NASA wants to set a new radiation limit for astronauts

Now that the The Biden administration has signaled its support for NASA’s Artemis mission to the moon, perhaps we should think about the risks astronauts will face when they get there and what could happen during a longer trip to Mars.

Of all the things to worry about while traveling through space – equipment breakdowns, the strange effects of weightlessness, collisions with space debris, and just being away – one of the hardest to deal with is health effects. of solar or cosmic radiation. events. This radiation consists of atoms that have lost their electrons as they accelerate in interstellar space, approaching the speed of light, something that happens right after a star explodes, for example. It comes in three forms: particles trapped in Earth’s magnetic field; particles launched into space during solar flares; and galactic cosmic rays, which are high-energy protons and heavy ions from outside our solar system.

It is also one of the “red risks” identified by a NASA study published last year of the highest priority health problems facing astronauts. Radiation damages DNA and can cause mutations that can lead to cancers. It can also cause cardiovascular health problems like heart damage, narrowing of arteries and blood vessels, and neurological problems that can lead to cognitive decline, according to a NASA website.

On Earth, humans are exposed to 3 to 4 millisieverts (mSv) of radiation per year, mainly from natural sources such as some types of rocks and the few cosmic rays that pass through the atmosphere. On the International Space Station, astronauts get around 300 mSv per year. Until now, a 55-year-old NASA astronaut was limited to an effective dose of 400 mSv during his career, while a 35-year-old astronaut could only be exposed to 120 mSv.

Now that NASA plans to send people on much longer missions, the agency is considering raising that threshold to 600 mSv for astronauts of any gender or age. By the existing standard, some veteran astronauts might have been barred from longer-term space missions because they are hitting radiation limits for life. Younger astronauts have less flight time in space and therefore less exposure, but the success of a large mission may require experience on the young.

The new limit proposed by NASA would still be lower than that of other space agencies; European, Russian and Canadian astronauts can be exposed to up to 1,000 mSv before they are dropped off by their space officials. But NASA officials are unapologetic about their more conservative stance. “It’s a different risk posture in what we think is an acceptable risk,” says David Francisco, technical fellow for manned spaceflight standards in NASA’s Office of the Medical Director. “We chose 600 because we think it is more acceptable to our culture. It is something that we constantly work on and that we come and go. We debated going to 1,000, and that’s one of the questions: Are we still conservative at 600? ”.

To answer that question, the space agency has asked a panel of experts from the National Academy of Sciences to determine the best number to use. The panel began meeting last month and is expected to complete its work this summer. Experts will discuss how NASA has calculated its new exposure limits and how they match up with existing clinical data and animal studies.

To understand the links between radiation and cancer, medical researchers have long been following the survivors of the atomic bomb explosions in Japan during World War II (as well as the health of their children). There have also been studies of medical workers who are exposed to X-rays and nuclear plant workers, who receive low doses of radiation throughout their careers. But NASA doesn’t have much data on the effects of radiation from space on the health of its astronauts.


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