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Lecture 6

GGR203H1 Lecture Notes - Lecture 6: Indoor Air Quality, Electric Field, Interlocking

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Lecture 6
All around us
Cannot escape or control
It is a part of our planet
1. Background Radiation – it is natural radioactivity in the Earth and by
cosmic rays from outerspace. It can lead to mutation but does not
usually cause harm to humans
2. Manmade radiation – cause by electronic products and is harmful to the
human health
Some Sources:
X-rays machines
TV sets
These sources are controllable
Manmade Radiation is only 18% of all emitted radiations of which 4% is
emitted from nuclear medicines (used to cure cancer)
Natural Radiation is 82% of all emitted of which 55% is emitted by Radon.
Radiation can be divided into 2 groups based on the amount of energy
possessed by the radiation.
1. Ionized – High energy (cosmic, gamma rays, etc); it has short
wavelengths. However, there is enough energy to break down chemical
bonds and can harm our body.
2. Non Ionized – Low energy (TV, microwaves, etc); it has long
wavelengths. There is not enough energy to rearrange chemical
arrangement. The affects it has on human health is still debated by
How does ionized radiation cause health effects?
Radioactive material that decay spontaneously producing ionizing radiation
oStrip away electrons from atoms
oBreak some chemical bonds
Alpha, beta particles, gamma and x-rays (differ in the amount of energy they
Human Health effects from to radionuclides
Divided two categories
1. Stochastic Health Effects – Chronic
Long term, low level of exposure
Increased levels of exposure does not related to a high severity to
the adverse effects of radionuclides but increases the likelihood of
getting affected
I. Cancer: uncontrolled growth of cells. Radionuclides and
other carcinogens interfere with the genetic mechanism of
cell growth at the cell and molecular level
II. Changes in DNA: leads to mutation. It is teratogenic. This
means fetuses that are constantly exposed to radiation
suffer. It can lead to a small head size, mental retardation,
and disability.
2. Non-stochastic health effects – Acute
Short term, high level of exposure
Increased levels of exposure leads to more severe adverse effects
(e.g. nuclear power plant accidents)
Its effects are best studied of Japanese survivors of the Hiroshima
and Nagasaki bombings in WWII.
I. Cancerous Health Effects? Maybe and maybe not. Some
suggest children who are exposed may experience such
II. Radiation sickness: instant weakness, discoloration, skin
burn, hair loss, premature aging and can lead to death
Nuclear Power Plant Accident
Three Mile Island, PA (1979)
Chernobyl, U.S.S.R (1986) –had 10 to 20 times higher dose than the Three Mile
The effect of different doses of radiation on the human body after acute, whole body
oHighly Sensitive: breasts lungs, stomach, colon
oModerate Sensitive: brain, pancreas
oLow Sensitive: skin, bone, spleen, kidney, gall bladder
Is Any Amount of Radiation Safe
Some scientist believe low levels are beneficial and may cure some cancer but
can also cancer
How? Many cases prove this:
oFirst observed in 1910
oJapanese survivors of atomic bomb
oUranium miners
oMedical treatments
oChildren are more sensitive because they grow more rapidly
Chemical properties of Radionuclides
Determine where health effects occur in our body
Our organs cannot distinguish between the radioactive and non-radioactive
form of element
1. Radioactive Iodine in thyroid (body cannot tell it is radioactive and
absorb it regardless)
2. Calcium, Strontium-90 and Radium-226 accumulate in the bones
This is not good for our body
Yielded in breakdown of Uranium in soil, rock, and water (more often in ground
water). This leads to indoor air pollution. It enters the home through holes in
the home and circulates indoor air.
Causes lung cancer
It is odourless and colourless and therefore it cannot be detected
It is the 2nd leading cause of lung cancer in the US today
Non-Ionized Radiation
Microwave Radiation
oMany uses (mainly microwave)
Microwave Oven Radiation
Form of electromagnetic radiation
oUsed in cooking (easily absorbed by foods)
oPass through, glass, paper, plastic
oReferred by metal
Food is not harmed
However, food is not cooked evenly—that’s why microwave spins to help
distribute waves for even cooking
Microwaves bounce back and forth within the metal interior until they are
absorbed by the food
oWater molecule in food vibrate, producing heat that cooks the food
oFood is not radioactive/contaminated
oCooks from the outside and heat is conducted inside
Most microwaves nowadays are energy efficient
Microwave Oven Safety Standards
Implemented in 1971
Leaking cannot be more than: 5 mill watts per centimeter square at
approximately 2 inches from the oven surface
There are strict rules regarding these standards
There is a two interlocking system to prevent microwaves from escaping if door
accidently opens
Microwave Radiation and Human Health
How low affects affect human health is not known
oAnimal research genetics changes, immune responses
oHeats human tissue
oHarms eyes because eyes are sensitive to intense heat
oMicrowaves can cause cataracts
Painful burn
Temporary sterility
Smoke Detectors and Alarms
Ionization chambers: small amount of radioactive material encapsulated in a
metal chamber
oIt emits a low but steady current
When something is burning, the smoke or CO triggers the detector’s alarm
It releases a very small radiation until the source stays in detector apparatus
When the lifeline of this material is there is a proper procedure to dispose of
the capsule