About Acute Radiation Syndrome (Radiation Sickness)

What is Acute Radiation Syndrome?

Acute radiation syndrome (ARS), also known as radiation sickness or radiation poisoning, is a serious illness that occurs when a person is exposed to high levels of radiation in a short period of time. It can result from various sources such as nuclear accidents, atomic bombs, or unintentional exposure to radiation. ARS can be divided into three subtypes based on the affected body systems:

Bone marrow ARS: This is the most common type of ARS. It affects the bone marrow, where blood cells are made. This can lower infection-fighting white blood cells, red blood cells, and platelets. It can happen after lower ARS-level radiation doses. Many people recover with medical care, but recovery depends on the dose and the person’s overall health.
Gastrointestinal ARS: This type affects the stomach and intestines. It usually happens after a higher radiation dose than bone marrow ARS and can progress more quickly. Recovery is possible in some cases, but it is more difficult and often requires intensive medical care.
Cardiovascular/central nervous system ARS: This type affects the heart, blood vessels, and brain. It occurs after an extremely high radiation dose delivered over a short time. It is considered fatal, even with medical treatment.

ARS can cause severe symptoms and may be life-threatening when the radiation dose is high enough. ARS usually occurs after a person receives a large dose of penetrating radiation to the whole body, or much of the body, over a short time. The dose associated with ARS is typically greater than 0.7 gray (Gy), or 70 rads. Gray and rad are units used to measure how much radiation energy is absorbed by body tissue.

ARS can progress through four stages. The timing and severity of each stage depend mainly on the radiation dose.

Prodromal stage: Early symptoms, such as nausea, vomiting, loss of appetite, and sometimes diarrhea, may begin within minutes to days after exposure.
Latent stage: Symptoms may improve for a while, and the person may look and feel better. This stage can last from hours to weeks, depending on the dose.
Manifest illness stage: Symptoms return or worsen. The symptoms depend on which body systems are most affected, such as the bone marrow, digestive system, skin, heart and blood vessels, or brain.
Recovery or death: Some people recover over weeks to months, and recovery can take up to about two years. People with very high radiation doses may not recover and may die within days to months after exposure.

Causes and Risk Factors for Acute Radiation Syndrome

The disease causes of acute radiation syndrome (ARS) include:

Hematopoietic damage: Radiation affects the bone marrow, leading to decreased production of white blood cells, red blood cells, and platelets. This condition, called myelosuppression, increases the risk of infections and bleeding.
Gastrointestinal damage: Radiation can damage the cells lining the gastrointestinal tract, leading to symptoms such as nausea, vomiting, diarrhea, and dehydration.
Cardiovascular-central nervous system damage: In severe cases of ARS, radiation can affect the cardiovascular system and central nervous system. This can result in symptoms such as dizziness, confusion, seizures, and cardiovascular collapse.

Factors that can affect the risk of ARS include:

Radiation dose: The risk of ARS increases when a person receives a high dose of penetrating radiation over a short period of time. Higher doses are more likely to cause severe illness.
How much of the body is exposed: ARS is more likely when the whole body, or a large part of the body, is exposed. A small, localized exposure may cause injury to that area but is less likely to cause ARS.
Time near the radiation source: Spending less time near a radiation source can reduce the radiation dose a person receives.
Distance and shielding: Moving farther away from a radiation source and putting a barrier, such as walls, concrete, or other appropriate shielding, between you and the source can lower exposure.

During a radiation emergency, follow instructions from emergency officials. They may tell people to get inside, stay inside, stay tuned for updates, or take steps to remove radioactive material from the body or clothing. A healthcare professional or public health official can give advice based on the type and amount of exposure.

Acute Radiation Syndrome Symptoms

Early symptoms of acute radiation syndrome (ARS) may include:

Nausea
Vomiting
Headache
Diarrhea

These symptoms can start within minutes to days after exposure. They may last for minutes to several days and may come and go. After the early symptoms improve, a person may look and feel better for a while before becoming sick again. Later symptoms may include:

Fatigue
Loss of appetite
Fever
Seizures
Coma
Skin changes, such as swelling, itching, redness that looks like a bad sunburn, blisters, or sores
Temporary hair loss after a high radiation dose to all or part of the body

The type, timing, and severity of symptoms depend mainly on the radiation dose, how much of the body was exposed, and how quickly the exposure happened. Having these symptoms does not always mean a person has ARS, but anyone who has symptoms after a radiation emergency should seek medical attention as soon as emergency officials say it is safe.

