Health Effects of Radiation. What Radiation Affects Directly or indirectly, radiation affects the...
-
Upload
denis-willis -
Category
Documents
-
view
214 -
download
0
Transcript of Health Effects of Radiation. What Radiation Affects Directly or indirectly, radiation affects the...
Health Effects of Radiation
What Radiation Affects
Directly or indirectly, radiation affects the DNA in cells
DNA controls the cell’s function and ability to reproduce
Possible Effects
Destroy the DNAKill the cell
Damage the DNA; cell can:Repair itself (most likely)Not function or function improperlyUndergo uncontrolled division
(cancer)
Cell Sensitivity
Cells most affected:Rapidly dividing cells: (small intestines, bone marrow,
hair, fetus)
Cells least affected:Slowly dividing cells: (brain, nerves)
Category of Effects
Acute SomaticImmediate effects to the organism
receiving the dose
Delayed SomaticEffects that appear years later to
organism receiving the dose
GeneticEffects that appear in offspring
Units of Dose
Dose measured as energy absorbed per massUnits of Gray (Gy) or rad (= 0.01 Gy)
Dose equivalent accounts for different effect of different radiationsUnits of Sieverts (Sv) or rem (= 0.01 Sv)
Dose measured equated to dose equivalent1 rad roughly equals 1 rem
Dose
Average US annual radiation dose from soil, cosmic, and internal radiation0.001 Sv = 1 mSv (0.1 rem = 100
mrem
Maximum allowed annual dose for a nuclear worker0.5 Sv = 50 mSv (5 rem)
Acute Somatic Effects
<250 mSv (25 rem)No detectable effects
250 - 1,000 mSv (25 - 100 rem)Reduced red & white blood cell count
1,000 - 3,000 mSv (100 - 300 rem)Nausea, vomiting, may not be able to
fight infection
More Acute Somatic3,000 - 6,000 mSv (300 - 600 rem)More severe nausea and vomiting,
hemorrhaging, diarrhea, loss of hair, cannot fight infections, sterility. At 4,500 mSv, about half exposed will die within 30 days, others will survive.
>6,000 mSv (600 rem)Same as above plus central nervous
system impairment. Death within 30 days.
Delayed Somatic Effects
1. Cancer: solid tumorsIncreased risk
2. Cancer: leukemiaIncreased risk
3. Degenerative effectsLife shortening (not sure)
More Delayed Somatic Effects
4. Cataracts2,000 mSv single dose threshold
5. Birth defects (fetus exposed)Effects depend on time of gestation
6. Sterility2,000 mSv temporary - male8,000 mSv permanent - male
Cancer Risks
Radiation dose above 10 rem produces a small increased risk.Radiation dose does not produce cancer in every exposed personLatency period:Solid tumors: 10 - 20 yearsLeukemia: 2 - 4 years
Latency Period
Time (years)
Ris
kTime radiation dose received
Latent period
Period at risk
Risk curve
0 4 30
Leukemia Latency and Time at Risk Periods
Cancer Risks
Normal cancer incidence:About 55% of US citizens get cancer
Normal mortality:About 25% of US citizens die from
cancer
Most Common Cancers
High spontaneous incidence:Breast, lung, skin, prostate, cervix,
acute myelogenous leukemia
Moderate spontaneous incidence:Kidney & bladder, ovary, pancreas
Low spontaneous incidence:Thyroid, liver, brain, testis, bone,
chronic lymphocytic leukemia
Radiation Induced Cancers
High sensitivity to radiation:Breast, thyroid, kidney & bladder,
ovary, acute myelogenous leukemia
Moderate sensitivity to radiation:Lung, liver
Low sensitivity to radiation:Brain, bone, skin, prostate, cervix
Radiation Induced Cancers (continued)
Not observed to be initiated by radiation:Pancreas, testis, chronic lymphocytic
leukemia
Low Dose Risk
Data are good for risks from high doses of radiation (>100 mSv)At lower doses, the effects are masked by natural high incidenceExtrapolate from high dose effects to low dose effects
Possible Extrapolations
Dose
Ris
k
threshold
linear-quadratic
linear
supra-linear
Data points
Supralinear Extrapolation
Some critics claim that the risk per dose is higher at low dose that at high doseThis would mean that natural background is more harmful than high dose medical exposures
Threshold
Some effects do have a threshold dose for the effect to appearSterility, cataracts
Cancer does not seem to have a threshold, but this is not known for sure
Linear-Quadratic
Leukemia seems to obey this extrapolation
Linear - No Threshold
If we can’t see the effects, are they really there?If yes: the smallest dose may increase riskIf no: there is some level below which there is no effectControversy among radiation scientists
Cancer Risks
Increased risk of cancer mortality from 1 mSv of radiation (average annual background):Solid tumor cancer risk is about one
chance out of 25,000 (1:25,000)Leukemia risk is about one chance out
of 125,000 (1: 125,000)Total risk is about one chance out of
20,000 (1: 20,000)
Comparative Risks
“Normal” risks we face:Smoking (lifetime): 1:4Police officer: 1:2500Agriculture industry (per year): 1:2600Vehicle accident (per year): 1:6000Falls (per year): 1:20,000Home fire (per year): 1:50,000Airplane crash (one trip): 1: 1,000,000
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)
Years of Life Lost10.96
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
Days of Life Lost207
130115
9377
555050
3024232220
9.37
0 50 100 150 200 250
Car Accidents
Suicide
Air Pollution
Energy Conservation
Radon
Radiation Worker
Fire, Burns
Natural Hazards
Days
Hours of Life Lost168
148.8144
10860
482421.6
831.2
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
Government
Anti-Nukes