High Quality Content by WIKIPEDIA articles! Astronauts are exposed to approximately 50-2,000 mSv (mili-Sievert) while on missions to the International Space Station (ISS), the moon and beyond. The risk of cancer caused by ionizing radiation is well documented at radiation doses beginning at 50 mSv and above. Studies have shown that survivors of the atomic bomb explosions in Hiroshima and Nagasaki, nuclear reactor workers and patients who have undergone therapeutic radiation treatments have received low-linear energy transfer (LET) radiation (x-rays and gamma rays) doses in the same 50-2000 mSv range.