Radiation Biology, Effects and Risk Radiation Bruce Busby Radiation Safety Manager FHCRC

RadiationRadiation

Biology, Effects and RiskBiology, Effects and Risk

RadiationRadiation

Biology, Effects and RiskBiology, Effects and Risk

Bruce Busby

Radiation Safety Manager

FHCRC

Introduction

FHCRC– Seattle, WA– Cancer research – prevention and treatment– Established in 1975– Broadscope biomedical research lab– 3,000 employees, 600 radiation workers– 3 Nobel prize winners

Today’s Objective

What today's lecture will do:– Discuss Sources of Radiation– Discuss Radiation Interactions with Humans– Review Basics of Effects of Radiation – Review Risk with Examples

Our Our Basic Basic PremisePremise

Radiation PhysicsRadiation Physics

Radiation

Radiation: Energy in transit, either as particles or electromagnetic waves

Ionizing Radiation: Radiation with enough energy to cause an electron to leave an atom

4 main types– Alpha particles– Beta Particles– Neutrons– Gamma and X-ray

Gamma-Ray and Beta Decay

Gamma Rays(317 and 296 keV)

Parent NucleusIr-192

Daughter NucleusPt-192

01

Electron Capture (ε)

Orbital electron captured by nucleus Proton and electron combine Always accompanied by release of energy

The Nucleus which contains neutrons and protons

Electrons

X-Ray Production (Bremsstrahlung)

ElectronX-Ray

Target NucleusTungsten

Cathode(-)

Anode (+)

X-Rays

Gamma/X-ray Interactions

Gamma and X-ray (photons) energy causes excitation or ionization of electrons

Probability of interaction based on electron density and energy of photon – why lead and DU?

Radiation Interaction Film Exposures

Silver halide (e.g., AgBr) crystals are held in suspension throughout the film’s emulsion

Radiation ionizes some of the silver halide crystals: latent image– Br has an atomic number of 35

Each ionized crystal of silver halide can be reduced (developed) to form a grain of black metallic silver

Units of Radiation

Measure of

Amount ofradioactive material

Ionization in air

Absorbed energy per mass

Quantity

Activity

Exposure

Absorbed Dose

Dose Equivalent

Unit

curie (Ci)

roentgen (R)

rad

remPersonnel Dose

Measures of Radioactivity

The quantity of radioactive material present at a given time:

Curie (Ci) : 3.7x1010 disintegration per second (dps)

or

Becquerel (Bq): 1 dps

Roentgen (R)

Measure of exposure Charge produced in a specific

volume by gamma or x-rays 1 R = 2.58 x 10-4 C/kg SI unit is C/kg Meters (Ion Chambers and GM

detectors) often read out in mR/hr

RAD

Radiation Absorbed Dose Energy deposited per unit mass 1 rad = 100 erg/gm Does not account for different radiation

damages SI unit is the gray (Gy) 100 rad = 1 Gy

REM

Measure of Biological Damage Effective Dose Equivalent

– External or partial body dose (EDE)– Total Body Dose (TEDE) – Internal Dose (CEDE)

rad x QF = rem– QF based on differences in types of radiation

SI unit is sievert (Sv) 100 rem = 1 Sv

Good News

For x-ray, beta and gamma radiation

1 R 1 rad 1 rem

So for protection a roentgen is equal to a rem

Most instruments read out in mR/hr Dosimeters read out in mrem

Radiation Sources and Doses Radiation Sources and Doses

Sources

Natural - Sea of Radiation– Radon– Cosmic– Terrestrial

Human-produced– Nuclear Medicine– Cancer Therapy– Nuclear power

Average US Dose

Factors in Background Location, location, location

– Radon– Cosmic– Terrestrial

Flying Smoking

X-rays and nuclear medicine – Examples

Sources in Radiography

Ir-192 Co-60 X-ray Other

Ir-192

Half Life - 73.827 d Decay modes

β- 95.24%

ε 4.76% Major Gammas

– 295 keV 308 keV 316 keV – 468 keV

Made from Ir-191 (n, gamma)

Typical Radiation Doses

Flight from Los Angeles to New York 3 mremChest X-ray 10 mremAnnual public dose limit 100 mremAnnual background 360 mremFetal dose limit (gest. period) 500 mremRadiographers annual (1993 Value) 540 mremCT Scan 780 mremAnnual radworker WB dose limit 5,000 mremAcute radiation syndrome 100,000 mremLD50/60 for humans 350,000 mremRadiation therapy 1,200,000 mrem

