Lecture note 6

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19 Jul 2010

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EESA10 Lecture 6
Radiation and Human Health
Slide 1 – Radiation and Human Health
Radiation is everywhere, all around us. We cannot escape radiation. But the
question is what type and how much radiation is there.
Even if we are walking outside in the woods, we are still exposed to some radiation,
because of Background Radiation: Something that is produced and emitted from
outer space. Natural radioactivity in the earth and by cosmic rays from outer space.
This type of radiation cannot be controlled. We are always exposed to it. It has
existed for hundreds of thousands of years.
Something that we can control is man made radiation (Electronic devices,
appliances, etc.). (Note: Nowadays, engineers have found technologies to protect us
from most of this radiation). Examples of some man-made devices that emit
different types of radiation include:
- X-ray machines (different kind of equipment used in labs for analysis, for
example, CCA can also be detected using X-ray)
- X-ray Diagnostic (X-ray used for diagnostic of different body parts)
- Television sets
- Microwave ovens
- Lasers
Slide 2 – Ionizing radiation exposure to the public
Natural radiation sources consists of 82% of total measurable radiation
Man-made radiation is just 18%. Medical x-rays, nuclear medicine can treat some
illnesses and some other types of radiation. What is surprising is that Radon (gas in
indoor air) makes up 55% of total radiation.
Slide 3 – Radiation and Human Health
We have two big groups of radiation:
1) Ionized Radiation (Cosmic, Gamma, X-rays): This is radiation that has so much
energy that can change atoms on some other chemicals. They can push electrons out
of their atoms and produce ionized form of that element. They are very strong as
they have so much energy. (Note: On electric spectrum, elements that are very high
in energy have short wavelength, elements with low energy (non-ionized) have long
2) Non-Ionized Radiation (Radio waves, TV waves, Microwaves): This type does
not have enough energy (low in energy) and they cannot remove electrons from
Slide 4 – Ionized Radiation
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Affect of this radiation is obvious. All scientists agree that this radiation is really
harmful. How does it affect human health? First, the radioactive material (like
Uranium), decays naturally and spontaneously, and produces ionizing radiation.
This ion radiation, strips away electrons from atoms (create two charged ions)
It can also break some chemical bonds. This is important for human body as it
consists of water and chemicals. Examples: alpha, beta particles, gamma and x-rays.
These examples differ based on the amounts of energy they have.
Slide 5 - Health effects from exposure to radionuclides
There are 2 different kinds of health effects.
1) Stochastic effectHumans exposed to long term, lower level of radiation. This is most
problematic because it is very hard to detect and to know what will happen to our health
after long time exposure to lower level of radiation. Hard to detect and not 100% known.
What is known is that if the amount of radiation increases the severity of this affect will
not change and will stay the same and the type of illnesses will be the same. But the risk
to get that illness will increase. Risk of getting cancer will be higher. This amount of
radiation is proven to cause cancer. 2 effects associated with this Stochastic:
! Cancer is uncontrolled growth of cells (any kinds of cells as there are many kinds of
cancers). Naturally in our physiological functions, our cells divide and produce new ones
to replace old ones. This natural physiological process is controlled by our genetic
material. But if certain radiation disrupts this natural process, it will cause cancer.
Basically, cells keep on growing without reason. And this reason is radio nuclides.
! Another effect that can be caused is changes in DNA (changes to genetic material).
Two problems can happen because of this. One is Teratogenic changes and another is
genetic changes (mutations). What are teratogenic effects: birth defects. Mother is
exposed for long term to lower level of radiation (most sensitive in 8- 15 week of
pregnancy) ; her unborn child will have some problems like smaller head or brain size,
poorly formed eyes, mental retardation. Genetic mutations are changes that can be
transferred from the parent to the child. Teratogenic changes cannot be transferred to the
child, but the offspring is affected anyways, which we see when child is born.
2) Non-Stochastic effect These are acute effects. These effects are seen in humans that
are exposed to very high levels of radiation for a short period of time. These effects are
also very visible and obvious. These effects, if level of radiation increases, will get more
severe. We know this based on cases of many different nuclear accidents everywhere
(Chernobyl, Hiroshima Nagasaki, workers that are exposed to very high level of radiation
!Some literature says that these effects can cause cancer, but some literature disagrees
that it causes cancer. Based on Epidemiological studies and other examples, it seems that
yes these effects can cause cancer, because most data shows increased number of
different types of cancer in areas such as Chernobyl or where we saw some accidents.
! What we know for sure is that this high level of radiation causes radiation sickness
(nausea, weakness, hair loss, skin burn or diminishing organ function, premature aging,
death). Death comes usually after two to three months.
Nuclear power plant accidents
1) Three Mile Island, Pennsylvania, 1979: Researchers did not find much adverse effects
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