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Radiation sickness

Definition :
Radiation sickness is illness that occurs from exposure to a large amount of radiation. The exposure may be in a series of doses over time (chronic) or in a single large dose (acute).

Exposure to large doses of radiation can cause severe illness, and in some cases, death. The larger the dose, the greater your risk of cancer and other adverse health effects, including cataracts and mental retardation in children whose mothers were exposed during pregnancy.

Causes of radiation exposure may be accidental or intentional. Intentional sources of radiation exposure could occur if terrorists blew up a nuclear power plant, set off a nuclear bomb or detonated a so-called dirty bomb. A dirty bomb uses conventional explosives to spread radioactive materials, such as radioactive waste from a nuclear power plant or sources of radiation from a medical facility.

Radiation also occurs naturally in the environment, so everyone is exposed to some daily radiation without harmful consequences. Routine cases of exposure to artificial radiation — living near a nuclear power plant or undergoing medical tests, such as an X-ray — generally occur in amounts too small to cause any damage.

Treatment for radiation sickness is designed to relieve the signs and symptoms.

The two main types of radiation are :

  • Penetrating (ionizing) radiation. Penetrating radiation affects you by entering your body and depositing high energy into your tissues, which then can cause cell damage or cell death. A large dose of penetrating radiation may kill bone marrow cells.
  • Nonpenetrating (nonionizing) radiation. Nonpenetrating radiation doesn't pass through your skin. A large dose of nonpenetrating radiation may burn your skin similar to the way severe sunburn does.

Chronic vs. acute
Exposure to large doses of ionizing radiation causes radiation sickness. The condition can be chronic or acute :

  • Chronic radiation sickness. Chronic radiation sickness may take several days or weeks to develop. The cause can be radioactive fallout from a nuclear explosion or an industrial accident. Therapeutic radiation treatments for cancer also can cause temporary chronic radiation sickness.
  • Acute radiation sickness. Acute radiation sickness can develop quickly. A person with acute radiation sickness usually has been exposed to large amounts of radiation over a brief period of time, such as in the case of an industrial accident or a nuclear bomb explosion.

Routes of exposure
Exposure to radioactivity occurs through three main routes. The route by which you come in contact with radioactivity is important because each pathway results in radiation exposure to different parts of your body. Routes of exposure include :

  • Inhalation. Radiation exposure by inhalation occurs when you breathe radioactive material into your lungs. Radioactive particles can lodge in your lungs and remain there for an extended time. As long as these particles remain and continue to decay in your lungs, radiation exposure continues. Although inhaled radioactivity is not likely to result in radiation sickness, tissue damage from inhaled radioactivity eventually can lead to a higher risk of cancer or other diseases.

    The main sources of inhaled radiation include radon gas and radioactively contaminated dust or smoke. Explosion of a dirty bomb — a bomb that uses dynamite to scatter radioactive dust, smoke or other bits of material — might cause inhaled radiation exposure, in addition to injuries caused by the explosion itself.

  • Ingestion. Exposure to radiation by way of ingestion occurs when you swallow radioactive material. This pathway of exposure releases high energy directly to your tissues, causing cell damage. Although ingested radioactivity isn't likely to result in radiation sickness, tissue damage from ingested radioactivity can eventually lead to a higher risk of cancer. Sources of ingested radiation include contaminated drinking water, plants, milk, fish and meat. Radiation doses from these sources usually are extremely small.
  • Direct (external) exposure. This route of exposure occurs from a source beaming out and striking your body. Examples of direct exposure include radiation treatments for cancer and radiation from an industrial accident or nuclear explosion, such as an atomic bomb.

Types of radiation
Types of radiation vary in the ability to damage different kinds of body tissues. These types include :

  • Alpha particles. The least penetrating form of radiation, these can't penetrate the outer layer of your skin, but they may be a risk if you have open wounds or if you ingest the radioactive source of the alpha particles.
  • Beta particles. These can burn your skin and damage your eyes.
  • Gamma rays. The most penetrating kind of radiation, these can travel long distances and penetrate your body.

