Radiation Sickness — Symptoms and Response

Acute Radiation Syndrome (ARS), commonly called radiation sickness, occurs when the body receives a high dose of ionising radiation in a short period. It is not an immediate risk for most people from a dirty bomb at typical distances, but it is a significant concern for those close to a nuclear detonation or a high-intensity radiological source.

Understanding what causes radiation sickness, how to recognise it, and what supportive care is available helps you respond appropriately to both confirmed cases and worried-but-unaffected people (who are far more common after radiological incidents).

What Causes Radiation Sickness

Radiation sickness requires a significant dose of ionising radiation received within a short window:

Dose (Gray / Gy)	Likely Effect
Under 0.1 Gy	No observable immediate effects
0.1–1 Gy	Mild symptoms possible; usually full recovery
1–2 Gy	Mild ARS in most people; some require medical support
2–6 Gy	Moderate to severe ARS; significant medical intervention needed
6–8 Gy	Severe ARS; survival possible with intensive medical care
Above 8 Gy	Generally lethal without extreme medical intervention

Most people near a typical dirty bomb do not receive doses approaching 1 Gy. Radiation sickness from a dirty bomb is mainly a risk for those very close to the radioactive source itself.

Nuclear detonation survivors within a few kilometres of ground zero may receive doses sufficient to cause ARS.

The Four Phases of ARS

1. Prodromal Phase (Hours 0–2 After Exposure)

Early symptoms appear within minutes to hours for high doses:

• Nausea and vomiting — the earliest and most reliable indicator
• Diarrhoea (at higher doses)
• Headache
• Fatigue
• Fever

The severity and speed of onset correlates with dose: Vomiting within 30 minutes suggests a very high dose; vomiting after 2–4 hours suggests a moderate dose.

2. Latent Phase (Days to Weeks)

A period of apparent recovery follows the prodromal phase — the person may feel and look better. This is deceptive. Damage to bone marrow and other tissues is occurring invisibly.

Duration ranges from days (high dose) to weeks (lower dose).

3. Manifest Illness Phase

Symptoms return as radiation-damaged systems fail:

System	Symptoms
Haematopoietic (bone marrow)	Infection (from low white cells); bleeding (from low platelets); anaemia
Gastrointestinal (very high dose)	Severe diarrhoea; nausea; vomiting; intestinal bleeding
Neurovascular (extremely high dose)	Confusion; loss of consciousness; cardiovascular collapse

4. Recovery or Death

At doses below approximately 6 Gy with good medical support, most people recover over weeks to months. Above this threshold, survival depends on intensive haematological support (blood transfusions, possibly bone marrow transplant).

Recognising ARS in a Civilian Setting

In the aftermath of a radiological event:

1. Vomiting within 4 hours of exposure is the most actionable early indicator — these individuals need medical evaluation for potential ARS.
2. A person who does not vomit within 4–6 hours of a potential exposure is unlikely to have received a significantly injurious dose.
3. Record when vomiting first occurred — this information directly informs medical assessment of dose.

⚠️ Many people in radiological emergencies experience vomiting and nausea from psychological stress rather than radiation exposure. This does not mean their symptoms should be dismissed — it means that early medical assessment is required to distinguish psychological responses from actual ARS.

Supportive Care in a Civilian Setting

Professional treatment for ARS includes growth factors, antibiotics, blood transfusions, and in some cases bone marrow transplants — none of which are available in civilian settings without hospitals.

What you can do:

1. Evacuate to medical care — ARS cannot be effectively treated outside a medical facility. Rapid transport to hospital is the priority.
2. Treat wounds — radiation injury impairs healing; wounds need early and careful management.
3. Prevent infection — handwashing; wound protection; limit exposure to ill contacts. The immune-compromised ARS patient is vulnerable to infection.
4. Support hydration — severe vomiting and diarrhoea cause dehydration. Oral rehydration salts if the patient can drink.
5. Pain management — over-the-counter pain relief for fever and discomfort.
6. Do not give aspirin — this affects platelet function; use paracetamol/acetaminophen instead.

Potassium Iodide (KI) — What It Does and Does Not Do

KI protects the thyroid gland from absorbing radioactive iodine specifically:

• It does NOT prevent radiation sickness from other radioisotopes
• It does NOT reduce dose from external radiation sources
• It IS useful for nuclear detonations and certain reactor accidents where radioactive iodine (I-131) is released

Take KI only when directed by authorities and following age-appropriate dosing instructions.

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Quick Reference

Indicator	Meaning
Vomiting within 30 min of exposure	High dose — urgent medical evacuation
Vomiting within 1–4 hours	Moderate dose — medical evaluation needed
No vomiting within 6 hours	Likely low dose — monitor; medical follow-up
Latent (feeling better after initial symptoms)	ARS process continuing — do not assume recovery
Fever + infection signs during recovery	Bone marrow suppression — needs antibiotics
Civilian support	Hydration; wound care; paracetamol; prevent infection; hospital ASAP
KI	Only for radioactive iodine release — not for all radiation types