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Why are radioactive substances harmful?

  1. Mar 29, 2005 #1
    What properties do radioactive substances have that actually cause harm to organisms? I've really no idea at all...

    Thanks alot,
    Jacob
     
  2. jcsd
  3. Mar 29, 2005 #2

    chroot

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    They cause ionization, kicking electrons out of atoms. The end result is that this ionization causes unwanted chemical reactions in the cell. The worst kind are those that damage DNA, prompting an increase in cancer risk.

    - Warren
     
  4. Mar 29, 2005 #3

    dextercioby

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    Let's see.Basically they cause cancer.They are particles (alpha particles,electrons or photons) with great energy and these energy is trasferred (by collisions or scatterings) to the nuclei & electrons of the atoms which compose the ADN of cells,perturbing their behavior,practically making them (the cells) multiply without any "logic" and therfore generating cancerigen tissues...

    This is the simplistic picture.Maybe someone will provide much more.

    Daniel.

    EDIT:Voilà,Warren beat me up it & he was more precise.
     
  5. Mar 29, 2005 #4
    So by touching a radioactive substance, the atoms that make up my body essentially would ionize and scatter electrons all into my body? What causes that to happen?
     
  6. Mar 29, 2005 #5

    dextercioby

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    Energy & momentum transfer.The point is not in "touching",but even being in the vecinity of radioactive elements (without a proper clothing) is dangerous.Touching or not the Pt/U/Po/As/Ra (...) is less relevant.The particles they emit are harmful...

    Daniel.
     
  7. Mar 29, 2005 #6

    chroot

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    Not even touching it; just being near enough to it that some of its radiation is striking you.

    Chemical reactions are universally driven by charge; the electromagnetic force is what makes chemistry happen. Chemistry is basically the study of electron configuration. Human beings, of course, are just elaborate and delicate chemical systems.

    Ionizing radiation starts knocking electrons out of molecules, causing them to break up in some cases, or stick together improperly in others. It can break the bonds between the bases of the double-helix of the DNA. It can cause proteins to fold improperly. In small doses, the cell has enough mechanisms to repair itself; there are enzymes that fix breaks in the DNA, for example. The cell can break apart misfolded proteins, or eject unwanted chemicals from the cell entirely.

    When exposed to a large amount of radiation, the cell's defenses are overwhelmed. The DNA can be so badly damaged that the enzymes (which are brainless automatons, not really "knowing" what they're doing) can put the DNA back together improperly. The cell can be overwhelmed with a buildup of unwanted broken goop, much of which is still reactive and interferes with the rest of the cell's activities. Eventually, the cell commits suicide.

    - Warren
     
  8. Mar 29, 2005 #7
    So they don't cause my atoms to ionize, they themselves are constantly ionizing and shooting off electrons?
     
  9. Mar 29, 2005 #8

    chroot

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    There are several kinds of radiation: alpha, beta, and gamma.

    Alpha radiation is composed of helium nuclei; these are not very penetrating, cannot pass skin, and generally cause no harm unless the substances are inhaled or ingested.

    Beta radiation are energetic electrons. These can penetrate a short distance through skin, so are dangerous even at a distance. The electrons collide with atoms in your body and knock other electrons from the atoms to which they "belong."

    The third kind of radiation, gamma, is composed of high energy photons -- like more aggressive X-rays. These photons can penetrate your entire body, and can knock electrons off anywhere.

    The radioactive substances undergo nuclear reactions which produce the alpha, beta, or gamma radiation; this radiation then ionizes atoms in your body, causing cellular damage.

    - Warren
     
  10. Mar 29, 2005 #9

    Astronuc

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    Alpha particles, usually up to about 5 MeV, generally are stopped by the skin. They are only harmful, as chroot mentioned, if inhaled - damage to lung - and ingested. Some alpha emitters, e.g. Pu, will find their way to bones - leukemia risk.

    Beta particles are more penetrating (cm's) and gamma rays are even more penetrating.

    The radiation can break chemical bonds, thus destroying DNA (mutations or complete destruction), enzymes (biological processes), and basically other structures in the cell, thus causing cell mortality.

    In addition, radiolysis of H2O produces H2O2, which is a powerful oxidizer. Peroxides interact with the other macromolecules destroying them, thus interfering with cellular process, which can cause cell mortality.

    The death of a few cells can be tolerated, but the death of many can lead to necrosis.

    Severe radiation exposure can damage or destroy the central nervous system, and at such levels, the result is a very painful death.
     
  11. Mar 29, 2005 #10

    Janitor

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    I once read an article about the medical fate of women who had the job of applying radioactive paint to watch dials. They licked the paintbrush to bring the bristles to a point. After doing this for some time, they developed necrosis of the jaw, and possibly cancer as well.
     
  12. Mar 29, 2005 #11
    What causes radioactive substances to shoot off alpha and gamma particles? I assume beta particles are caused by a highly unstable valence shell which is just "getting rid of" a few excess electrons to get a more stable electron configuration. Is that correct?

