Which dose range is considered lethal with no treatment for radiation exposure?

The range of 400-500 Rem is considered lethal with no treatment for radiation exposure due to the severe biological effects that such high doses of radiation can inflict on the human body. At levels within this range, individuals are likely to experience acute radiation syndrome (ARS), which can cause widespread cellular damage, particularly to tissues with rapidly dividing cells like those in the gastrointestinal tract and bone marrow. This level of exposure can disrupt critical bodily functions, leading to serious health consequences, including organ failure and death without prompt and effective medical intervention.

Understanding radiation dose effects helps emphasize the importance of maintaining radiation exposure as low as reasonably achievable (ALARA) to protect individuals from the potential dangers of excessive radiation, especially for those working in fields like medical imaging or radiation therapy.