Measuring radiation exposure
To measure radiation exposure, doctors and scientists use units called rem and millirem (one thousandth of a rem). According to the Environmental Protection Agency, the average American receives a dose of about 360 millirem of radiation each year. Most of that exposure comes from natural sources, such as radon gas and radiation from outer space, rocks and soil. The remaining exposure comes from artificial radiation sources, including medical X-rays.

The dose of radiation from most X-ray procedures is less than 1 rem. In comparison, the average dose of radiation received by survivors of one of the two atomic bomb explosions in Japan was as high as several hundred rems.

A single exposure of less than 50 rem — much higher than the average annual exposure — produces few observable signs and symptoms. Vomiting, fatigue and loss of appetite can accompany exposures of 50 to 200 rem, with recovery taking a few weeks. Severe changes in blood cells and hemorrhaging occur with exposures of more than 200 rem. In exposures of more than 450 rem, severe impairment of the body's ability to fight infection occurs, resulting in death about half the time.

Risk Factors:
You can be exposed to radiation anywhere that radiation sources or radioactive materials are used, such as in nuclear power plants, medical centers, research laboratories or mines where radioactive materials are removed.

The amount of radiation from these sources is small and doesn't cause radiation sickness. However, the detonation of a nuclear weapon or radiological device, such as a dirty bomb, may release harmful amounts of radiation.

When to seek medical advice :
If you or someone you know has been exposed to a large dose of radiation or a large amount of radioactive material, seek emergency medical treatment.

Evacuate the area of exposure. Remove all exposed clothing and seal it in a plastic bag, if available. If possible, wash your body and hair thoroughly with soap and water to remove any remaining radioactive material. Dry and wrap the affected areas with a towel or blanket until emergency medical assistance arrives.

Symptoms :
The signs and symptoms of radiation sickness may include :

  • Nausea and vomiting
  • Diarrhea
  • Skin burns (radiodermatitis)
  • Weakness
  • Fatigue
  • Loss of appetite
  • Fainting
  • Dehydration
  • Inflammation (swelling, redness or tenderness) of tissues
  • Bleeding from your nose, mouth, gums or rectum
  • Low red blood cell count (anemia)
  • Hair loss
The signs and symptoms of radiation sickness and their severity depend on how much radiation you receive and which tissues are exposed. The way in which you receive radiation — by breathing in radioactive material, by ingesting it with food or water, or by being exposed to intense beams of radiation — also has an effect on the signs and symptoms of radiation sickness.

If you may have been exposed to large amounts of radiation, your doctor will record your physical signs and symptoms and take a complete blood count (CBC).

A complete blood count measures the amount of hemoglobin, which determines the oxygen-carrying capacity of your blood, the percentage of red blood cells, the number and type of white blood cells, and the number of platelets. Red blood cells are the oxygen-carrying blood cells; white blood cells are the infection-fighting blood cells; and platelets help your blood clot to prevent and control bleeding.

A CBC can help detect the presence of many conditions, including anemia, infections and leukemia. You'll need frequent monitoring of your blood samples.

Determining how much exposure
In addition to physical examination and laboratory testing, doctors consider three main factors in determining how much radiation a person has been exposed to. These include :

  • Time. The amount of radiation exposure varies with the time spent near a source of radiation. When a person is assessed for radiation exposure, doctors consider the amount of time he or she has likely spent in the area of the radiation source.
  • Distance. The farther you are from a source of radiation, the less your exposure.
  • Shielding. The greater the shielding around a radiation source, the smaller the exposure. Shielding occurs when there's something that absorbs radiation between you and the source. The amount of shielding required to protect against different kinds of radiation depends on the type and the energy of the radiation.

The amount of radiation exposure someone might receive from the explosion of a dirty bomb would depend on the type and amount of the radioactive material used, as well as the variables of time, distance and shielding. Radiation experts from the Centers for Disease Control and Prevention believe that most dirty bombs wouldn't be able to release levels of radiation high enough to cause immediate serious illness, except for people in very close proximity to the explosion.

Complications :
Large doses of radiation can cause extensive damage to your cells and result in cell death. For example, radiation therapy uses relatively large doses of radiation to kill cells in tumors. But in the process of killing cancer cells, other cells may be damaged, increasing your risk of developing cancer later.

