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Lecture

Week 7 Lecture


Department
Environmental Science
Course Code
EESA10H3
Professor
Jovan Stefanovic

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Radiation and Human Health
Radiation and Human Health
We cannot escape radiation
1. Background radiation - Natural radioactivity in the Earth and by cosmic rays from
outer space
Cannot be controlled
No serious human health impact
2. Manmade radiation - electronic products:
X-ray machines
X ray diagnostic
Television sets
Microwave ovens
Radar devices
Lasers
Can be controlled
Serious human health impacts
Ionizing Radiation Exposure to the Public
55% of the total radiation comes from radon
Natural radiation 82%
Man-made radiation is 18%
Radiation and Human Health
Ionised radiation
oHave high energy, able to release photon which can push out electrons
from the chemical compounds from our body and ionize them
oThey can also break down the chemicals in our body, they have
enough energy to do that
oThey are short waves
oWe know there are harmful human impacts
Non-ionized radiation
oThey have low energy, cannot remove the electrons, cannot break the
compounds in our body, and have long waves
Ionised radiation
How does ionised radiation cause health effects?
Radioactive material that decay spontaneously produce ionizing radiation
o Strip away electrons from atoms (create two charged ions)
o Break some chemical bonds
Alpha, beta particles, gamma and xrays (differ in the amount of energy they
have)
Health effects from exposure to radionuclides
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1. Stochastic health effects - Chronic
Long term, low level of exposure
Increase levels of exposure make these effects more likely to occur but do not
influence the type or severity of the effect
i.Cancer- uncontrolled growth of cells
oDamage at the cellular or molecular level
oRadiation interacts with normal mechanism that controls cells, so that
our tissue will start multiplying uncontrollably and creating cancer
ii.Changes in DNA- mutations
oTeratogenic (fetus most sensitive in 8-15 week of pregnancy, smaller
head or brain size, poorly formed eyes, mental retardation)
Fetus has been exposed to radiation directly, will not be
transferred to another generation
oGenetic (passed from parent to child)
E.g.
2. Non-stochastic health effects - Acute
Short term, high level of exposure
Increase levels of exposure make these effects more severe
i.Cancerous health effects, Yes or No
ii.Radiation sickness (nausea, weakness, hair loss, skin burn or diminishing
organ function, premature aging, death)
Nuclear power plant accidents
Three Mile Island, Pennsylvania, 1979
Chernobyl, former Soviet Union, 1986
Chernobyl accident had 10-20 times higher dose of exposure than Three
Mile Islands accident
The effect of different doses of radiation on the human body after acute, whole-
body exposure
Lungs, breast (breast cancer increased)
Is any amount of radiation safe?
Some scientist think that low levels of radiation are beneficial
How do we know radiation causes cancer?
o In 1910 observed that radiation cause skin cancer
o Japanese atomic bomb blast survivors
o Uranium miners have been exposed to high radiation for centuries
o Medical treatments
o Children more sensitive because they are growing more rapidly
Chemical properties of radionuclides
Chemical properties determine where health effects occur
Organs cannot distinguish between radioactive and non-radioactive forms
of element
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