Radiation can damage DNA through ionization, potentially leading to cell death or mutation and increased cancer risk; while high doses cause acute radiation syndromes like hematopoietic syndrome, even low doses slightly increase lifetime cancer risk proportional to dose; medical uses of radiation involve careful consideration of dose required versus risk to maximize benefits like cancer treatment and diagnostics using techniques like x-rays and radiotracers.

1. Biological Effects
and Risks of Ionizing Radiation

2. Objectives
I WILL :
1. Explain the basis of radiation effects.
2. Compare radiation risks with other common risks
YOU WILL:
1. Know the additional cancer risk incurred from exposure
to 25 rem.
2. Make an informed decision with respect to a personally-
acceptable emergency radiation risk.

3. Sources of Information
We can’t truly perform controlled experiments so we look at
populations that were accidentally or otherwise exposed.
Radiation exposed populations include:
Early X-ray workers
Radium Dial Painters
Hiroshima and Nagasaki Survivors
Uranium Mine Workers
Ankalosing Spondilitis
Ringworm
Accidents

4. Variation in Biological Effect
When you are interested in knowing a relationship
between radiation and injury, you would like to
know such things as:
Radiation Type
Radiation Energy
Part of Body Irradiated
Dose
Dose Rate

5. Stages in the
Biological Damage Process
Damage can be broken down
to three distinct time frames:
Physical
Chemical
Biological

6. Biological Damage
Physical Stage
• Radiation deposits energy
• Excess energy removes an electron from an
atom (ionized)
• Very quick! ~10-12 s

7. Biological Damage
Physical Stage - Ionization
Charge = 0 Charge = +1 (ion)

8. Biological Damage
Chemical Stage
• Ionized water can produce what are called
“free radicals”
• Radicals can be very reactive chemically
• The problem occurs when it reacts with
DNA
• Ionization of DNA directly can also result
in unwanted chemical reactions
• Still very quick! ~10-7 s

9. DNA

10. Biological Damage
Chemical Stage

11. Biological Damage
Biological Stage
• Biological change reveals itself when a
cell tries to replicate
• During replication, the cell reads the
DNA
• What if the DNA had been damaged?!

12. Biological Damage
Biological Stage
Several things can happen to irradiated cells:
1. Immediate death (not likely)
2. DNA damage could lead too:
- death during next division
- prevention of division
- non-fatal mutation (What?!)
3. No effect!

13. DNA Replication

14. Biological Damage
“The Big Picture”
All of these cell effects revolve around cell division.
Cells which do not divide will be resistant to radiation
damage!
The rapidly dividing cells in your body are the most
susceptible to radiation damage.
With this in mind, what tissues do you suppose are the
most sensitive to radiation?

15. Acute Radiation Syndromes
Prodromal
Hematopoietic (Blood)
Gastrointestinal
Central Nervous System

16. Prodromal Reactions
A Prodromal reaction indicates a general insult
to the body.
Can be psychosomatic, but generally indicates
that a person has received a fatal dose (+1000
rem).
Symptoms are usually seen within 30 min.
Symptoms include:
• nausea, vomiting, and diarrhea (GI)
• fatigue, listlessness, and apathy (CS)

17. Hematopoietic Syndrome
Blood cells are constantly regenerating in
your body. They have a lifetime of
approximately 30 days.
The two cell types which are particularly
important: - Platelets (clotting function)
- White Blood Cells (immune function)
This syndrome is observed at doses between
300 and 800 rads.

18. Hematopoietic Syndrome
Example

19. Gastrointestinal Syndrome
Cells which compose the lining (epithelial) of
the intestine are susceptible to radiation
damage because they are constantly dividing.
This syndrome only observed at +800 rads.
Before Chernobyl, there was only one
documented case.

20. Gastrointestinal Syndrome
Intestinal Epithelial Lining

21. Central Nervous System
Syndrome
The dose required for this syndrome is VERY high
(+5000 rads).
Essentially, the nervous system is “shorted out”
resulting in loss of various bodily functions.
Death occurs within a few days.

