Male astronauts stay in space longer than females. Here's why

We, on Earth, are saved by the planet's magnetosphere and atmosphere from the sun's harmful radiation and galactic cosmic rays which are coming from the exploding stars.

But what about the astronauts, who are at International Space Station (ISS)?

Astronauts in ISS are exposed to higher levels of ionizing radiation which increases the risk of developing cancer throughout their careers. They are protected by the magnetosphere but not the atmosphere.

As per the limit set by NASA, astronauts' radiation exposure limit is not to exceed 3 per cent of the risk of exposure-induced death (REID) from fatal cancer over their career.

Live Science reported that risk is evaluated with a sliding scale based on age and sex, ranging from a lower career limit of 180 millisieverts (mSv) of radiation for a 30-year-old woman to an upper career limit of 700 mSv for a 60-year-old man.

It is NASA's policy to ensure a 95 per cent confidence level (CL) that this limit is not exceeded. Important to note that these limits are applicable to all missions in low Earth orbit (LEO) as well as lunar missions that are less than 180 days in duration.

Meanwhile, there is a lower career limit for radiation exposure for female astronauts than for male astronauts. Live Science reported quoting R. Julian Preston, who is a special government employee with the US Environmental Protection Agency's Radiation Protection division, that NASA's lower radiation threshold for female astronauts was based on scientific findings.

As per the report, women had more than twice the risk than men of developing lung cancer when both were exposed to high levels of radiation for similar periods.

Preston told Live Science that "it has been generally considered — based largely on the survivors from the atomic bombs in Japan — that, particularly for lung cancer, that women were more sensitive" to ionizing radiation than men were.

The limit has impacted careers also as for instance, former chief of NASA's astronaut corps Peggy Whitson had to retire in 2018 after she hit her career limit on radiation exposure at age 57. She had raised her voice over the radiation limits for female astronauts.