Ionizing radiation--the type emitted from X-rays, gamma rays and alpha and beta particles released from radioactive material--is dangerous to living organisms. It can penetrate cells, causing chemical damage, and result in radiation poisoning (also known as radiation sickness). Radiation poisoning usually occurs in those exposed to large amounts of radiation over a short period, known as acute exposure. The severity of the poisoning depends upon the amount; radiation is measured in units called grays (Gy) and length of exposure.
Mild Symptoms
Because the cells that line the intestines are very susceptible to damage from radiation, the first symptoms to appear in most cases of radiation poisoning are nausea and vomiting. The amount of time from the exposure to the onset of vomiting is a direct indicator to how much radiation the patient absorbed.
Mild radiation sickness occurs in those who have been exposed to 1 Gy to 2 Gy of radiation. The onset of nausea and vomiting in this case is usually between 24 to 48 hours, according to doctors at the Mayo Clinic. Other symptoms may occur, including headache, fatigue and general weakness. These symptoms may not appear for several days after the initial nausea and vomiting.
Moderate Symptoms
Patients with moderate radiation poisoning were likely exposed to 2 Gy to 3.5 Gy of radiation. With these higher doses, nausea and vomiting appears between 12 to 24 hours after the initial exposure. Patients may then have several days without additional signs of illness before exhibiting more severe symptoms.
Patients with moderate radiation sickness--in addition to the symptoms listed for mild sickness--have fever and hair loss, as the radiation damages the cells of the hair follicles. Radiation also causes damage to blood cells, including white cells. This results in an increased risk of infections, causing poor wound healing. The additional damage to the cells in the intestines leads to vomiting blood and bloody diarrhea.
Severe Symptoms
Patients exposed to 3.5 Gy to 5.5 Gy of radiation begin vomiting within one hour of the exposure. In addition to the symptoms listed for both mild sickness and moderate sickness, patients may exhibit a high fever and diarrhea. Doctors at the Mayo Clinic say severe radiation sickness is fatal in about 50 percent of patients.
Very Severe Symptoms
Very severe, and usually fatal, radiation poisoning occurs when someone is exposed to 5.5 Gy to 8 Gy of radiation. In these cases, nausea and vomiting begin within 30 minutes of exposure, followed by disorientation, dizziness and low blood pressure (hypotension).
