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