    Also, do different radioactive substances give off different kinds of radiation based on their identity, or is it like they all initially give off gamma rays until they run out of energy for that, then give off beta particles, then alpha particles?
     
    Last edited: Mar 29, 2005
  13. Mar 29, 2005 #12

    Astronuc

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    Radioactive decay arises from the fact that the nucleus has excess energy, and the way to get rid of it is to emit radiation.

    The beta particles comes from a neutron - http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/beta.html#c2

    Positrons occur when a nucleus has an excess of protons or is neutron deficient. In positron emission, a proton transforms into a neutron.

    Alpha particles occur in the heavier elements and are an efficient way to dump a lot of energy - MeV range.

    Gamma radiation occurs in conjunction with either alpha or beta decay, where the daughter nucleus dumps the remaining energy after the primary decay.

    The radioactive paint on watch/clock dials contained radium, which behaves chemically like calcium. The radium was aborbed and deposited into the jaw bones and others as well. The alpha particles, and gammas, irradiated from inside the bone and tissue.

    These may also help - http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radact.html#c2

    http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radser.html#c1
     
    Last edited: Mar 29, 2005
  14. Apr 5, 2005 #13

    vanesch

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    Let's also add a few others:
    *) a most nasty form of radiation is fast neutrons: they are very damaging because they mainly interact with nucleae and have high penetrating power ; so they do not ionise so much, as that they knock away nucleae out of the molecule. Talk about irreversible damage :-)

    *) cosmic radiation. At ground level, they mostly consist of energetic muons (which are a bit like heavy electrons) and fast neutrons. In outer space, or high altitudes, charged hadrons (fast protons, pions...) are also present: these are very damaging dudes, because they both ionise and knock off nucleae. But they rarely get down to sea level because they interact in the atmosphere (producing pions which then decay into muons, and neutrons).

    *) piramid radiation: extremely damaging: it causes irremediable damage to the mind ;-)

    cheers,
    Patrick.
     
  15. Apr 15, 2005 #14
    Pardon me for asking, but why arn't these 3 'additional' radiation not on the usual list of harmful radiation?
     
  16. Apr 21, 2005 #15
    So, since beta radiation is just electrons, what is the difference between them and a bolt of lightning? Could I get cancer from a bolt of lightning?
     
  17. Apr 21, 2005 #16
    I think if you get hit by a bolt of lightning, you're going to have more pressing things to worry about besides an increase in the long-term risk of cancer due to the high electron flux in a lightning bolt.
     
  18. Apr 22, 2005 #17

    Claude Bile

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    Electricity is a net drift of electrons, the electrons formed from Beta decay have a very high energy. Similar to how Gamma rays are much more harmful than infrared rays even though they are really the same elementary particle. The key difference is the energy of the particle.

    Claude.
     
  19. Apr 23, 2005 #18
    Alpha particles exceed 8 Mev in some cases - Alphas are usually accompanied low energy Gammas, e.g., U238 4.5 MeV alphas also make 48 KeV gammas.
    Betas are also accompanied by gammas that are sometimes more energetic than 3MeV.
    Vanesh is right in mentioning neutrons; they go right through many metals except Li, Be, Boron and especially hydrogen atoms which they knock off creating anions and lots of acidic protons. Neutrons normally pass through the whole human body and burn the far-side about as badly as the front-side. My colleague, Harry who received a 50/50 fatal probability dose of ~600R died in about 30 days but the inside of his mouth was charred black and the metal in his teeth had to be removed lest its induced radiation burned his tissue further.
    When yellow smoke (incendiary UO3) is breathed a microgram particle not only emits about 40 alphas per hour but the same number of 48 KeV gammas and contributes a lot of heavy metal poisoning damage and radioactive damage from that which gets retained by the body.
    Another unmentioned source of radiation damage are fission fragments the distributtion of which peaks at two masses, one at perhps atomic weight of 92 u and the other near 133 u; that is why Strontium-90 and Iodine-~132 are the renowned bad ones as far as anmals are concerned. Cheers, Jim
     
  20. Apr 24, 2005 #19

    Astronuc

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    Here's some info on lightning - http://hyperphysics.phy-astr.gsu.edu/hbase/electric/lightning2.html

    The site states electrical potentials in the millions of volts, but I believe that is too high. However, the electrons are not accelerated into the MeV range, due to the breakdown of the air molecules.

    Typical lightning currents are on the order of 10's of kiloamps, although currents up to 200 kA have been reported.

    Lightning will not cause cancer, but if it close enough, it can kill or cause severe injury (burns, or neurological damage). The lighning temperature is on the order of 10,000 - 30,000 K and will produce ultraviolet light in addition to photons in the optical range. Ozone is also produced.
     
  21. Apr 26, 2005 #20
    It is the sum of the potentials along the lightning path that reaches the millions of volts (~ the energy of E field required to ionize/tranfert the electrons of all the atoms along the path of the lightning). Indivually, the electrons are accelerated moderatly (charge transfert).

    Seratend.
     
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