Why does NASA allow male astronauts to stay in space longer than female astronauts?

Under limits set by NASA in 1989, the limit for an astronaut's career is based on the risk of dying from cancer in excess of a maximum of 3% over a lifetime. That risk is assessed with a scale based on age and sex.

Every day, the Earth is surrounded by ionizing radiation, high-energy waves that can remove electrons from atoms in the body. Exposure to high levels of ionizing radiation can lead to radiation-related illness and cancer.

Female astronauts have a higher risk of radiation or cancer if they work long-term on the ISS.

Thankfully, our planet's magnetosphere and atmosphere prevent nearly all of this radiation - produced by the sun and galactic cosmic rays from exploding stars - from reaching life. on the Earth's surface.

However, on the International Space Station (ISS), which is still protected by the magnetosphere rather than the atmosphere, astronauts are exposed to higher levels of ionizing radiation, increasing their risk of developing cancer. mail during their employment.

Why is there an occupational limit to radiation exposure for male and female astronauts?

According to R. Julian Preston, a special government employee in the Radiation Protection division of the US Environmental Protection Agency, NASA's lower radiation threshold for female astronauts is based on the finding of time Over time, women are more than twice as likely to develop lung cancer than men.

In 2018, former NASA astronaut Peggy Whitson, who publicly expressed her frustration with radiation limits for female astronauts, had to retire after reaching the limit. occupational exposure to radiation at age 57.

However, NASA's radiation threshold is expected to change in the near future. In 2021, NASA asked an expert panel convened by the National Academy of Sciences, Engineering, and Medicine to evaluate the space agency's plan to change the occupational radiation limit to 600 mSv for all astronauts of all ages.

NASA has determined that limit by applying a cancer risk model to the people most at risk: novice women. NASA calculated the average risk of death from exposure for this group and converted that risk, allowing for much larger errors than was previously possible.

The 600 mSv limit is equivalent to the exposure an astronaut would receive during four six-month expeditions on the ISS.

Preston, vice chair of the National Academy's expert panel on cancer risk assessment for crewed space missions, said: 'The new limit will be reduced for some groups of men, particularly are older men. That means women can have a longer career."

Preston adds: 'To achieve parity, women may have higher limits than they can, with exposures currently higher than permitted. We discussed it as an ethical issue."

NASA's proposed plan includes waiving occupational exposure limits for longer missions, such as a final trip to Mars, which would expose astronauts to an estimated 900 mSv . However, that limit is likely lower than the 1,000 mSv occupational exposure limit that the European, Canadian and Russian space agencies currently give their astronauts.