New radiation limits for astronauts could make spaceflight fairer

Setting a universal life time radiation dose would allow men and women to spend an equal time in space

Credit: NASA
Published: June 24, 2021 at 4:00 pm
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NASA astronauts should have the same radiation limit, regardless of their age or gender, according to a new report the agency commissioned from the National Academies of Sciences, Engineering and Medicine, which was published on 24 June 2021.


High-exposure to the radiation found in space can increase the risk of long-term health effects such as cancer, heart problems and cataracts.

Here on Earth, we are protected from space radiation by the planet’s magnetic field and thick atmosphere, but the same is not true of astronauts.

To limit these risks, NASA limits how long astronauts can stay in space exposed to this radiation.

How much radiation are astronauts allowed to be exposed to?

The report suggests that astronauts should be exposed to no more than 600 milliSieverts (mSv) of radiation over their entire career.

This is the equivalent of spending almost four years on the International Space Station.

The station, however, is still within the Earth’s protective magnetic bubble.

As NASA is currently making plans to go further away from Earth – such as the planned human mission to the Moon, Artemis – the agency is reconsidering how it approaches the risk of radiation.

“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,” says Hedvig Hricak, from Memorial Sloan Kettering Cancer Center, who chaired the committee who 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.”

How do NASA decide how much radiation its astronaut can have?

The radiation limits are based on research looking at a wide variety of people exposed to radiation – including past astronauts.

The longer an astronaut is in space, the more radiation they are exposed too, meaning the radiation limit sets the amount of time they can spend in space.

Currently, however, this limit is adjusted for factors such as age and gender, the result of which is that women astronauts aren’t allowed to spend as long in space as men.

To make spaceflight farer, the report instead set a new universal limit, based on the risk to a 35-year old woman, the group considered most susceptible to radiation induced cancer.

Will radiation stop astronauts from going to the Moon? Or Mars?

The new radiation limit will still allow for astronauts to go to the Moon on the Artemis mission.

During the Apollo mission, the moonwalkers were still only exposed to a few dozen milliSieverts of radiation, meaning future lunar explorers could still spend some time on the surface with little ill-effect.


The new limit might pose a problem for future missions to Mars, however, as these will subject astronauts to around 1000mSv of radiation, unless NASA are able to reduce the radiation through technologies such as shielding.


Ezzy Pearson is the News Editor of BBC Sky at Night Magazine. Her first book about the history of robotic planetary landers is out now from The History Press.

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