Radiation Exposure


This post is part of a series developed in preparation for participation in ACEP SimWars. It contains a review of several prominent emergency medicine topics which may be relevant for board preparation. Unless otherwise cited, content is based on HippoEM videos.


  • Units
    • Gray (amount of radiation absorbed by body)
    • Sievert (toxicity associated with radiation exposure)
  • Types
    • Alpha: 0.1mm penetration, injury through ingestion
    • Beta: 1cm penetration, injury through skin or ingestion
    • Gamma: deep penetration
  • Factors
    • Time and distance (1/d2)
    • Shielding
    • Radiosensitive cells (rapidly dividing such as hematopoetic, GI)


  • Localized: epilation or burns, delayed by days
  • Internal (inhaled, ingestion)
    • Radioactive iodine: high dose results in thyroid ablation, low dose increases risk of thyroid malignancy
  • External: managed by removing clothing, soap/water shower
  • Whole body (gamma)
System Dose Time of onset Signs/Symptoms
Hematopoetic 2G 2d Pancytopenia, increased risk of infection
GI 6G Hours Nausea/vomiting, diarrhea, GI bleeding
CV/CNS 10G Minutes Shock, seizure

Key clinical features

  • Multiple affected individuals with nausea/vomiting suggests radiation exposure
  • Rapidity of onset of symptoms suggests increased dose/exposure
  • LD505G
  • Prognosis by lymphocyte count
    • ALC >1000 at 48h suggests good prognosis
    • ALC <300 at 48h suggests poor prognosis