22. Radiosensitivity of Species
Most Least
Sensitive Sensitive
Microorganisms
Invertebrates
Plants
Fish
Amphibians
Birds
Mammals
Humans
10 100 1,000 10,000 100,000 1,000,000
Acute Dose (rad)

23. Partial Body Irradiation Effects
Testies
Temporary sterility 15 rads
Permanent sterility 500 rads
Ovaries
Sterility 500 rads
Lens
Detectable opacities 100 rads
Cataracts 500 rads
Skin
Reddening 600 rads
Blisters 1000 rads
Permanent hair loss 2000 rads

24. Problems Determining
Cancer Risk
• Why the “uncertainty”?
• There are no specific radiation induced
cancers.
• The number of people needed for such a
study would be very large.
• There is little specific information on dose.
• There is an unlimited list of confounding
factors.

25. Cancer Risk Data
Current Data from Atomic Bomb Survivors
Control Exposed Excess
Total Subjects Subjects Cancers
Number of subjects 75,991 34,272 41,719
Leukemia 202 58 144 80
All cancers except leukemia 5,734 2,443 3,291 260
Stomach 2,007 854 1,153 73
Colon 232 103 129 19
Lung 638 253 385 44
Breast 155 57 98 22
Urinary tract 133 49 84 19
Myeloma 36 13 23 7

26. Cancer Risk Data
Real data
Potential Damage
to Health
is
th es
po is
y es
H th
ar yp
o
ne
Li d
H
ol
sh
re
Th
1 rem 10 rem
Area of controversy Dose

27. Cancer Risk Coefficients
100 100
Exposed Unexposed
People People
30 25
5% Risk of
Fatal Fatal
Fatal Cancer
Cancers Cancers

28. Cancer Risk Coefficients
Based upon the Hiroshima and Nagasaki data,
the best estimate for risk is estimated by:
(Dose) × (0.0008) = Risk of developing a fatal
cancer in your lifetime

29. Cancer Risk Coefficients
Example: 25 rads
(25) × (0.0008) = 0.02
This means that I have a 2% chance of
developing a fatal cancer in my lifetime from a
25 rad dose.

30. So...
• Radiation in high doses is definitely not good for
you (>200 rads)
• Radiation in moderate doses increases your cancer
risk (5 - 200 rads)
• Radiation at doses near or below background may
(<5 rads):
do nothing
help you (maybe)

31. What You Typically Get in a Year
• Contribution of
various radiation
sources to total
average dose
equivalent to persons
in the United States
(NCRP, 1987).
• ~300 mrem

32. Range of Doses
Medical procedures
(per procedure)
• CT head and body: 110
mrem
• Chest X-ray:
• ~10-30 mrem
• Abdominal X-ray:
• ~100 mrem

33. Radiation Center Dose Info
• ALARA
• General Public
• 0.1 rem per year
• 2 mR/hr
• 5 rem Occupational
• Highest annual doses ~0.5 rem
• Typical annual dose <0.1 rem

34. How Risk is Measured
Risk = (measure of size of hazard) X (probability of occurrence)
Example:
15X106 auto accidents in the US per year
with 1 death for every 300 accidents.
Risk = (15X106 accidents/yr) X (1/300 deaths/accident)
Risk = 50,000 deaths/yr
Individual risk = 50,000/250,000,000 = 2X10-4/person/yr

35. Perceived Risk Vs. Actual Risk
Risk = (1000 accidents/yr) X (1 deaths/accident)
Risk = 1,000 deaths/yr
Risk = (1 accidents/yr) X (1,000 deaths/accident)
Risk = 1,000 deaths/yr

36. Range of Actual Risks
Deaths/person-yr Interpretation
10-2 • Disease mortality rate
10-3 • Difficult to find risks of this
magnitude
• Generally unacceptable level
• If it occurs, immediate action taken to
reduce it

37. Range of Actual Risks
Deaths/person-yr Interpretation
10-4 • People less inclined to concerted
action
• People willing to spend money to
reduce hazard
• Safety slogans show element of fear
(e.g., “The life you save may be your
own.”)