How Acute Radiation Syndrome is Diagnosed

Diagnosing acute radiation syndrome (ARS) can be challenging because it does not cause one specific symptom or test result. Healthcare providers usually consider a person’s radiation exposure, symptoms, physical exam, and blood test results together. Common steps may include:

Exposure history: Asking where the person was, how close they were to the radiation source, how long they may have been exposed, whether shielding was present, and when symptoms began.
Physical exam: Checking vital signs and looking for signs that may point to radiation injury, such as skin redness or burns, vomiting or diarrhea, dehydration, confusion, weakness, or other nervous system symptoms.
Blood tests: Repeating complete blood count tests over time to look for changes in blood cells, especially infection-fighting white blood cells called lymphocytes. A falling lymphocyte count can help providers estimate how much radiation the person may have received.
Radiation dose estimate: Using available information, such as the person’s location during the event, time to vomiting, radiation detector or dosimeter readings if available, and specialized blood tests when needed, to estimate the dose.
Contamination check: If radioactive material may be on or in the body, trained staff may use radiation detectors and may test blood, urine, or other samples to help guide decontamination and treatment.

Other tests may be used to understand the severity of illness or to check for injury to specific organs. These may include:

Specialized radiation dose testing: In some cases, blood may be sent for tests that look for radiation-related chromosome changes. These tests can help estimate dose but may not be available right away.
Ongoing blood and chemistry tests: These can help monitor infection risk, bleeding risk, dehydration, kidney function, liver function, and electrolyte levels.
Organ-specific tests: Imaging tests, heart tests such as an electrocardiogram (EKG), or procedures such as endoscopy may be used if symptoms suggest injury to the lungs, heart, stomach, intestines, brain, or other organs.

The diagnostic approach depends on the situation, the person’s symptoms, and the resources available. During a radiation emergency, people should follow instructions from emergency officials and seek medical care when it is safe to do so.

Acute Radiation Syndrome Treatment Options

Treatment for acute radiation syndrome (ARS) depends on the radiation dose, the body systems affected, and whether radioactive material is on or inside the body. The main goals are to reduce further exposure, remove contamination when present, support the body while it heals, prevent or treat infections, manage symptoms, and help the bone marrow recover when possible. Treatment may include:

Decontamination: If radioactive material is on the skin, hair, or clothing, removing outer clothing and gently washing the skin can lower exposure and reduce the chance of spreading contamination. Trained emergency or medical staff can help with this process.
- Supportive care: Fluids, medicines for nausea and vomiting, pain control, wound and burn care, nutrition support, and close monitoring can help treat symptoms and prevent complications.
- Infection prevention and treatment: Radiation can lower white blood cell counts and weaken the immune system. Antibiotics, antiviral medicines, or antifungal medicines may be used to prevent or treat infections, depending on the person’s condition.
Bone marrow support: Medicines called colony-stimulating factors may be given to help the bone marrow make infection-fighting white blood cells. Blood or platelet transfusions may also be needed if blood counts become very low.
- Treatment for internal contamination: If radioactive material has entered the body, specific medicines may help remove or block certain radioactive materials. Examples include potassium iodide, Prussian blue, or DTPA. These medicines are only helpful for certain types of radioactive material and should be used under medical or public health guidance.
- Specialized care for severe ARS: People with severe ARS may need care in a hospital, sometimes in an intensive care unit. In selected cases, specialists may consider treatments such as stem cell transplant, but this is not common and depends on the dose, injuries, infections, and overall condition.

There is no single treatment that reverses ARS. Care is tailored to the person’s exposure, symptoms, blood test results, and other injuries. During a radiation emergency, follow instructions from emergency officials and seek medical care when it is safe to do so.

A healthcare professional can explain which treatments are appropriate and what side effects to watch for. People should not take radiation-related medicines, such as potassium iodide, unless instructed by public health officials or a healthcare professional.