Radiation & Health Risks

Neal M. Boucher, CNMT, CSI(ML)Radiation Safety OfficerDartmouth 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 X 1 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*

ONS=Other nervous system.Source: American Cancer Society, 2007.

Men289,550

Women270,100

26% Lung & bronchus

15% Breast10% Colon & rectum 6% Pancreas

6% Ovary 4% Leukemia

3% Non-Hodgkin lymphoma

3% Uterine corpus 2% Brain/ONS 2% Liver &

intrahepatic bile duct23% All other sites

Lung & bronchus 31%Prostate 9%Colon & rectum 9%Pancreas 6%Leukemia 4%Liver & intrahepatic 4%bile ductEsophagus 4%Urinary bladder 3% Non-Hodgkin 3% lymphoma Kidney 3%All other sites 24%

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