radiation biology, effects and risk radiation bruce busby radiation safety manager fhcrc
TRANSCRIPT
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
9 days after over exposure
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
phone (206) 667-4045