biological effects of ionizing radiation science of nuclear energy and radiation carl a. tarantino,...
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Biological Effects of Ionizing Radiation
Biological Effects of Ionizing Radiation
Science of Nuclear Energy and Radiation
Science of Nuclear Energy and Radiation
Carl A. Tarantino, CHPCorporate Health Physicist
Dominion Generation
Science Teacher WorkshopUniversity of Richmond
Richmond, VAJuly 18, 2007
Science Teacher WorkshopUniversity of Richmond
Richmond, VAJuly 18, 2007
Radon
X-Rays
ConsumerProducts
NuclearPower
RadioactiveWaste
Nuclear Medicine
Solar Radiation Cosmic Rays
TerrestrialRadiation
Food &Drink
Each Other
Radiation in LifeRadiation in Life
Ionizing Radiation UnitsIonizing Radiation Units
Old Units SI Units What It Is
1 C kg-1 = 3876 R
rad Gray
1 Gy = 100 rad
rem Sievert
1 Sv = 100 rem
Measuring Radiation EffectsMeasuring Radiation Effects
How much radiation is produced– Activity: decays per time (Curie (Ci), Becquerel (Bq))
How much energy absorbed by tissue– Dose
How much biological damage does the radiation do per energy absorbed
– Dose equivalent
Ionizing Radiation EffectsIonizing Radiation Effects
Absorption of Radiation
Ionization
Chemical Change
Repair or Damage
High Dose EffectsCell killingTissue or organ effectsWhole body effects
Low Dose EffectsMutationsCancerEffects to unborn
Cellular OrganizationCellular Organization
Potential Radiation Damage to DNA
Potential Radiation Damage to DNA
Most critical molecule within humans: DNA Direct effect
on molecule by ionization or excitation of the molecule and subsequent dissociation of the molecule
Other Damage to DNAOther Damage to DNA
Many other entities cause breaks in DNA – Temperature, chemicals, etc.
Human DNA suffer millions of DNA breaks daily– Most repaired
H2O
H2O+
e-H+
H2O2
OHo
HO2
OH-Ho
H2
WATERWATER
Radiation Induced Decomposition of Water
Within a Cell
Radiation Induced Decomposition of Water
Within a Cell
Incoming Radiation
Production of free radicals within the cell can result in indirect effects
Most abundant molecule within humans: Water
Potential Outcomes of Radiation
Damage to Parent Cells
Potential Outcomes of Radiation
Damage to Parent Cells
Cell Repair after Chronic Dose Damage
Cell Repair after Chronic Dose Damage
Time
Rad
iati
on
Dose
Accumulated Irreparable
Reparable
Cellular Radiosensitivity:Law of Bergonie and
Tribondeau
Cellular Radiosensitivity:Law of Bergonie and
Tribondeau
The basic law of Bergonie and Tribondeau is that young and rapidly dividing cells are more sensitive than cells with adult development. Cells tend to be radiosensitive if they have three properties:
»Cells that have high division rate(the time between divisions)
»Cells that have long dividing future
(immature cells in early cellular life)
»Cells that are unspecialized(cells which have a widely diverse future)
Relative Sensitivity of Cell and Tissue Types
Relative Sensitivity of Cell and Tissue Types
Lymphocytes Spermatogonia Hematopoietic (Blood
Forming) Intestinal Epithelium Skin Nerve Cells Muscle Tissue Bone Collagen
Hematological Response 1 Sv (100 rems)
Hematological Response 3 Sv (300 rems)
Possible Radiation Dose Response Curves
Possible Radiation Dose Response Curves
1- Linear (Non-Threshold)2 - Linear-Quadratic3 - Threshold4 - Supralinear
Dose (rem)
Eff
ects
Most conservative model: An increase in dose results in a proportional increase in risk
At low doses there is only a slight increase in risk that becomes proportional to dose at higher doses
There is a threshold for dose response at which lower doses do not result in increased risk
At low doses there is a higher risk that becomes proportional to dose at higher doses
Hormesis model (not shown): Low doses of radiation have a positive effect and decrease risk
HormesisHormesis
Some data indicate that low doses of radiation are beneficial
Not widely accepted– Conservative is better
But not impossible
Dose
Detr
iment
Benifi
cialRis
k
Risk TermsRisk Terms
A large dose of radiation in a short period of time
Small doses of radiation protracted over a long period of time
Health effects that occur randomly and for which the probability of the effect occurring, rather than its severity, is assumed to be a linear function of dose without threshold
Health effects which do not appear until a threshold value is exceeded and for which the severity of the effect increases with dose beyond the threshold
Effects which occur in the exposed individual
Effects which occur in the progeny of the exposed individual due to chromosome aberrations in the parent
Effects to the unborn fetus irradiated in-utero
Acute
Chronic
Stochastic
Non-stochastic
Somatic
Genetic
Teratogenic
Risk ExamplesRisk Examples
Hereditary effects Cancer (leukemia,
tumors) Erythema (skin
reddening) Cataracts Sterility Epilation (hair loss) Hematological effects
Genetic; stochastic
Somatic; stochastic
Somatic; non-stochastic
Somatic; non-stochastic
Somatic; non-stochastic
Somatic; non-stochastic
Somatic; non-stochastic
Biological Effects from Low Doses of RadiationBiological Effects from
Low Doses of Radiation
Biological effects from low doses potentially occur due to chronic exposures. A chronic exposure occurs when a relatively small amount of radiation is absorbed by tissue over a long period of time.
