Acute radiation syndrome


Acute radiation syndrome, also known as radiation sickness or radiation poisoning, is a collection of health effects that are caused by being exposed to high amounts of ionizing radiation in a short period of time. Symptoms can start within an hour of exposure, and can last for several months. Early symptoms are usually nausea, vomiting and loss of appetite. In the following hours or weeks, initial symptoms may appear to improve, before the development of additional symptoms, after which either recovery or death follows.
ARS involves a total dose of greater than 0.7 Gy, that generally occurs from a source outside the body, delivered within a few minutes. Sources of such radiation can occur accidentally or intentionally. They may involve nuclear reactors, cyclotrons, certain devices used in cancer therapy, nuclear weapons, or radiological weapons. It is generally divided into three types: bone marrow, gastrointestinal, and neurovascular syndrome, with bone marrow syndrome occurring at 0.7 to 10 Gy, and neurovascular syndrome occurring at doses that exceed 50 Gy. The cells that are most affected are generally those that are rapidly dividing. At high doses, this causes DNA damage that may be irreparable. Diagnosis is based on a history of exposure and symptoms. Repeated complete blood counts can indicate the severity of exposure.
Treatment of ARS is generally supportive care. This may include blood transfusions, antibiotics, colony-stimulating factors, or stem cell transplant. Radioactive material remaining on the skin or in the stomach should be removed. If radioiodine was inhaled or ingested, potassium iodide is recommended. Complications such as leukemia and other cancers among those who survive are managed as usual. Short-term outcomes depend on the dose exposure.
ARS is generally rare. A single event can affect a large number of people. The vast majority of cases involving ARS, alongside blast effects, were inflicted by the atomic bombings of Hiroshima and Nagasaki, with post-attack deaths in the tens of thousands. Nuclear and radiation accidents and incidents sometimes cause ARS; the worst, the Chernobyl nuclear power plant disaster, caused 134 cases and 28 deaths. ARS differs from chronic radiation syndrome, which occurs following prolonged exposures to relatively low doses of radiation, and from radiation-induced cancer.

Signs and symptoms

Classically, ARS is divided into three main presentations: hematopoietic, gastrointestinal, and neurovascular. These syndromes may be preceded by a prodrome. The speed of symptom onset 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 invalid if the entire body has not been exposed. Each syndrome requires that the tissue showing the syndrome itself be exposed. Some areas affected are:
  1. Hematopoietic. This syndrome is marked by a drop in the number of blood cells, called aplastic anemia. This may result in infections, due to a low number of white blood cells, bleeding, due to a lack of platelets, and anemia, due to too few red blood cells in circulation. These changes can be detected by blood tests after receiving a whole-body acute dose as low as, though they might never be felt by the patient if the dose is below. Conventional trauma and burns resulting from a bomb blast are complicated by the poor wound healing caused by hematopoietic syndrome, increasing mortality.
  2. Gastrointestinal. This syndrome often follows absorbed doses of. The signs and symptoms of this form of radiation injury include nausea, vomiting, loss of appetite, and abdominal pain. Vomiting in this time-frame is a marker for whole body exposures that are in the fatal range above. Without exotic treatment such as bone marrow transplant, death with this dose is common, due generally more to infection than gastrointestinal dysfunction.
  3. Neurovascular. This syndrome typically occurs at absorbed doses greater than, though it may occur at doses as low as. It presents with neurological symptoms such as dizziness, headache, or decreased level of consciousness, occurring within minutes to a few hours, with an absence of vomiting, and is almost always fatal, even with aggressive intensive care.
Early symptoms of ARS typically include nausea, vomiting, headaches, fatigue, fever, and a short period of skin reddening. These symptoms may occur at radiation doses as low as. These symptoms are common to many illnesses, and may not, by themselves, indicate acute radiation sickness.

Dose effects

A similar table and description of symptoms, derived from data from the effects on humans subjected to the atomic bombings of Hiroshima and Nagasaki, the indigenous peoples of the Marshall Islands subjected to the Castle Bravo thermonuclear bomb, animal studies and lab experiment accidents, have been compiled by the U.S. Department of Defense.
A person who was less than from the atomic bomb Little Boy hypocenter at Hiroshima, Japan, was found to have absorbed about 9.46 grays of ionizing radiation. The doses at the hypocenters of the Hiroshima and Nagasaki atomic bombings were 240 and 290 Gy, respectively.

