Radiation syndromes

Acute radiation syndrome (ARS), also known as radiation sickness, is a collection of health effects due to exposure to high amounts of ionizing radiation over a short period of time. Within the first days symptoms may include nausea, vomiting, and loss of appetite. This may then be followed by a few hours or weeks with little symptoms. After this, depending on the total dose of radiation, people may develop infections, bleeding, dehydration, and confusion, or there may be a period with few symptoms. This is finally followed by either recovery or death. The symptoms can begin within one hour and may last for several months. Acute radiation syndrome (ARS), also known as radiation sickness, is a collection of health effects due to exposure to high amounts of ionizing radiation over a short period of time. Within the first days symptoms may include nausea, vomiting, and loss of appetite. This may then be followed by a few hours or weeks with little symptoms. After this, depending on the total dose of radiation, people may develop infections, bleeding, dehydration, and confusion, or there may be a period with few symptoms. This is finally followed by either recovery or death. The symptoms can begin within one hour and may last for several months. The radiation generally occurs from a source outside the body, is applied over minutes with most of the body being exposed, and involves a total dose of greater than 0.7 Gy (70 rads). It is generally divided into three types: i) bone marrow syndrome (0.7 to 10 Gy); ii) gastrointestinal syndrome (10 to 50 Gy); and iii) neurovascular syndrome (>50 Gy). Sources of such radiation may include nuclear reactors, cyclotrons, and certain devices used in cancer therapy. The cells that are most affected are generally those that are rapidly dividing. Diagnosis is based on a history of exposure and symptoms. Repeated complete blood counts (CBCs) can indicate the severity of exposure. Treatment of acute radiation syndrome is generally supportive care. This may include blood transfusions, antibiotics, colony-stimulating factors, or stem cell transplant. If radioactive material remains on the skin or in the stomach it should be removed. If radioiodine was breathed in or ingested, potassium iodide may be recommended. Complications such as leukemia and other cancers among those who survive are managed as usual. Short term outcomes depend on the exposure dose. ARS is generally rare. A single event, however, can affect a relatively large number of people. Notable cases occurred following the atomic bombing of Hiroshima and Nagasaki and the Chernobyl nuclear power plant disaster. ARS differs from chronic radiation syndrome, which occurs following prolonged exposures to relatively low doses of radiation. Classically acute radiation syndrome is divided into three main presentations: hematopoietic, gastrointestinal, and neurological/vascular. These syndromes may or may not be preceded by a prodrome. The speed of onset of symptoms is related to radiation exposure, with greater doses resulting in a shorter delay in symptom onset. These presentations presume whole-body exposure and many of them are markers that are not valid if the entire body has not been exposed. Each syndrome requires that the tissue showing the syndrome itself be exposed. The gastrointestinal syndrome is not seen if the stomach and intestines are not exposed to radiation. Some areas affected are: Early symptoms of ARS typically includes nausea and vomiting, headaches, fatigue, fever, and a short period of skin reddening. These symptoms may occur at radiation doses as low as 0.35 grays (35 rad). These symptoms are common to many illnesses, and may not, by themselves, indicate acute radiation sickness. Cutaneous radiation syndrome (CRS) refers to the skin symptoms of radiation exposure. Within a few hours after irradiation, a transient and inconsistent redness (associated with itching) can occur. Then, a latent phase may occur and last from a few days up to several weeks, when intense reddening, blistering, and ulceration of the irradiated site is visible. In most cases, healing occurs by regenerative means; however, very large skin doses can cause permanent hair loss, damaged sebaceous and sweat glands, atrophy, fibrosis (mostly keloids), decreased or increased skin pigmentation, and ulceration or necrosis of the exposed tissue. Notably, as seen at Chernobyl, when skin is irradiated with high energy beta particles, moist desquamation (peeling of skin) and similar early effects can heal, only to be followed by the collapse of the dermal vascular system after two months, resulting in the loss of the full thickness of the exposed skin. This effect had been demonstrated previously with pig skin using high energy beta sources at the Churchill Hospital Research Institute, in Oxford. According to the linear no-threshold model, any exposure to ionizing radiation, even at doses too low to produce any symptoms of radiation sickness, can induce cancer due to cellular and genetic damage. Under the assumption, survivors of acute radiation syndrome face an increased risk of developing cancer later in life. The probability of developing cancer is a linear function with respect to the effective radiation dose. In radiation-induced cancer, the speed at which the condition advances, the prognosis, the degree of pain, and every other feature of the disease are not believed to be functions of the radiation dosage. However, some studies contradict the linear no-threshold model. These studies indicate that some low levels of radiation do not increase cancer risk at all and that there may exist a threshold dosage of ionizing radiation below which exposure should be considered safe. Nonetheless, the 'no safe amount' assumption is the basis of US and most national regulatory policies regarding 'man-made' sources of radiation.