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*





Men Women

Lung & bronchus 31% 289,550 270,100

26% Lung &

Prostate 9% bronchus

Colon & rectum 9% 15% Breast

Pancreas 6% 10% Colon & rectum

Leukemia 4% 6% Pancreas

Liver & intrahepatic 4% 6% Ovary

bile duct 4% Leukemia

Esophagus 4% 3% Non-Hodgkin

Urinary bladder 3% lymphoma

Non-Hodgkin 3% 3% Uterine corpus

lymphoma 2% Brain/ONS

Kidney 3% 2% Liver &

All other sites 24% intrahepatic bile duct

23% All other sites







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