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Re: Ionizing radiation vs microwaves



Hi Dale and  Greg,
Ultraviolet radiation (UV) is not ionizing radiation! UV damages DNA
causing toxicity to cells by  producing pyrimidine (  notably thymine)
dimers that cross link DNA strands  or distort single strands  causing
distortion and errors in replication.
Ionizing radiation consists, mainly ,of beta electrons or gamma rays,
x-rays  are similar to  gamma rays  and finally apha particles that are
very short ranged but energetic. Food irradiation is mainly done using
gamma irradiation form isotope sources but x-rays can be used. Gamma and
X-rays damage DNA by causing strand breaks and adducts. DNA adducts are
modified forms of guanine mainly  and these persist and damage if
consumed.  Ionizing radiation also produces  adducts from protein and
lipid. The lipid based adducts are those most concerning regulators but
all of the adducts are persistent and nasty.
I am enclosing below the EPA basics on ionizing
radiation:http://www.epa.gov/radiation/docs/ionize/ionize.htmIonizing
Radiation Fact Sheet Series:
No. 1


Ionizing radiation is radiation that has sufficient energy to remove
electrons from atoms. In this document, it will be referred to simply as
radiation. One source of radiation is the nuclei of unstable atoms. For
these radioactive atoms (also referred to as radionuclides or
radioisotopes) to become more stable, the nuclei eject or emit subatomic
particles and high-energy photons (gamma rays). This process is called
radioactive decay. Unstable isotopes of radium, radon, uranium, and
thorium, for example, exist naturally. Others are continually being made
naturally or by human activities such as the splitting of atoms in a
nuclear reactor. Either way, they release ionizing radiation. The major
types of radiation emitted as a result of spontaneous decay are alpha
and beta particles, and gamma rays. X rays, another major type of
radiation, arise from processes outside of the nucleus.
Alpha Particles

   Alpha particles are energetic, positively charged particles (helium
nuclei) that rapidly lose energy when passing through matter. They are
commonly emitted in the radioactive decay of the heaviest radioactive
elements such as uranium and radium as well as by some manmade elements.
Alpha particles lose energy rapidly in matter and do not penetrate very
far; however, they can cause damage over their short path through
tissue. These particles are usually completely absorbed by the outer
dead layer of the human skin and, so, alpha emitting radioisotopes are
not a hazard outside the body. However, they can be very harmful if they
are ingested or inhaled. Alpha particles can be stopped completely by a
sheet of paper.
In conclusion, nobody , outside of , perhaps, one considers UV to be
ionizing radiation, it just aint!
Sincerely, Joe

Beta Particles

   Beta particles are fast moving, positively or negatively charged
electrons emitted from the nucleus during radioactive decay. Humans are
exposed to beta particles from manmade and natural sources such as
tritium, carbon-14, and strontium-90. Beta particles are more
penetrating than alpha particles, but are less damaging over equally
traveled distances. Some beta particles are capable of penetrating the
skin and causing radiation damage; however, as with alpha emitters, beta
emitters are generally more hazardous when they are inhaled or ingested.
Beta particles travel appreciable distances in air, but can be reduced
or stopped by a layer of clothing or by a few millimeters of a substance
such as aluminum.

Gamma Rays

   Like visible light and x rays, gamma rays are weightless packets of
energy called photons. Gamma rays often accompany the emission of alpha
or beta particles from a nucleus. They have neither a charge nor a mass
and are very penetrating. One source of gamma rays in the environment is
naturally occurring potassium-40. Manmade sources include plutonium-239
and cesium-137. Gamma rays can easily pass completely through the human
body or be absorbed by tissue, thus constituting a radiation hazard for
the entire body. Several feet of concrete or a few inches of lead may be
required to stop the more energetic gamma rays.

X Rays

   X rays are high-energy photons produced by the interaction of
charged particles with matter. X rays and gamma rays have essentially
the same properties, but differ in origin; i.e., x rays are emitted from
processes outside the nucleus, while gamma rays originate inside the
nucleus. They are generally lower in energy and therefore less
penetrating than gamma rays. Literally thousands of x-ray machines are
used daily in medicine and industry for examinations, inspections, and
process controls. X rays are also used for cancer therapy to destroy
malignant cells. Because of their many uses, x rays are the single
largest source of manmade radiation exposure. A few millimeters of lead
can stop medical x rays.



Dale Wilson wrote:

Greg,



I am of 2 minds when it comes to food irradiation, after all, when
you get right down to it, that is what happens when anyone uses a
microwave to cook something.  After all, there is a reason why they
call it "nuking the food". I personally don't see any difference
between the two, not without more testing anyway.



Microwaves are NOT ionizing radiation, but UV, electron beams, and
X-rays are.  What this means is that the energy of the photons (or
electrons) is great enough to split water molecules.  The hydroxyl
radicals thus formed, kill bacteria by nicking DNA and ripping up
membranes and proteins.  That is why you get a suntan (and maybe skin
cancer) from short-wave UV.

The hydroxyl radicals dissipate in a few microseconds after the
radiation ceases, but some people are concerned that byproducts of
these reactions in food could be harmful.

Dale

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