EVS 1501 Lecture Notes - Lecture 11: Teratology, Radiography, Nuclear Medicine

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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
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.
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
Ionized Radiation
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
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