Radiation Biology and Health Effects

Radiation Biology and Health Effects

Cells in Your Body

Trillions of cells make up the body Cells --> Tissue --> Organs -->Body Active cells are more radio-sensitive

– White blood cells, Bone marrow, Stomach lining, Hair follicles

Inactive cells are radio-insensitive– Bone, Muscle, Tendon, Nerves, Skin

Radiation Damage - Ionization

Radiation causes Ions and free radicals in cell

ex: Radiation + H20 -> OH- + H•

These free radicals and ions react with parts of the cell– attack sensitive areas– cause damage

May have direct damage to “targets” also

Damage - Cell

Most Critical Target in Cells - DNA– Damage DNA– MAY cause effects to the cell

– H2O coating is primary target

– Single breaks (SSB)– Double strand breaks (DSB)

Damaged Cells

Once Damaged, the Cell May: – Repair the damage - No problem

» Damaged cells held in cell cycle» Enzymes repairs SSB and some DSB

– Die - No problem on small basis» 1% of cells die each day» No longer working

– Mis-repair/non-repair – BAD– Too many dead cells – BAD

Health Effects

From cell to health effects Cells --> Tissue --> Organs -->Body

Effects Depends on– dose rate (Acute or Chronic)– dose– type of radiation– location of dose

Terms - Effects

Stochastic (random) – No known threshold– Cancer– Risk proportional to dose

Non-stochastic (not random)– Have threshold– Cataracts– Burns

Lets Look at the Effects

Whole Body Acute Partial Body Acute

Whole Body Chronic– Somatic– Heritable

WHOLE BODY ACUTEWHOLE BODY ACUTE

Whole body

Effects are based on sensitive tissues

Hematopoietic Syndrome (blood) Gastrointestinal Syndrome (stomach/intestines) CNS Syndrome (nerves and brain)

Early Effects Latent Effects Late Effects

Effects Based on Whole Body Dose

Dose 10 rem – no symptoms, no method of detecting outside of

dosimeters

Dose ~ 50 rem– no symptoms, minor decreases in white cells and

platelets

Dose ~ 75 rem– No symptoms in most people, decrease in white

cells

Acute Radiation Syndrome > 100 rem

Early stage

– nausea, vomiting, diarrhea and fatigue

– higher doses produce more rapid onset and greater severity

Latent period – patient appears to recover– decreases with increasing dose

Acute Radiation Syndrome Dose ~ 100 rem

– ~10% exhibit nausea and vomiting within 48 hr – mildly depressed blood counts

Dose ~ 350 rem– ~90% exhibit nausea/vomiting within 12 hr, 10% exhibit

diarrhea within 8 hr– severe bone marrow depression – ~50% mortality without supportive care

Dose ~ 500 rem– ~50% mortality with supportive care

Dose ~ 1000 rem– 90-100% mortality despite supportive care

Acute Radiation Syndrome

Dose ~ 1000 - 3000 rem - damage to GI system– severe nausea, vomiting and diarrhea (within minutes)– short latent period (days to hours)– usually fatal in days to weeks

Dose > 2,000 rem - damage to CNS– vomiting, diarrhea, confusion, severe hypotension within

minutes– collapse of cardiovascular and CNS– fatal within 24 to 72 hours

PARTIAL BODY ACUTE PARTIAL BODY ACUTE

Localized Dose

Local skin and tissue damage Beyond cellular repair rate Burns Dead tissue Late effects

Typical – hands, fingers, skin, eyes Other – thigh, rear, chest….

Localized Radiation Effects

Skin - No visible injuries < 500 rem– Prompt - erythema, epilation >600 rem– Moist desquamation >1,800 rem– Ulceration/Necrosis >2,400 rem

Eyes - Cataracts– Acute exposure >200 rem– Chronic exposure>600 rem

Permanent Sterility– Female >250 rem– Male >350 rem

Example -Acute Localized Exposure

Day 1: Estimated exposure

900 to 1,500 rem to the left hand

Performing contact exposures on pipe with no collimator.

Source was never retracted in between exposures. Using 68 curies of Ir-192 Handled the guide tube with his left hand less than

50 seconds

This radiographer was not using a survey meter (two were provided) and had no dosimetry on him during this incident.

