Understanding Radiation

capricioustelephoneΠολεοδομικά Έργα

16 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

68 εμφανίσεις

Understanding
Radiation


Luiza

Gharibyan

Yerevan State Medical University

Ionizing radiation includes
electromagnetic radiation
with enough energy to break
chemical bonds through
nonthermal process (X and
gamma photons or “rays”);
and high
-
speed subatomic
particles.



Ionizing radiation can be
produced by electrical devices
such as X
-
ray machines.



Ionizing radiation also can
arise from nuclear processes
such as radioactivity (alpha, beta,
and gamma emissions commonly
are associated with radioactivity),
nuclear fission and fusion and
from outer space.







Nonionizing radiation is
electromagnetic radiation with
insufficient energy to break
chemical bonds through
nonthermal processes.


Examples of nonionizing radiation
include radio and TV transmissions;
microwaves and radar; and infared,
visible and ultraviolet lihjt (including
that produced by lasers).






Nonionizing radiation is also
known as electromagnetic field.
The ancients knew of lodestones,
static electricity and lightning.


They knew that lightning, the
thunderbolt of the gods, could kill
or injure. But it was not until the
19 century that scientists began
to understand electric and
magnetic fields and their extend
in space.







X
-
rays were discovered in 1895
by Rontgen, radioactivity and its
associated radiations in 1896 by
Becquerel.


Soon afterward the harmful
effects of ionizing radiation
became known and controversies
about its risk benefits began.









Radioactive atoms undergo
spontaneous nuclear

transformations and release
excess energy in the form of
ionizing radiation.


The body attempts to repair the
damage, but sometimes the damage
is too severe or widespread, or
mistakes are made in the natural
repair process.









The most common forms
of ionizing radiation are
alpha

and
beta

particles,
or
gamma

and X
-
rays.












What kinds of health effects
occur from exposure to
radionuclides?


In general, the amount and
duration of radiation exposure
affects the severity or type of
health effect.



There are two broad
categories of health effects:
stochastic and non
-
stochastic


Stochastic Health Effects



Stochastic effects are
associated with long
-
term,
low
-
level (chronic) exposure
to radiation. ("Stochastic"
refers to the likelihood that
something will happen.)

Increased levels of
exposure make these health
effects more likely to occur,
but do not influence the
type or severity of the
effect.


Cancer is considered by
most people the primary
health effect from
radiation exposure.

Radiation can cause changes
in DNA, the "blueprints" that
ensure cell repair and
replacement produces a
perfect copy of the original
cell. Changes in DNA are
called mutations.


Non
-
Stochastic
Health Effects


Is any amount of
radiation safe?


How do we know radiation
causes cancer?

Aren’t children more
sensitive to radiation than
adults?

Effects of Radiation Type
and Exposure Pathway.


Non
-
Radiation Health
Effects of Radionuclides.

Do chemical properties of
radionuclides contribute to
radiation health effects?


Radioactive
iodine
concentrates in the thyroid.

Calcium,
strontium
-
90
, and
radium
-
226

have similar
chemical properties.

Estimating
Health Effects


What is the cancer risk
from radiation?
How does it compare to the
risk of cancer from other
sources?


What are the risks of other
long
-
term health effects?

Other than cancer, the most
prominent long
-
term health
effects are teratogenic and
genetic mutations.



Genetic effects


Protecting Against Exposure

What limits does EPA set on
exposure to radiation?


How does EPA protect
against radionuclides that
are also toxic?