, they're still inside the magnetic shield protection,” she said. “But once they get outside of that — to go to the moon or to go to Mars — then all these energetic particles from the sun and the galactic background … they’re exposed.”

Due to the limited number of astronauts who’ve explored space, researchers don’t have a huge body of data to assess the risk or the type of cancer they could develop. But researchers analyzed atomic bomb survivors for comparison.

“Lung cancer is one of the ones that showed up in the atomic bomb survivors,” Scott-Conner said. “But a lot of them are smokers.”

She also noted heightened risk for blood or bone cancers, as well as breast cancer, but noted bomb survivors are not a perfect comparison.

“That's a simple intense exposure,” she said. “When you talk about astronauts, it’s really a different environment. The kind of radiation that they would be exposed to is different.

“And it’s more of a constant increased level of radiation for however many months they might be traveling in space.”

Ionizing radiation can lead to other long-term health problems, too, experts reported, including heart concerns and cataracts.

“NASA should continuously strive to base its standards on the best available science as it embarks on this new phase of space travel and exploration,” Hedvig Hricak, chairwoman of the radiology department at Memorial Sloan Kettering Cancer Center and chairwoman of the committee that wrote the report, said in a statement.

“As science on radiation-related cancer risks is constantly evolving, NASA has an important opportunity to revisit its space radiation health standard,” she said.

Vanessa Miller covers higher education for The Gazette.

Comments: (319) 339-3158; vanessa.miller@thegazette.com