Real Scenario – USA 2001

9 days after over exposure

9 days after over exposure

9 days after over exposure

9 days after over exposure

9 days after over exposure

9 days after over exposure

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9 days after over exposure

13 days after over exposure

13 days after over exposure

13 days after over exposure

13 days after over exposure

13 days after over exposure

13 days after over exposure

13 days after over exposure

13 days after over exposure

13 days after over exposure

19 days after over exposure

19 days after over exposure

19 days after over exposure

19 days after over exposure

19 days after over exposure

19 days after over exposure

25 days after over exposure

25 days after over exposure

25 days after over exposure

25 days after over exposure

25 days after over exposure

45 days after over exposure

45 days after over exposure

45 days after over exposure

45 days after over exposure

108 days after over exposure

108 days after over exposure

108 days after over exposure

LOOKS ARE DECEIVING The radiographer’s injuries appear to have healed over

the four months that these photographs were taken. The radiographer was in extreme pain during the blistering and healing of his hands. He had to keep his injuries covered, because air touching his hands was painful.

Over the last couple of years every winter the same blistering and healing process would occur. The pain became too unbearable for him and he had to have his first finger removed and is considering removing the thumb and second finger on his left hand removed. To this day, he has the blistering and healing occasionally happen (not as extreme) to his right hand.

Epilog

With a 100 Ci I-192 source in close contact with you, how long would it take to get

500 rem hand dose

1500 rem hand dose

20,000 rem hand dose (10 R whole body)

– 2 seconds

– 6 seconds

– 1 minute

Actions for Acute High Dose WB

Estimating the severity of rad injury is difficult.– Signs and symptoms: Rapid onset and greater severity indicate

higher doses. Can be psychosomatic.– CBC with absolute lymphocyte count– Chromosomal analysis of lymphocytes

Treat symptomatically. Prevention and management of infection is the primary objective.– Hematopoietic growth factors, e.g., GM-CSF, G-CSF (24-48 hr)

– Antibiotics/reverse isolation

– Electrolytes Seek the guidance of experts.

– Radiation Emergency Assistance Center/ Training Site (REAC/TS)

WHOLE BODY CHRONIC WHOLE BODY CHRONIC

Chronic Health Effects from Radiation

Based on damage to DNA Cancer is the major risk from low dose

radiation Cancer is also common in humans Radiation risk is low and natural occurrence

of cancer is high– Makes studying low level risk hard– Often extrapolated from high doses to low

using a linear relationship

Genetic Effects - heritable

Of the offspring and descendents of the survivors of Nagasaki and Hiroshima (>100,000 people), there have been no observable increase in the mutation rate.

The risk is still possible, though much smaller (10X) than the risk of cancer

Doubling dose in humans is 100 rem

Radiation RiskRadiation Risk

Risks

Risk is a personal choice Weighing benefit Something we do every day Needs to be informed Often bias based on bad information,

stereotypes, myths

Who Determines the Risks?

National Academy of Science– BEIR ~ every 10-15 years

United Nations– UNSCEAR

Government agencies– EPA

Other – NCRP, ICRP

What Information is Used?

Cellular Studies Animal Studies Accidents Miners Medical Exposures Human Studies Atomic Bomb Survivors

– 170,000 people with 10-400 rem doses

Dose Response Curves

Known

Risk from Low Level Radiation

BEIR VII (2005)

Estimates fatal cancer risk Estimated incidence

Fatal cancer risk ~ 6% per 100 rem (BEIR VII)– Range from 4%-10% based on methods, groups

5 rem increases the risk of fatal cancer by ~ 0.3% 25 rem increases the risk of fatal cancer by ~ 2%

BEIR VII Risk (100,000 people)

Example

Looking at 10,000 people from the US– Will have 3,000 cancers from “natural causes”– Giving this 10,000 people 10 rem

» may cause 60 additional cancers» 3,060 vice 3,000

Risk Comparisons

Radiation Risks concepts are hard to understand at low doses

Related to everyday risks– Occupational– Life choices– Medical– Background radiation

Risk - Loss of Life Expectancy Cause Life Lost (time)

Smoking 20 cigarettes a day ................. 6 yearsOverweight (by 15%) ............................ 2 yearsAlcohol consumption (U.S. average) ...... 1 yearAgricultural accidents ........................... 320 daysConstruction accidents ......................... 227 daysAuto accidents ........................................ 207 daysHome accidents ........................................ 74 daysOccupational radiation dose (1 rem/y)

from age 18-65 (47 rem total) 51 daysAll natural hazards (earthquakes, lightning, flood) ................. 7 days

One in a Million Chance of Dying

10 millirem of radiationAbout 20 days of breathing Smoking 1 cigaretteSpending 2 days in New York or BostonRock climbing for 1 1/2 minutesTraveling 6 minutes by canoe Traveling 10 miles by bicycleTraveling about 45 miles by carFlying 1000 miles by jet airplaneLiving 2 months with a cigarette smoker Eating 40 teaspoons of peanut butterEating 100 charcoal-broiled steaks

