Radioactive elements have a lot of important uses and they also cause
some dangerous problems if they are not handled properly.
Henri Becquerel first found out about radioactive elements late in
the 19th century by placing some photograpic film under uranium salts.
The film was in a light-tight envelope, and it was exposed where he put
the uranium on it. This behavior was eventually found to be caused by
the emission of radiation from the decaying uranium which penetrated
the paper envelope and exposed the film.
Ever since then, more elements have been investigated for their
radioactivity, and different isotopes of elements have different
radioactive behavior. Many are used commercially and medically, and
others are just nuisances. I'll list some of the uses:
Small amounts of radioactive materials can be ingested as
"radiotracers" to see how certain chemicals are taken up by the body.
If a health researcher is interested in how a certain element is
distributed by the body after it is ingested, he can choose to use a
radioactive isotope of a common element, mix it in, and then use
sensitive radiaion detectors to see where it ends up in the body. These
are often used in studies to see how medications are absorbed and
transported within the body.
Thorium, a naturally ocurring radioactive element, is used in
making mantles for gas and kerosene lamps because thorium oxide glows
brightly when heated.
The radioactive elements uranium and plutonium are used in the generation of electricity in nuclear power plants.
Small radiactive sources of particles are used in many home smoke detectors.
These elements are also used in the production of nuclear weapons.
One can propose that the presence of nuclear weapons has prevented war,
but also that they have made the consequences of possible war much much
worse than before.
Depleted uranium, that is, naturally ocurring uranium with the U235
taken out, is mostly U238, which is a bit less radioactive than the
natural material. This material is very dense and hard, however, and
otherwise useless, so the army uses it to make bullets and other
shells. These can pierce steel armor. Whether this is a good use or a
bad use depends on which side of the gun you're standing on, I suppose.
Some radioactive elements glow because of their radioactive decays.
They emit electrons or alpha particles, changing from one kind of
element to another, and as the electrons in the atoms rearrange
themselves to the new atom's configuration, they emit light. Radium was
used for watch dials because it glows green. Tritium can also be used
as a backlight in watches because it too glows green. Tritium is still
used in small quantities in small vials on watch hands and to mark the
hour positions on watch dials. Radium isn't used anymore, however.
Now for some negative effects:
Radiation, even in small doses, can cause cancer in humans and
other living things. Fast moving photons (gamma rays), electrons (beta
rays) and helium nuclei (alpha particles) can crash into other
molecules and change their structure. If this happens to a DNA
molecule, it can damage the genetic information, and sometimes turn a
cell cancerous. Radiation also causes burns, much like sunburn, in
large doses over short amounts of time.
Usually you can walk away from radioactive substances, lowering
your risk. But if you ingest radioactive elements, they stay with you.
Particulrly nasty radioactive elements include radon and radioactive
iodine. Radon is a chemically inert gas with a short half-life (and
therefore decays rapidly, emitting radiation faster than other
elements). It is produced naturally as a decay product of longer-lived
radioactive elements in rock and soil. It may diffuse through basement
walls and into people's homes. It increases the rate of lung cancer
when people breathe it in. It is a good idea to ventilate basements and
have them checked, particularly in areas of the country where radon is
common.
Radioactive iodine is also readily absorbed by the body and becomes
incorporated in bones, and is therefore difficult to eliminate from the
body. The radiation it emits can cause bone cancer over long periods of
time.
The radium on watch dials was incorporated in paint. Workers used
to paint the watch dials by hand, and some would even lick their paint
brushes to make a sharper tip. They ingested radon paint, and some
became ill with cancer.
Naturally ocurring uranium also was used to make bright yellow paint, but I believe this too has been stopped.
Some people complain about radiation emitted by those
depleted-uranium bullets and shells left over in wars. Residents of
areas where such munitions have been used are concerned about the
long-term health effects of the radioactivity. There is some concern
that the main dangers from the leftover uranium dust may be due to
chemical poisoning rather than radiation.
Plutonium, while radioactive, also happens to be just plain
poisonous. Human bodies do not deal well with heavy metals: lead,
mercury, and arsenic come to mind as things not to ingest because they
are poisonous. Plutonium may well be the most poisonous of the lot.
Tom (w mike)
(published on 10/22/2007)
