The Biological timeline of radiation poisoning describes the phenomenon where, following a dose of ionizing radiation, a person may have a period of apparent health, lasting for days or weeks, despite a surely terminal illness. The lag time of the effects of even severe radiation poisoning are a result of many biological processes, manifesting damage in different ways.
The amount of time between exposure to radiation and the onset of the initial symptoms may be an indicator of how much radiation was absorbed.[1] Symptoms appear sooner with higher doses of exposure.[2] The symptoms of radiation sickness become more serious (and the chance of survival decreases) as the dosage of radiation increases. A few symptom-free days may pass between the appearance of the initial symptoms and the onset of symptoms of more severe illness associated with higher doses of radiation.[1]
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Nausea and vomiting generally occur within 24–48 hours after exposure to mild (1–2 Gy) doses of radiation. Headache, fatigue, and weakness are also seen with mild exposure.[1] Moderate (2–3.5 Gy of radiation) exposure is associated with nausea and vomiting beginning within 12–24 hours after exposure.[1] In addition to the symptoms of mild exposure, fever, hair loss, infections, bloody vomit and stools, and poor wound healing are seen with moderate exposure.[1] Nausea and vomiting occur in less than 1 hour after exposure to severe (3.5–5.5 Gy) doses of radiation, followed by diarrhea and high fever in addition to the symptoms of lower levels of exposure.[1] Very severe (5.5–8 Gy of radiation) exposure is followed by the onset of nausea and vomiting in less than 30 minutes followed by the appearance of dizziness, disorientation, and low blood pressure in addition to the symptoms of lower levels of exposure.[1]
While the irradiation has resulted in bone marrow destruction and death of many rapidly multiplying cells, the surface effects do not become apparent until later. For example, irradiation kills the rapidly dividing cells of the gastrointestinal tract; however, diarrhea is not apparent until the cells begin to slough off, coming out in bloody excrement. Loss of this protective lining exposes the body to bacteria within the gut causing sepsis. Also, this causes an inability to absorb nutrition from food. This is the same with the rapidly proliferating cells of the immune system. Irradiation essentially halts white blood cell production by destroying bone marrow, however the remaining white blood cells within the body are still temporarily working, until they are "used up". Anemia develops more slowly, because preexisting red blood cells have a longer life span than white blood cells and platelets.[3]
Depending on the conditions of the exposure, several post-latent symptoms may occur:
The prognosis is generally terminal. Given that there is no possibility of recovery, all current medical treatments are palliative, e.g., pain management using morphine and similarly powerful analgesic, sedative or hypnotic drugs.
Radiation dermatitis from lower-level exposures usually manifests only after 2 months.[4] Radiation acne is a cutaneous condition characterized by comedo-like papules occurring at sites of previous exposure to therapeutic ionizing radiation, skin lesions that begin to appear as the acute phase of radiation dermatitis begins to resolve.[5] Radiation recall reactions occur months to years after radiation treatment.[6] Radiation cancer may occur following ionizing radiation exposure following a latent period averaging 20 to 40 years.[6]:40[7]
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