Transcript Document

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 DNA
Kill the cell
Damage the DNA; cell can:
Repair itself (most likely)
Not function or function improperly
Undergo 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 Somatic
Immediate effects to the organism
receiving the dose
Delayed Somatic
Effects that appear years later to organism
receiving the dose
Genetic
Effects that appear in offspring
Units of Dose
Dose measured as energy absorbed per
mass
Units of Gray (Gy) or rad (= 0.01 Gy)
Dose equivalent accounts for different
effect of different radiations
Units of Sieverts (Sv) or rem (= 0.01 Sv)
Dose measured equated to dose
equivalent
1 rad roughly equals 1 rem
Dose
Average US annual radiation dose from
soil, cosmic, and internal radiation
0.001 Sv = 1 mSv (0.1 rem = 100 mrem
Maximum allowed annual dose for a
nuclear worker
0.5 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 Somatic
3,000 - 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 tumors
Increased risk
2. Cancer: leukemia
Increased risk
3. Degenerative effects
Life shortening (not sure)
More Delayed Somatic
Effects
4. Cataracts
2,000 mSv single dose threshold
5. Birth defects (fetus exposed)
Effects depend on time of gestation
6. Sterility
2,000 mSv temporary - male
8,000 mSv permanent - male
Cancer Risks
Radiation dose above 10 rem produces
a small increased risk.
Radiation dose does not produce
cancer in every exposed person
Latency period:
Solid tumors: 10 - 20 years
Leukemia: 2 - 4 years
Latency Period
Time radiation dose received
Latent period
Period at risk
Risk
Risk curve
0
4
30
Time (years)
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 incidence
Extrapolate from high dose effects to
low dose effects
Possible Extrapolations
Risk
supra-linear
Data poin ts
linear
linear-quadratic
threshold
Dose
Supralinear Extrapolation
Some critics claim that the risk per dose
is higher at low dose that at high dose
This 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 appear
Sterility, 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
risk
If no: there is some level below which
there is no effect
Controversy 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): 1:4
Police officer: 1:2500
Agriculture industry (per year): 1:2600
Vehicle accident (per year): 1:6000
Falls (per year): 1:20,000
Home fire (per year): 1:50,000
Airplane 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 Lost
10.96
Alcoholic
10.00
Poverty
6.16
Smoking-Male
4.50
No Friends
4.40
Heart Disease
3.42
Cancer
3.15
High Risk Job
2.85
20% Overweight
2.33
H.S. Drop-Out
2.20
Orphan
0.57
Car Accidents
0
2
4
6
Years
8
10
12
Days of Life Lost
207
Car Accidents
130
115
Suicide
93
77
Air Pollution
55
50
50
Energy Conservation
30
24
23
22
20
Radon
Radiation Worker
Fire, Burns
9.3
7
Natural Hazards
0
50
100
150
Days
200
250
Hours of Life Lost
168
Natural Hazards
148.8
144
Medical Radiation
Bicycles
108
Electrocution
60
Hazardous Waste
Anti-Nukes
48
Nuclear Power
24
21.6
Peanut Butter
Milk
Live Near Nuc Plant
8
Broiled Steaks
3
1.2
Nuclear Power
0
Government
20
40
60
80
100
Hours
120
140
160
180