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RE: Radiation lesson - but the facts this time

<From: Wright Huntley <jwwiii at pacbell_net>
Subject: Radiation lesson.

Electromagnetic radiation comes in lots of useful forms.>

True

<The kind most used for sterilizing is usually called ionizing radiation.>

Also true.

<That can be anything from visible light and UV through soft to hard
x-rays.>

False. Visible light and UV are not ionizing radiation. If they were, we
would all be feeling woozy minutes after we were born, and not survive much
longer afterward.

<While capable of inducing serious chemical changes, and certainly of
destroying
living tissue (right dose and wavelengths), it does *not* leave any residual
radioactivity.>

Depends on what type of ionizing radiation you are looking at (see below).

<Much of ionizing radiation is poor at penetrating many solids, but all
materials seem to have windows that allow some radiation through (just like
glass passes sunlight). Lead, gold, and other heavy metals tend to be the
most
opaque at all wavelengths.>

For the most part true.

<Particle bombardment with neutrons and electrons (alpha and beta "rays")
may
penetrate some materials and can cause residual radioactivity if they
actually
split atoms into unstable isotopes. The kind used for killing salmonella in
ground beef is most unlikely to ever do that. It takes a pretty big
accelerator.>

Wrong. Alpha particles (there is no such thing as an alpha 'ray') consist of
2 protons and 2 neutrons (that is to say, a helium nucleus) that has been
ejected from the nucleus of very heavy radioactive elements, such as
uranium, radium, thorium. No such thing as a beta 'ray' either. Purely
particulate in the form of a high speed electron. Alpha and beta particles
do not penetrate materials because 1) for betas, of their electrical charge
2) for alphas, there huge size in comparison to the atomic world (like
trying to throw a baseball thru a chainlink fence).

Neutrons will penetrate, and usually pass through most matter. However, when
the collide with the nucleus of other atoms in the material, they increase
the atomic weight, usually making the matter radioactive. It is usually an
excess of neutrons in a nucleus that makes something radioactive. To my
knowledge, NONE of these is used to kill salmonella, or anything else, in
beef or anywhere else.

<None of them can be used on packages of widely different thickness and
contents to reliably kill microorganisms, so quit worrying about shipping
stuff in boxes. OK? They ain't gonna do it any time soon. Letters, maybe.
Boxes, no.>

True, that is why they don't even try. However, irradiation with gamma
'rays' (yes, there are gamma 'rays') is usually used in these here United
States to kill bacteria in sealed food packages, bacterial cultures in labs,
and many other uses. It is the energy of 'ray' type radiation
(electromagnetic radiation) that counts. While Visible light, UV,
microwaves, radiowaves are all electromagnetic energy, they are all
non-ionizing because they do not carry enough energy. X-rays are ionizing
but still do not have enough energy to kill bacteria in a reasonable
exposure time. However, gamma rays are ionizing and can be used for killing
bacteria if necessary. There is a gamma irradiator not far from here that
uses cobalt-60 gamma rays to irradiate food. These types of irradiators CAN
be used to kill anthrax or other bacteria in packages, letters, etc.

It is, however, unlikely that such a step would occur:
1) A huge source would be needed in order to expose large packages to the
levels of energy required to kill all of the bacteria inside.
2) There are not enough qualified individuals in the country tooversee these
types of operations. You are talking source quantities on the order of 1000
curies of activity. Compare that with levels usually seen in, say,
pharmaceutical labs where maybe 50 millicuries are used, and that would be a
very high number.

<The morons we elect to office, and the dimwit bureaucrats they like to hire
don't usually know very much physics.>

Can't argue with that.

<They do know they can get away with
extracting more money from you and hiring more underlings if they can scare
the pants off of you.>

If they can't find the source of these anthrax laced letters, which is
nearly impossible when these things are showing up all over the country with
different postmarks, I would rather they irradiate the mail than do nothing
at all. You can always ship fish/eggs via other methods (UPS, Fedex,
Airborne, etc.). You can always go to shows, auctions etc. to get more fish.
You can't, as several people have found out already, always get cured of
anthrax.

Joel Antkowiak
Health Physicist (so yes, radiation is my life)

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