The extent of cellular damage depends on the total amount of energy absorbed, the time period and dose rate of exposure, the particular organs exposed, and the amount of cellular repair. Advances in technology have made current radiation therapy more sophisticated and precise, which results in less damage to normal cells. Healthy cells can repair most of the damage caused by small doses of radiation.

Complications of radiation sickness vary depending on the type of exposure :

  • Acute exposure. In most cases, a large single dose of radiation can cause both immediate and delayed effects. Acute exposure, if large enough, can cause rapid development of radiation sickness that may include bone marrow damage, gastrointestinal disorders, bacterial infections, hemorrhaging, anemia and loss of body fluids. Delayed effects can include cataracts, temporary infertility and cancer. Extremely high levels of acute radiation exposure can result in death within a few hours, days or weeks depending on the dose.
  • Chronic exposure. Chronic radiation exposure often produces effects that can be observed within weeks after the initial exposure. But signs and symptoms of chronic radiation exposure may not show up until years later, or they may not develop at all. Chronic exposure may increase your risk of cancer, precancerous lesions, benign tumors, cataracts, skin changes and congenital defects.

No treatment can reverse the effects of radiation exposure. Treatment for radiation sickness is designed to help relieve its signs and symptoms.

Doctors may use anti-nausea drugs and painkillers to relieve some signs and symptoms, and use antibiotics to fight off secondary infection. You may need blood transfusions if you develop anemia.

Drugs approved by the Food and Drug Administration (FDA) for treatment of radiation contamination from an industrial accident or a dirty bomb include Radiogardase, pentetate calcium trisodium (Ca-DTPA) and pentetate zinc trisodium (Zn-DTPA).

These drugs are included in the national stockpile of products for use in the event of an emergency. Radiogardase, also known as Prussian blue, may be used to treat people exposed to radiation containing harmful amounts of cesium-137 or thallium. Ca-DTPA and Zn-DTPA may be used for contamination with radioactive forms of plutonium, americium and curium. All three drugs work to eliminate the radioactive substances from your body.

Another drug that may be helpful in cases of exposure to high doses of radiation is filgrastim (Neupogen), a drug currently used in people who've received chemotherapy or radiation therapy. The drug stimulates the growth of white blood cells and can help repair bone marrow damage.

If the cause of radiation exposure or contamination is unknown or consists of more than one source, multiple drugs can be used together to prevent or treat radiation sickness.

Long-term monitoring
If you've been exposed to high amounts of radiation, you'll need long-term monitoring. Even if you recover initially, other health problems may develop months or years after exposure. You'll need regular physical examinations and laboratory studies to detect the development of delayed effects.

Avoiding exposure to large amounts of radiation is the only way to prevent radiation sickness. The condition develops only after you've been exposed to extremely high doses of radiation, such as by an industrial accident, nuclear weapon detonation or explosion of a dirty bomb.

Potassium iodide
Heightened concerns about national security have focused attention on nuclear power plants in the United States. The FDA has approved the use and over-the-counter sale of potassium iodide (KI) to protect people from thyroid cancer caused by radioactive iodine (iodine 131), a substance that can be released in nuclear explosions.

Taken just before or immediately after exposure to nuclear fallout, KI protects your thyroid gland from radioactive iodine. The protective effect of KI lasts about 24 hours, and the dose is repeated daily as long as there's risk of exposure. Children are more at risk than adults are from exposure to radioactive iodine. KI is safe and effective for even very young children when taken in the proper dosage.

Current federal government guidelines recommend that people within 10 miles of nuclear power plants be provided with KI tablets. However, KI doesn't protect other organs and tissues from absorbing radiation. It also doesn't prevent external exposure to radiation or the absorption of other radioactive substances.

In 2002, federal agencies in Washington began stockpiling KI in case of a nuclear event. However, experts believe an attack with a dirty bomb would release radioactive substances other than radioactive iodine. KI helps protect only against the effects of radioactive iodine, not other radioactive substances.

Short-term side effects of KI pills, which are more common in adults than in children, include intestinal problems, allergic reactions and minor rashes. Don't take KI if you have multinodular goiter, Graves' disease or autoimmune thyroiditis.

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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