38. Range of Actual Risks
Deaths/person-yr Interpretation
10-5 • People still recognize and are
concerned about these risks
• People accept a certain level of
inconvenience to avoid risks at this
level
• Safety slogans have precautionary
ring (e.g., “Never swim alone.”,
“Keep out of reach of children.”)

39. Range of Actual Risks
Deaths/person-yr Interpretation
10-6 • Not of great concern to the average person
• Person is aware of these risks, but feels they
will not happen to him
• Phrases associated with these hazards have
an element of resignation (e.g., “An act of
God.”)
• Some feel such accidents are partly due to
stupidity (e.g., “Everyone knows you
shouldn’t stand under a tree during a
lightning storm.”)

40. Risks Which Increase the Chance of
Death by 1/1,000,000
Information taken from Physics and Society,
Vol. 19, No. 4, 1990
Activity Result
Smoking 1.4 cigarettes Cancer, heart disease
Drinking 0.5 l of wine Cirrhosis of liver
Spending 1 hr in a coal mine Black lung disease
Spending 3 hr in a coal mine Accident
Living 2 days in New York Air pollution
Traveling 6 min by canoe Accident
Traveling 10 miles by bicycle Accident
Traveling 30 miles by car Accident
Flying 1000 miles by jet Accident
Flying 6000 miles by jet Cancer from cosmic rays

41. Risks Which Increase the Chance of
Death by 1/1,000,000
Information taken from Physics and Society,
Vol. 19, No. 4, 1990
Activity Result
Living 2 months in Denver Cancer from cosmic radiation
Living 2 months if stone bldg Cancer from natural radiation
Chest X-ray taken in good hospital Cancer from radiation
Living 2 months with a smoker Cancer and heart disease
Eating 40 tblspns of peanut butter Liver cancer from aflotoxin B
Drinking Miami drinking water for 1 yr Cancer from chloroform
Drinking 30 12 oz. Cans of diet soda Cancer from saccharin
Living 5 yrs at site boundary of nuc. plant Cancer from radiation

42. Comparing the Risk

43. Comparing the Risk

44. Damage done to DNA
• DNA is made up of three parts…
• Sugar (Ribose)
• Base
• Phosphate
• The information carried in DNA is
determined by the order of the bases
• Radiation and ions from irradiation can
alter the order of the bases, therefore
causing mutation or death

45. Damage done to DNA
• When DNA is broken, the hydrogen
bonds between the bases are broken
• They will then recombine in different
orders

46. Damage Cells
• Cells that reproduce the fastest are
most effected…
• Blood
• Skin
• Reproductive
• Least or last effected are non-
reproducing cells…
• Brain
• Nervous

47. Damage Cells
• There are four types of cell damage…
• Somatic
• Genetic
• Directly
• Indirectly
• Somatic is when damage appears in
the individual exposed
• Genetic is when damage appears in
offspring

48. Damage Cells
• Direct damage is done by the radiation
itself
• Indirect damage is done by chemical
changes in the cell due to free radicals

49. Medical Uses
• Radiation is used in the medical field…
• X-rays
• Radiation Therapy
• Etc.
• X-rays are produced by hitting a
tungsten plate with electrons, then used
to expose film
• Radioisotopes can be given in pill form
or as a shot

50. Medical Uses
• The most common radioisotope used in
the medical field is Tc – 99
• Radioisotopes are chosen first by their
half-life and energy
• Next, expense and availability
• People who administer radioisotopes
are called Nuclear Medicine
Technologists

51. Lethal Dose (LD)
• The LD is what is required to kill an
individual
• It is usually listed as LD - % of death - #
of days
• For example LD – 50 – 30 tells us that
that a dose to 50% death rate in 30
days
• The change in dose and # of days,
changes the death rate