Legal Dose Limits

Occupational Exposed Workers – Whole body 5,000 mrem/yr– Skin, hands and organ 50,000 mrem/yr– Eyes 15,000 mrem/yr

Minors - 1/10 of occupational limit Public and non-radiation workers

– 100 mrem/yr

ALARA

Philosophy of keeping doses low as Reasonable

Used to reduce the risks No dose without benefit Additional controls Administrative – procedures, regulations Engineered - design Still comes down to

– Time, Distance and Shielding

Fetal Irradiation

No significant risk of adverse health effects below 10 rem

Most probable effects > 10 rem are baby-

Small head size Growth retardation. Impaired mental ability. Increased childhood cancer risk.

Over Exposure IncidentsOver Exposure Incidents

Goiânia, Brazil

1987: teletherapy head stolen

Unit dismantled, Cs-137 source capsule ruptured causing major contamination

50.9 TBq (1375 Ci) cesium-137 teletherapy machine left in abandoned clinic

Goiânia, Brazil

Exposure of large number of public:

112 000 people monitored 249 people contaminated 49 people 0.1 - 6.2 Gy 4 people died

6 y old girl 18 y old man 22 y old man 38 y old mother

Goiânia, Brazil

85 houses significantly contaminated 200 people evacuated 7 houses demolished

Goiânia, Brazil

Total volume of waste = 3500 cubic m3800 metal drums1400 metal boxes10 shipping containers

Gilan, Iran

1996: Ir-192 source used for industrial radiography falls out of shielded container

Manual worker picks up source and puts it in chest pocket

Gilan, Iran

Resulting in severe radiation

burns to the chest

Istanbul, Turkey December 1998: Two containers sold as scrap and broken open 3.3 TBq (88 Ci) cobalt-60 source unshielded Containers dumped 10 persons with acute radiation syndrome 404 persons medically examined 23.5 TBq (636 Ci) cobalt-60 source unaccounted

Samut Prakarn,Thailand

October 1999: 3 disused teletherapy sources stored by a private company at unsecured parking lot

Jan/Feb 2000 unauthorized removal of one unit - dismantled for scrap

15.7 TBq (425 Ci) cobalt-60 source unshielded 10 people highly exposed 3 of whom died no contamination

Lilo, Georgia

Lilo military training center 1997: 11 Georgian soldiers

developed radiation induced skin lesions and acute radiation syndrome

Abandoned sources (Cs-137, Co-60, Ra-226) found at various locations:

in coat pocketon building sitein buildingsburied in groundsin refuse moundon soccer field

December 2001, Lja, Georgia

A group of woodcutters find 2

hot ‘objects’ in the forest. (unshielded

strontium-90 sources,

each approx. 30,000 Ci !)

The back of patient 2 on 6 January 2002

… sources later discovered beside a path, under a rock, on the edge of a 50m-

deep 30°-slope.Source

Source

Source Recovery in Georgia

Radioisotopic Thermoelectric Generators (RTGs)

RTG’s were used in various civilian and military applications (e.g. to power navigational beacons and communications equipment in remote areas…)

Radiological Accident Statistics (1944-2000) ~ 400 reported accidents ~ 3000 exposed persons > 100 deaths, more than half involving

patients In addition, orphan sources can be mixed up

with scrap causing contamination problems Illicit trafficking involves orphan sources but

very few orphan source incidents are due to illicit trafficking events

Final Outcome

View parts of Movie if time permits

Effects of an Over Exposure Incident

Radiation Over Exposure Incidents effects more then the radiographer involved.

Incidents could over expose the assistants, site workers or even the public that are not involved with the industry.

Suspension or losing a materials license also has an economic effect on small companies that could go out of business or large companies that could face massive layoffs.

Think & Work Safe

Most (if not all) radiography over exposure incidents are 100% preventable

If you cannot perform a radiograph safely and with your full attention, don’t

More people than you would be affected by an over exposure incident

Think about having your pictures shown at next year’s training!

Summary Review

– Background radiation– Sources– Biological basis for health effects– Risks from radiation– Dose limits

Where to Get More Info

General Information – www.physics.isu.edu/radinf

State Radiation Control Office– www.doh.wa.gov/ehp/rp/

Federal Nuclear Regulatory Commission– www.nrc.gov

Contact info

Bruce Busby, CHP, RSMFred Hutchinson Cancer Research Center

bbusby@fhcrc.com

phone (206) 667-4045