MELISSA BLOCK, HOST:
Some day, astronauts may venture out to places where no humans have gone before, for instance, an asteroid. The men and women on these missions could face unknown risks to their physical and psychological health.
NPR's Nell Greenfieldboyce reports that NASA recently asked for advice on how to decide whether a mission is worth the potential danger.
NELL GREENFIELDBOYCE, BYLINE: Astronauts aren't covered by the usual safety regulations that apply to earthbound jobs.
JEFFREY KAHN: NASA is exempted from those rules. But they're required to make their own rules.
GREENFIELDBOYCE: Jeffrey Kahn is a bioethicist at Johns Hopkins University. He says NASA hopes to astronauts will eventually go far out into space.
KAHN: So think about going to Mars, nine months one-way.
GREENFIELDBOYCE: Those trips could mean putting astronauts at greater risk than NASA's rules currently allow. Possible dangers include things like weakened bones, radiation exposure, the psychological effects of isolation, plus all the unknown risks.
Kahn recently chaired a committee of ethicists, astronauts, doctors and others, convened by the Institute of Medicine. NASA asked it to tackle this question...
KAHN: What happens when sending people out into space would exceed the existing health standards? What should they do?
GREENFIELDBOYCE: The answers are in a new report. It says NASA should keep its current healthcare standards but make exceptions on a mission by mission basis, after considering a set of ethical principles. Things like balancing the risk of harm with the potential benefit, and making sure that women get a fair shot at being part of a crew.
KAHN: Now, because of the health standards for exposure to ionizing radiation, women are allowed to spend fewer days in space than are men.
GREENFIELDBOYCE: NASA's Chief Health and Medical Officer is Rich Williams. He says that NASA currently sets the same risk limit from radiation for both men and women. But because women are more vulnerable to radiation-induced cancer, they'll reach that limit sooner.
RICH WILLIAMS: It's not been a problem up until now and in the future, because we never got close to radiation limits.
GREENFIELDBOYCE: William says longer missions will push those limits, so this is one of the reasons NASA wanted outside advice.
WILLIAMS: We are all interested and committed to limiting the risk to the greatest extent possible, but also to actually completing and doing the missions.
GREENFIELDBOYCE: The astronauts have their own views on risks. Ed Lu is a former astronaut who spent six months on the International Space Station. He says astronauts accept health standards for things that could affect a mission's success, like eyesight.
ED LU: But there are other standards which we all had a problem with, I think. And they had to do with ones that are things for your, quote, "your own good."
GREENFIELDBOYCE: Like whether an increased risk of cancer years in the future is worth the chance to do a mission.
LU: Decisions like that ought to be up to the astronaut.
GREENFIELDBOYCE: But this committee said first, NASA has to decide whether it's really OK to ask someone to take those risks.
Nell Greenfieldboyce, NPR News.