Radiation Risk

Radiation & Health Risks Neal M. Boucher, CNMT, CSI(ML) Radiation Safety Officer Dartmouth Hitchcock Medical Center History of Exposure         Pioneer Radiologists Atomic Bomb Survivors Radium Dial Painters Uranium Miners Medical Irradiation Animal Studies Criticality Accidents Chernobyl We know more about Radiation & its effects than any other agent        Research tool Medicine Dx & Rx Military weapons Industry precision gauges Irradiator sterilizer Accidents The accumulated knowledge is immense Uncertainties          Natural Background Other carcinogens, mutagens Genetic predisposition Thresholds Precise dosimetry Clean data Adequate follow up Long time lines Other health issues The Numbers Game  How much is dangerous?  Deterministic/somatic effects  Stochastic effects Radiation Types & Origin  X-rays from atom outer shells  e- transitions  Gamma rays from nuclear decay  Higher E photons  Beta particles wide E range  e- and e+ ejections from nucleus  Alpha particles stripped He+2  Very Energetic MeV short range Quality Factors  Damage Coefficient  Relative Biological Effectiveness  Ave weighting factors Rad X QF = Rem  Gamma & X rays X 1  Beta X1  Alpha X 20  Neutrons X 20 Radiation Biology  Interaction with matter/tissue  Ionization path LET > free radicals  Absorption tolerance / Tissue sensitivity  Cell damage  No effect  Repairable damage, free radicals  Dysfunctional proteins, enzymes, hormones  Cell death by DNA or cellular function Radiation Biology  Genetic Effects  Somatic cells precancerous  Congenital defects during organogenesis  Stem cell disruption  Germ Cells     Cell Death early in Meiosis Genetic defect passed on Expression early, late, next generation Dominant /recessive Deterministic Effects       LD50/30 (Lethal Dose 50%/30 days) RAD/REM definition WB systemic vs local irradiation Acute vs chronic exposures Minimum detectable response GSD Genetically Significant Dose Symptoms of acute exposure Onset within minutes to hours Psychological effect Blood Counts, lymph platelets Gastro-Intestinal Synfdrome 300-500 Rad Neuro-Vascular Syndrome >1000 Rad Central Nervous Sys. shutdown 10,000 Rad Untreated, aplastic anemia, infection 30 days 500 Rad LD 50/30  Dermal effects if localized        Low Level Cancer Induction  Where’s the data?  How does it translate to occupational exposures?  What are the odds compared to natural background radiation?  What impact does Medical exposure have?  What about longevity? Dose Effect Models The Odds        1 mRem of exposure ^ risk by 1 in 106 Natural Background (NH) 350 mRem 1 Chest film PA & Lat 25 mRem 1 CT Scan 3000 mRem 1 Mammogram 10 mRem Trans-Atlantic flight 35K ft 1 mRem/hr Normal fatal CA incidence 1 in 7 2007 Estimated US Cancer Deaths* Lung & bronchus Prostate Colon & rectum Pancreas Leukemia Liver & intrahepatic bile duct Esophagus Urinary bladder Non-Hodgkin lymphoma Kidney All other sites 31% 9% 9% 6% 4% 4% 4% 3% 3% Men 289,550 Women 270,100 3% 24% Lung & bronchus 15% Breast 10% Colon & rectum 6% Pancreas 6% Ovary 4% Leukemia 3% Non-Hodgkin lymphoma 3% Uterine corpus 2% Brain/ONS 2% Liver & intrahepatic bile duct 23% All other sites 26% ONS=Other nervous system. Source: American Cancer Society, 2007. Bone Cancer  Radium Dial Painters c 1920-50  First epidemiological study linking radioactive material to cancer  Discovered by high incidence of anemia and bone cancers of the jaw Leukemia  Most sensitive indicator  Only shows up statistically after large doses  Other Causes     Benzene, formaldehye Chemo Rx alkylating agents Downs Syn & other genetic disease Human T-cell Virus & Myelodysplastic Dis. The Case of I-131 Therapy First radionuclide widely used Long history circa 1940 Activity 30-200 mCi WB dose 15 Rem Thyroid dose 30-40,000 Rads No increase in head & neck Ca’s subsequent to treatments  Why?       I-131 fallout Principal Fission fragment Easily ingested and inhaled Long half life @ 8.02 days Food chain contaminant Children and pregnant women vulnerable to thyroid uptake  Stable Iodine can block uptake       Widely debated public health issue Radiation Hormesis  European spas and natural springs  Uranium, Thorium, Radium, Radon Gas  Patent medicines prior to 1920  Immune system stimulation @ 5 Rem  Diagnostic studies  Long Term studies of Survivors  Cancer statistics are less than expected Fetal Effects of Radiation     Embryonic death Teratogen Mutagen Carcinogen Fetal Rat Study  400 Rad during gestation LD 50/30 Growth Stunting  150 Rad @ 13 days gestation