Things You Should Know About Radiation Exposure...But Were Afraid to Ask Jeffrey B. Nemhauser, MD Deputy Associate Director for Science Office of Public Health Preparedness and Response August 27, 2012 Centers for Disease Control and Prevention Office of Public Health Preparedness and Response Use of trade names or commercial sources is for informational purposes only and does not constitute an endorsement by the
United States Department of Health and Human Services or the US Public Health Service. Views and opinions expressed by Dr. Nemhauser are not necessarily those of the Centers for Disease Control and Prevention. Radiation is a ToxicantSort of Photons pass directly through the body; particles must be ingested/inhaled No volume of distribution
Not metabolized by biological processes Cannot be excreted Time/distance/ shielding are the means of limiting radiation exposure RADIATION Have to be ingested/inhaled to exert an effect Have a volume of distribution
Are metabolized or undergo detoxification Excretion can be facilitated Uptake can be blocked Metabolism may depend on genetic polymorphisms TOXINS & TOXICANTS Radiation is a ToxicantSort of The dose makes the poison
RADIATION TOXINS & TOXICANTS Where Physics and Biology Collide Absorbed dose Energy actually deposited from any kind of radiation in any kind of material as the radiation passes
through it rad = 100 ergs per gram of tissue SI Unit: gray (Gy) 1 joule per kilogram of tissue 1 Gy = 100 rad Louis Harold Gray Father of Radiobiology Where Physics and Biology Collide
Dose equivalent Allows for different biological effectiveness of different kinds of radiation rem is used when absorbed dose calculated in rad SI unit: sievert (Sv) used when absorbed dose calculated in Gy 1 Sv = 100 rem Rolf Sievert
Where Physics and Biology Collide rad: radiation absorbed dose Amount of energy absorbed by a given mass of tissue (ergs/gram) rem: roentgen equivalent in man Takes into account the biological effect of various types of radiation
Where Physics and Biology Collide rem = rad x RBE* Relative Biological Effectiveness RBE 1.0 for , , and x-radiation RBE 2.0 for neutrons RBE 20 for alpha particles The Law of Bergoni and Tribondeau (1906) Actively proliferating cells are the most
sensitive to the effects of radiation The degree of differentiation of cells is inversely related to their radiosensitivity Radiosensitivity of cells is proportional to the duration of mitotic and developmental activity they must pass through Cellular Radiosensitivity
Most Lymphocytes Immature hematopoietic cells Intestinal epithelium Spermatogonia & ovarian follicular cells Least Mature red cells Muscle cells Mature connective tissue, bone, cartilage
Ganglion cells Acute Radiation Syndrome (ARS) Radiation dose must be high Radiation must be penetrating (i.e., able to reach internal organs)
Radiation must be delivered over a short period of time (usually minutes) Exposure area: whole body or significant partial body Most dire acute outcome of whole body, high dose, radiation exposure The Four Stages of ARS
Prodrome Begins after exposure Lasts 2448 hours More rapid symptom onset implies greater absorbed dose Onset of prodromal adverse health effects occurs more rapidly with more severe ARS than with more mild ARS Latency Period (quiescent phase) Variable length depending on absorbed dose
Manifest Illness Recovery or Death ARS Prodrome Signs and Symptoms Nausea/vomiting Hallmark finding but not always present Time to vomiting may be used Fever
Fatigue Headache Salivary gland as rough estimate of exposure inflammation and ultimate outcome (hyperamylasemia) Diarrhea (indicator of poor prognosis) Skin erythema
ARS Prodrome Signs and Symptoms * Nicholas Dainiak, Course: Response to and Management of a Radiological Crisis, Figure 2, New York School of Medicine Courses Online. (Site registration required.) ARS Prodrome Early Markers * Adapted from lecture by Col. William Dickerson, AFRRI. ARS Prodrome Early Markers Lymphocytes Highly radiosensitive Progressive decline in
absolute lymphocyte count provides early estimate of injury and outcome Absolute Lymphocyte Count The Three Subsyndromes of ARS Hematopoietic (Bone Marrow): 250-500 rad/ 2.5-5 Gy
* Dr. William Dickerson, (AFRRI) based on Figure 6 from Vorobiev AI. Acute Radiation Disease and Biologic Dosimetry in 1993. Stem Cells 1997;15(Suppl 2):269-274 The Three Subsyndromes of ARS GI: 1000 rad/10 Gy * Hill G R et al. Blood 1997;90:3204-3213 The Subsyndromes of ARS
Neurovascular: 10,000 rad/100 Gy Death within 24-48 hours Exact and immediate cause of death unknown Endothelial destruction resulting in profound capillary leak Treatment of ARS
Largely limited to BM subsyndrome Supportive Care Colony Stimulating Factors (Neupogen/filgrastim) Antibiotics/antifungals Reverse isolation Bone Marrow Transplant * Citations, references, and credits Myriad Pro, 11pt http://remm.nlm.gov For more information please contact Centers for Disease Control
and Prevention 1600 Clifton Road NE, Atlanta, GA 30333 Telephone, 1-800-CDC-INFO (232-4636)/TTY: 1-888-232-6348 E-mail: [email protected] Web: www.cdc.gov The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.
