Health Effects of Radiation

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Health Effects of Radiation
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What Radiation Affects

• Directly or indirectly, radiation affects the DNA
  in cells
• DNA controls the cells function and ability to
  reproduce

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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)

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Cell Sensitivity

• Cells most affected
• Rapidly dividing cells
• (small intestines, bone marrow, hair, fetus)
• Cells least affected
• Slowly dividing cells
• (brain, nerves)

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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

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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

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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)

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Acute Somatic Effects

• lt250 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

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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.
• gt6,000 mSv (600 rem)
• Same as above plus central nervous system
  impairment. Death within 30 days.

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Delayed Somatic Effects

• 1. Cancer solid tumors
• Increased risk
• 2. Cancer leukemia
• Increased risk
• 3. Degenerative effects
• Life shortening (not sure)

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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

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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

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Latency Period
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Cancer Risks

• Normal cancer incidence
• About 55 of US citizens get cancer
• Normal mortality
• About 25 of US citizens die from cancer

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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

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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

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Radiation Induced Cancers (continued)

• Not observed to be initiated by radiation
• Pancreas, testis, chronic lymphocytic leukemia

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Low Dose Risk

• Data are good for risks from high doses of
  radiation (gt100 mSv)
• At lower doses, the effects are masked by natural
  high incidence
• Extrapolate from high dose effects to low dose
  effects

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Possible Extrapolations
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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

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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

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Linear-Quadratic

• Leukemia seems to obey this extrapolation

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Linear - No Threshold

• If we cant 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

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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 (125,000)
• 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)

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Comparative Risks

• Normal risks we face
• Smoking (lifetime) 14
• Police officer 12500
• Agriculture industry (per year) 12600
• Vehicle accident (per year) 16000
• Falls (per year) 120,000
• Home fire (per year) 150,000
• Airplane crash (one trip) 1 1,000,000

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What is Safe?

• Driving a car is safe
• (16,000)
• Living at home is safe
• (Falls 120,000, Fires 150,000, Poisoning
  140,000 total 110,000)
• Radiation (1 mSv) is safe
• (120,000)

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Years of Life Lost
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Days of Life Lost
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Hours of Life Lost