Space may be pretty, but it’s dangerous. Astronauts face a much higher dose of ionizing radiation than us Earth-bound folks, and a new report says that NASA’s current guidelines and risk assessment methods are in serious need of an update.
On the surface of the Earth, protected by our extensive magnetic field and layers of thick atmosphere, we experience about 2-3 milliSieverts (mSv) of radiation exposure every year. Even that background level is enough to trigger the occasional cancer growth.
But astronauts, especially those hoping to go on upcoming long-term missions to the Moon and Mars, face a much greater risk due to the high-energy, ionizing radiation constantly soaking every cubic centimeter of space. To mitigate that risk, NASA currently implements a system based on “risk of exposure-induced death” (REID). The space agency estimates the exposure for each astronaut based on their sex, and if the REID exceeds 3%, their spacefaring careers are over.
However, a new report issued by the National Academies of Sciences, Engineering, and Medicine recommends that NASA update its guidelines. Instead, NASA should implement a single, uniform limit of 600 mSv, which would represent a 3% REID for a 35 year old female astronaut (considered the most suspectible group).
“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,” said Hedvig Hricak, chair of the department of radiology at Memorial Sloan Kettering Cancer Center, and chair of the committee that wrote the report. “As science on radiation-related cancer risks is constantly evolving, NASA has an important opportunity to revisit its space radiation health standard. We hope this report will guide NASA in protecting the health of astronauts throughout their careers.”
The new limits would allow female astronauts to run longer missions, but would put them at higher risk at the end of their careers.
To help alleviate that concern, the report recommended that NASA measure and communicate the risk levels to astronauts on an individual, not group, basis. Each astronaut should know their current exposure and the risks that represents for them. They should then be given the freedom to take on the additional risk.
“The risks of space travel are borne by a small group of astronauts, but all of society benefits — from the technological advances, new scientific knowledge, and the national and international pride and collaboration,” said R. Julian Preston, committee vice chair and special government employee in the Radiation Protection Division of the U.S. Environmental Protection Agency. “But as missions go deeper into space, we need to communicate why astronauts are being asked to take on that risk, and offer explicit ethical justifications. This report offers a framework for accomplishing that.”