Under 5 rad of exposure - No detectable health effects in exposed individual
Chronic exposures result in an increased risk in latent adverse health effects
Health effects could be genetic effects or somatic effects
Latency PeriodLatency Period
Time (years)
Ris
k
Time radiation dose received
Latent period
Period at risk
Risk curve
0 4 30
Leukemia latency and time at risk periods
Latency period is the time from time of exposure until the effect is exhibited
Radiation exposure does not produce cancer in every exposed person
Effects can be immediate or years later for acute, high-level exposures
Biological effects from high doses occur due to acute exposures. An acute exposure occurs when a relatively large amount of radiation is absorbed by tissue over a short period of time; effects can occur in the short term and long term.
Biological Effects from High Doses of RadiationBiological Effects from High Doses of Radiation
Hematopoietic Syndrome: (100-200 rad or 1-2 Gray) Early symptoms are anorexia, nausea, and vomiting followed by a phase of bone marrow depression and subsequent susceptibility to infection. After several weeks, death may occur.
Gastrointestinal Syndrome: (700-1000 rad or 7-10 Gray) Early symptoms are anorexia, nausea, and vomiting followed by fever, diarrhea, and electrolyte imbalance due to ulceration of the intestinal wall. Once GI system ceases to function, death will occur.
Central Nervous System Syndrome: (2000-5000 rad or 20-50 Gray) Symptoms occur very quickly and the brain and muscles can no longer control bodily functions, including breathing and blood circulation. Death within hours or within several days.
Effects From Acute, High-level Radiation DosesEffects From Acute, High-level Radiation Doses
Dose (rad)
0 - 100 100 - 200 200 - 600 600 - 1000 1000 - 5000 Over 5000
Incidence ofVomiting
None100 rad: 5%
200 rad: 50%300 rad:
100%100% 100% 100%
Time of Onset ------ 3 hr. 2 hr. 1 hr. 30 min. 30 min.
PrincipalAffected Organs
None Hematopoietic tissueGastrointestinal
tract
Centralnervoussystem
CharacteristicSigns
NoneModerate
leukopenia
Severe leukopenia; purpura;hemorrhage; infection;epilation above 300 rad
Diarrhea; fever;disturbance of
electrolytebalance
Convulsion;tremor;ataxia;
lethargy
Critical PeriodPost Exposure
------ ------ 4 to 6 weeks 45 to 14 days 1 to 48 hrs.
Prognosis Excellent Excellent Good Guarded Hopeless Hopeless
ConvalescentPeriod
NoneSeveralWeeks
1 to 2 months Long ------ ------
Incidence ofDeath
None None0 to 80%(variable)
80 to 100%(variable)
90 to 100% 90 to 100%
Death OccursWithin
------ ------ 2 months 2 weeks 2 days
Cause of Death ------ ------ Hemorrhage; infectionCirculatory
collapse
Respiratoryfailure; brain
edema
Median Lethal Dose CurveMedian Lethal Dose Curve
Dose (rad)
LD50 - Median Lethal Dose
LD50/30 - Lethal dose to 50% of exposed population
within 30 days of irradiation, without medical attention Defined at approximately 450 rad
What is Safe?What is Safe?
Driving a car is “safe”– 1:6,000
Living at home is “safe”– Falls -- 1:20,000– Fires -- 1:50,000– Poisoning -- 1:40,000– Total -- 1:10,000
Radiation (1 mSv) is safe– 1:20,000
10.96
10.00
6.16
4.50
4.40
3.42
3.15
2.85
2.33
2.20
0.57
0 2 4 6 8 10 12
Alcoholic
Poverty
Smoking-Male
No Friends
Heart Disease
Cancer
High Risk Job
20% Overweight
H.S. Drop-Out
Orphan
Car Accidents
Years
Relative Risk:Years of Life Lost
Relative Risk:Years of Life Lost
Relative Risk:Days of Life Lost
Relative Risk:Days of Life Lost
207130
11593
7755
5050
30242322
209.3
7
0 50 100 150 200 250
Car Accidents
Alcohol
Suicide
Murder
Air Pollution
AIDS
Energy Conservation
Spouse Smoking
Radon
Drowning
Radiation Worker
Drinking Water
Fire, Burns
Natural Radiation
Natural Hazards
Days
168
148.8
144
108
60
48
24
21.6
8
3
1.2
0 20 40 60 80 100 120 140 160 180
Natural Hazards
Medical Radiation
Bicycles
Electrocution
Hazardous Waste
Nuclear Power
Peanut Butter
Milk
Live Near Nuc Plant
Broiled Steaks
Nuclear Power
Hours
Relative Risk:Hours of Life Lost
Relative Risk:Hours of Life Lost
Government
Anti-nuclear activists
Summary of Ionizing Radiation Effects
Summary of Ionizing Radiation Effects
All radiation may not be harmful– However, data does not contradict the
linear, non-threshold theory for some effects (cancer, genetic effects)
Effects from high doses are known fairly well– Depending upon dose, radiation may affect
various cells, tissues, and organs– Without medical treatment, about 50% of
people exposed to approximately 450 rad of radiation are expected to die within 1-2 months
– Acute (short-term) effects below 100 rad are relatively minor
Summary of Ionizing Radiation Effects
Summary of Ionizing Radiation Effects
Effects from low doses occur less frequently and take longer to develop than high dose effects– Studies of populations chronically exposed to
low levels of radiation have not shown conclusive evidence of increased cancer risk
– The magnitude of the risk is inferred from data at higher doses
– The lower the dose of radiation, the longer it takes for the cancer to develop
– Some changes in blood have been detected down to several rad
Summary of Ionizing Radiation Effects
Summary of Ionizing Radiation Effects
Genetic effects have not been detected in people– Genetic effects may occur, but at rates
so low that they have not been detected over the rate that occurs in the absence of radiation
The unborn child and young children appear to be more sensitive to the effects of radiation than adults are– The rate that effects occur is very low
The EndThe End