The amount of radiation your body absorbs is measured in a unit called gray, abbreviated as Gy. We're exposed to very low levels of radiation during some common procedures such as medical or dental X-rays; these very low doses don't cause radiation sickness. The effects of acute radiation exposure typically appear when the whole body has absorbed a dose measuring at least 1 Gy. Exposures between 1 and 8 Gy can usually be treated, while exposures greater than 8 Gy are often not treatable, leading to death within several days or weeks. Exposures of these levels are usually associated with a malfunctioning X-ray equipment, accidents at nuclear facilities and detonation of radioactive material.
Initial Symptoms
Nausea and vomiting are usually the first symptoms in a case of radiation sickness. Symptoms may appear then subside for a few days, giving an appearance of apparent health and well-being. Symptoms then reappear after this brief period. Severe radiation sickness results in death about half the time, while those who are particularly sensitive to radiation exposure may die from moderate exposure.
Continuing Symptoms
Symptoms of mild radiation exposure are typically limited to nausea and vomiting, headache, fatigue and weakness. Higher levels of exposure may result in symptoms such as fever, hair loss, bloody vomit or stool, diarrhea, blistering or scalding of the skin and pour wound healing. Dizziness, disorientation, weight loss, headache and low blood pressure may also result.
Long-term Symptoms
Radiation exposure may also have continuing long-term effects such as skin conditions, cancer, inflammation of the sac around the heart, poor growth or birth defects in children, reproductive dysfunction, kidney, liver or gastrointestinal problems and central nervous system diseases.
Severity
The time between radiation exposure and onset of nausea and vomiting gives a good indication of how much radiation was absorbed, according to the Mayo Clinic. If symptoms present within an hour of exposure, the radiation exposure is severe, of an estimated 3.5 to 5.5 Gy; symptoms within less than 30 minutes indicate very severe exposure of greater than 5.5 Gy. Symptoms within 12 to 24 hours of exposure indicate a moderate exposure level of perhaps 2 to 3.5 Gy, and nausea and vomiting that do not appear until 24 to 48 hours have passed indicate a relatively mild case that may include absorption of 1 to 2 Gy.
