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Lecture 6

EESA10H3 Lecture Notes - Lecture 6: Ionizing Radiation, Microwave Oven, Tumor Suppressor Gene

Environmental Science
Course Code
Silvija Stefanovic

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University of Toronto Winter 2016
at Scarborough
Lecture 6: Radiation and Human Health
Intent of the course:
We can not escape from radiation
Types of Radiation:
(A) Sorted by where its comes from
1. Background radiation: Natural radioactivity in the Earth and by cosmic rays from outer space which can not be
2. Manmade radiation — which are included in some electronic products: X-ray machines, X ray diagnostic, Television
sets, Microwave ovens, Radar devices, Lasers. It’s hard to be controlled, but it can be controlled.
[others manmade radiation]
Nuclear Missiles: Nuclear bombs have been exploded by humans, releasing radiation into the environment.
Nuclear power: Nuclear power stations have released radiation into the environment
Q1: Look at the following pie chart and try to figure the data:
From the chart, we can find that most of the
radiation around us comes from nature
radiation ( the most portion of it is radon gas
form the ground ), and around 12.5% of them are
from artificial sources. The most portion of
artificial radiation comes from medical
Q2: How the radiation comes to the ground?
— Rain washing radioactive materials out of the air
— Internal dose from radioactive materials in the air
— Internal dose from eating and drinking radioactive materials in food
— Internal dose from creating in sea spray and sand
— External radiation direct from the cloud
— External dose direct from radioactive materials deposited on the ground C. Shen ©
Type of radiation
Cosmic rays
Radiation that reaches the Earth
from outer space
All animals emit natural levels of
Some rocks give off radioactive
radon gas
Soil and plants
Radioactive materials from rocks
in the ground are absorbed by the
soil and hence passed on to plants

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(B) Sorted by whether it can be ionized or not
1. Radiation is generally classified ionizing or non-ionizing, based on whether it has enough energy to knock electrons off
atoms that it interacts with, as well as being able to do lower-energy damage such as breaking chemical bonds in
2. Ionizing radiation (High energy, short wavelength): which is caused by unstable atoms giving off energy to reach a
more stable state, is more of a health threat to humans because it involves changing the basic makeup of atoms in cells, and
more specifically the DNA molecules inside of cells. It does, of course, take a very strong dose of radiation to
substantially damage a cell’s structure, as there can be trillions of atoms in a single cell. Alpha, beta particles, gamma
and x-rays (differ in the amount of energy they have)
3. Non-ionizing radiation (Low energy, long wavelength): such as radio and microwave energy, is considered harmful only
to the extent of the amount of heat energy it transfers to whatever it hits. This is, in fact, the way that microwaves cook
food. UV light is unique in that while it is non-ionizing, it does have the capacity to cause harmful effects similar to what
ionizing radiation can create, such as an increased risk of cancer due to damage to DNA molecules.
Ionizing radiation
Q3: How does Ionized Radiation Cause Health Effects?
1. Stochastic health effects — Chronic
Features: a. Long term, low level of exposure; b. Increase levels of exposure make these effects more likely to occur but
do not influence the type or severity of the effect
(A) Changes in DNA — mutations
a. Teratogenic (fetus most sensitive in 8-15 week of pregnancy, smaller head or brain size, poorly formed eyes, and mental
b. Genetic (passed from parent to child)
(B) Cancer — uncontrolled growth of cells
a. Damage at the cellular or molecular level
2. Non-stochastic health effects — Acute
Features: a. Short term, high level of exposure; b. Increase levels of exposure make these effects more severe
(A) Radiation sickness
a. Nausea, weakness, hair loss, skin burn or diminishing organ function, premature aging, and death
(B) Cancer — uncontrolled growth of cells
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