Radioactivity is invisible. We are also unable to hear, taste, touch, or smell it. Yet we
are able to detect and measure radioactivity with certain scientific instruments such
as a Geiger counter. This device allows us to use radioactivity safely because it lets us
know when even tiny amounts of radiation are present.
The rock layers exposed in
the Grand Canyon
represent intervals of
time stretching back
hundreds of millions of years.
Radioactivity is a scientific process. One of the most important ideas in all of Earth science is the concept
of geologic time. Because Earth is covered in rocks, radioactivity can be used to determine the age of the
Earth. Radioactive decay of unstable isotopes contained in rock layers can be used to determine the
absolute age of the rocks. Radioactive decay occurs when the original parent isotope is converted to a
daughter atom. Radioactive decay is measured in half-lives, which is the length of time taken for one-half
of the radioactive material to decay. The half-life of an isotope is the time taken for half of the original
parent isotopes to decrease to daughter atoms.
Are they the same thing?
Radioactivity is the name given to the processes where an
unstable nucleus of an atom changes into a different nucleus.
Particles such as alpha, beta and gamma are given off during
the change. The disintegration process of these particles is
known as nuclear radiation.
Radiation is technically any form of energy that can travel
through space in the form of waves. So, light, microwaves
and radio/TV broadcasting waves are all technically forms of
radiation, but are not produced by radioactivity.
What do the following
materials have to do with
each other?
•Rock samples
•Fiestaware
pottery dishes
•Bananas
•Coleman
lantern mantle
•TV set
•Phosphate
fertilizer
•Brick
DETECTION OF RADIOACTIVITY
Yes. Most radioactive substances enter our bodies as part of food, water or air. Our bodies use the radioactive as well as the nonradioa
Yes. Most radioactive substances enter our bodies
as part of food, water or air. Our bodies use
radioactive as well as the nonradioactive forms of
vital nutrients, such as iodine and sodium.
Radioactivity can be found at every step of the
food chain. It is even in our drinking water.
Yes. Another type of natural radiation is cosmic radiation from the
Sun and outer space. Because Earth’s atmosphere absorbs some of
this radiation, locations at higher altitudes receive more exposure. In
Ohio, for example, the average resident receives a dose of about 40
millirem in one year from cosmic radiation. In Colorado, it is about
180 millirem in one year. Generally, for each 100-foot increase in
altitude, there is an increased dose of one millirem per year.
Flying in an airplane increases our exposure to cosmic radiation. A
coast-to-coast round trip gives us a dose of about four millirem.
Yes. Radiation in soil and rocks contributes about 60
millirem in one year to our exposure. In Colorado, it is
about 105 millirem per year. In India, radioactivity from soil
and rocks can be 3,000 millirem per year, and at a beach in
Brazil, it is over 5 millirem in a single hour -- but only a few
residents who use that beach receive doses in excess of
500 millirem per year.
Yes. If you live in a wood house, the natural radioactivity
in the building materials gives you a dose of 30 to 50
millirem per year. In a brick house, it is 50 to 100 millirem
per year. And, if your home is so tightly sealed that there
is little ventilation, natural radioactive gases (radon) can
be trapped for a longer period of time and thus increase
your dose. Even some granite countertops (particularly
reds and purples) may contain some radioactivity.
Yes, it’s true we can’t escape from radioactivity in our everyday
environment. Each person with whom we spend eight hours a day
gives us a dose of about 0.1 millirem in a year.
Using a gas stove increases the dose by about 2 millirem per year
because of radioactive materials in the natural gas.
A person who smokes two packs of cigarettes a day receives a
radiation dose of about 1,300 millrem per year. This is because
polonium (a radioactive element) is part of the smoke and when
inhaled, it gets trapped in the lungs.
RADIATION REALLY IS EVERYWHERE.
Every day we are exposed to a constant stream of radiation from
the Sun and outer space. Radioactivity is in the ground, air, the
buildings we live in, the food we eat, the water we drink, and the
products we use. Remember that lead barrier apron you wear when
you get x-rays done at the dentist’s office? The average person in
the United States receives a dose of about 360 millirem per year
from natural sources of radioactivity as well as from typical medical
radiation exposures.
Is it true that we can’t live without
radioactivity?
Yes, it’s true. Our bodies are radioactive. It’s a simple fact of nature. But
there is no cause for alarm. These very small but detectable levels of
radioactivity are natural . . . as natural as life itself.
To put this into perspective… although one’s risk increases with
increased exposure, no harmful effects have ever been observed at
levels below 5,000 millirem. In fact, effects seen when humans are
exposed to 100,000 millirem over a short time period are temporary
and can be reversible. It takes a short-term dose of more than 500,000
millirem to cause a fatality so the level of radiation you receive and the
rate you receive it in is important.
What happened in Japan?
People in Japan that lived within 12 miles of the March 2011
Fukushima earthquake/nuclear meltdown disaster area were
exposed to …
What happened in Japan?
What happened in Japan?
What happened in Japan?
In March 2011, Japanese officials announced that
"radioactive iodine-131 exceeding safety limits for infants had
been detected at 18 water-purification plants in Tokyo and
five other prefectures". As of July 2011, the Japanese
government was still unable to control the spread of
radioactive material into the nation’s food. Radioactive
material was detected in a range of produce, including
spinach, tea leaves, milk, fish and beef, up to 200 miles from
the nuclear plant. Inside the 12-mile evacuation zone around
the plant, all farming has been abandoned.
Nuclear radiation leak in Japan
Half-life of…
Radioactive iodine-131
8.0197 days
The fate of Japan…
As of February 2012, the crippled Fukushima nuclear plant
is still leaking radiation and areas surrounding it could
remain uninhabitable for decades due to high radiation. It
could take “more than 20 years before residents could
safely return to areas with current radiation readings of
200 mSv/h (millisieverts) per year, and a decade for areas
at 100 mSv/h per year”.
So how much is a millirem?
A rem is a large dose of radiation, so the millirem (mrem), which is one
thousandth (1/1000th) of a rem, is used for the dosages of radiation
received from medical x-rays or for other medical diagnostic purposes.
An acute whole-body dose of under 50 rem will produce nothing other
than blood changes. 50 to 200 rem may cause illness but will rarely be
fatal. Doses of 200 to 1,000 rem will probably cause serious. Doses of
more than 1,000 rems are almost invariably fatal.
1 Sv = 100 rem
0.000010 Sv = 0.010 mSv
So, should we be concerned that there
is radioactivity in our everyday
environment?
No, not unless you get exposed to too much over a short period of time.