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.

Among all the things to worry about when traveling in space – equipment malfunctions, the weird effects of weightlessness, collisions with space debris, and being far away – l one of the most difficult to deal with is the health effects of solar or cosmic radiation. events. This radiation is made up of atoms that have lost their electrons as they accelerate through 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 the earth’s magnetic field; particles projected 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 on the highest priority health problems facing astronauts. Radiation damages DNA and can lead to mutations that can trigger cancer. It can also lead to cardiovascular health issues such as heart damage, narrowing of arteries and blood vessels, and neurological issues that can lead to cognitive impairment, according to a NASA website.

On Earth, humans are exposed to 3 to 4 millisieverts (mSv) of radiation per year, mostly from natural sources like certain kinds of rocks and the few cosmic rays that pass through the atmosphere. On the International Space Station, astronauts receive about 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. Under the existing standard, some veteran astronauts may have been excluded from longer-term space missions because they encounter lifetime radiation limits. Young astronauts have less time in space and therefore less exposure, but the success of a large mission may require experience compared to young people.

The new limit proposed by NASA would always be lower than those of other space agencies; European, Russian and Canadian astronauts can be exposed to up to 1000 mSv before being immobilized by their space agents. But NASA officials don’t apologize for their more conservative stance. “It’s a different risk posture in what we feel is an acceptable risk,” says David Francisco, technical researcher for human space flight standards in the office of the chief medical officer at NASA. “We chose 600 because we think it’s more acceptable for our culture. It’s something that we are constantly working on and going back and forth. We’ve been debating going to 1,000, and that’s one of the questions: are we still conservative with 600? “

To resolve this question, the space agency asked a group of experts from the National Academy of Sciences to determine which number is best to use. The group started meeting last month and is expected to complete its work by this summer. Experts will examine how NASA calculated its new exposure limits and how these match up with existing clinical data and animal studies.

To understand the links between radiation and cancer, medical researchers have long followed the survivors of atomic bomb blasts in Japan during World War II (as well as the health of their children). Studies have also been carried out with medical workers exposed to x-rays and nuclear power plant workers, who receive low doses of radiation during their careers. But NASA doesn’t have a lot of data on the health effects of radiation from space on its astronauts.