Skin changes

refers to the skin symptoms of radiation exposure. Within a few hours after irradiation, a transient and inconsistent redness 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, decreased or increased skin pigmentation, and ulceration or necrosis of the exposed tissue.
As seen at Chernobyl, when skin is irradiated with high energy beta particles, moist desquamation 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. Another example of skin loss caused by high-level exposure of radiation is during the 1999 Tokaimura nuclear accident, where technician Hisashi Ouchi had lost a majority of his skin due to the high amounts of radiation he absorbed during the irradiation. This effect had been demonstrated previously with pig skin using high energy beta sources at the Churchill Hospital Research Institute, in Oxford.

Cause

ARS is caused by exposure to a large dose of ionizing radiation over a short period of time. Alpha and beta radiation have low penetrating power and are unlikely to affect vital internal organs from outside the body. Any type of ionizing radiation can cause burns, but alpha and beta radiation can only do so if radioactive contamination or nuclear fallout is deposited on the individual's skin or clothing.
Gamma and neutron radiation can travel much greater distances and penetrate the body easily, so whole-body irradiation generally causes ARS before skin effects are evident. Local gamma irradiation can cause skin effects without any sickness. In the early twentieth century, radiographers would commonly calibrate their machines by irradiating their own hands and measuring the time to onset of erythema.

Accidental

Accidental exposure may be the result of a criticality or radiotherapy accident. There have been [|numerous] criticality accidents dating back to atomic testing during World War II, while computer-controlled radiation therapy machines such as Therac-25 played a major part in radiotherapy accidents. The latter of the two is caused by the failure of equipment software used to monitor the radiational dose given. Human error has played a large part in accidental exposure incidents, including some of the criticality accidents, and larger scale events such as the Chernobyl disaster. Other events have to do with orphan sources, in which radioactive material is unknowingly kept, sold, or stolen. The Goiânia accident is an example, where a forgotten radioactive source was taken from a hospital, resulting in the deaths of 4 people from ARS. Theft and attempted theft of radioactive material by clueless thieves has also led to lethal exposure in at least one incident.
Exposure may also come from routine spaceflight and solar flares that result in radiation effects on earth in the form of solar storms. During spaceflight, astronauts are exposed to both galactic cosmic radiation and solar particle event radiation. The exposure particularly occurs during flights beyond low Earth orbit. Evidence indicates past SPE radiation levels that would have been lethal for unprotected astronauts. GCR levels that might lead to acute radiation poisoning are less well understood. The latter cause is rarer, with an event possibly occurring during the solar storm of 1859.

Intentional

Intentional exposure is controversial as it involves the use of nuclear weapons, human experiments, or is given to a victim in an act of murder. The intentional atomic bombings of Hiroshima and Nagasaki resulted in tens of thousands of casualties; the survivors of these bombings are known today as. Nuclear weapons emit large amounts of thermal radiation as visible, infrared, and ultraviolet light, to which the atmosphere is largely transparent. This event is also known as "flash", where radiant heat and light are bombarded into any given victim's exposed skin, causing radiation burns. Death is highly likely, and radiation poisoning is almost certain if one is caught in the open with no terrain or building masking-effects within a radius of 0–3 km from a 1megaton airburst. The 50% chance of death from the blast extends out to from a 1megaton atmospheric explosion.
Scientific testing on humans within the United States occurred extensively throughout the atomic age. Experiments took place on a range of subjects including, but not limited to; the disabled, children, soldiers, and incarcerated persons, with the level of understanding and consent given by subjects varying from complete to none. Since 1997 there have been requirements for patients to give informed consent, and to be notified if experiments were classified. The Soviet nuclear program also included medical study of exposed citizens living near Semipalatinsk Test Site, withholding information about nuclear testing or health risks. The program also involved severe radiation exposures to workers of the Mayak facility, especially the early work of forced laborers on the A-1 nuclear reactor. Criminal activity has involved murder and attempted murder carried out through abrupt victim contact with a radioactive substance such as polonium or plutonium. The death of Alexander Litvinenko is widely believed to be assassination via polonium poisoning and on the order of the Russian FSB, and polonium is also suspected as the cause of death for Yasser Arafat, Yuri Shchekochikhin, Lecha Islamov and Roman Tsepov.