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Q & A: Uses and dangers of radioactive elements

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Most recent answer: 04/09/2009
What are the positive and negative effects of radioactive elements?
- rachel (age 13)
roy.h mann , brooklyn
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)

Follow-Up #1: Possible dangers of alpha decay

What are the dangers of alpha decay
- Jonathan Ramoskiuygt (age 84)
Moscow, Russia
The dangers range from slight to large to lethal depending on the amount and location of the alpha radiation.   Alpha particles consist of doubly ionized helium atoms and arise from decay of radioactive nuclei.   Typically they have modest amounts of energy and cannot penetrate into matter very far, so clothing, a sheet of paper, or your own skin will stop them.  A more serious problem is if the radioactive source gets into the body, either into the lungs through inhalation of radioactive dust or ingestion by eating or drinking radioactive material.   Once inside the body they destroy cells due to heavy ionization and, again depending on the amount, can lead to sickness and even death..


(published on 11/27/2007)

Follow-Up #2: gamma radiation effects

what are the dangers of Gamma waves?
- dede (age 16)
Gamma radiation (extremely high-frequency electromagnetic radiation) can cause mutations in DNA and thus cause cancer.

Mike W.

(published on 09/14/2008)

Follow-Up #3: Analyzing radioactivity in soil

can one analyse the radioactive content in a soil and how
- wole alabi (age 30)
To measure the relative amount of radioactivity in soil is straightforward.  All you need is a simple Geiger counter.  However to determine the type of radioactivity is a bit more complicated.  A complete determination of the exact content requires some expensive equipment. 
You can get a crude idea of the type of radioactivity by investigating its penetrating power.
For example, alpha particles, which are helium nuclei, can be stopped by inserting a few sheets of paper between the source and the detector.  Beta rays, actually electrons, can penetrate paper but will be stopped by a thin sheet of aluminum.  Gamma rays, or high energy photons, can penetrate furthest and you need a thick piece of aluminum.  Lead is the best blocker of gamma rays.
See    for more information.


(published on 04/09/2009)

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