>From University Science News
Radiation That Kills Anthrax Won't Hurt Other
Mail
Sterilizing the mail with radiation to kill deadly
anthrax won't
damage most things being mailed, said Dr. Les Braby,
a
nuclear engineer at Texas A&M University.
With the recent spread of anthrax through the mail,
the United
States Postal Service (USPS) announced it would
begin using
radiation to kill the deadly bacteria. But some
researchers
wondered what would happen to the items being
sterilized.
"People send all kinds of things in the mail --
photographs,
computer disks, CDs," Braby said. "Gardeners send
seeds
through the mail. Doctors send biological samples
for analysis
through the mail. Irradiation won't make the mail
radioactive,
but beyond that, we need to know what happens to
this stuff
when it's irradiated."
Electron-beam, or e-beam, radiation is the same
process
used to irradiate food and medical equipment to kill
harmful
germs. Beams of electrons are fired at ultra-high
speeds to
break up the bacteria's DNA, killing the germs.
Researchers worried that the high doses of radiation
needed
to kill anthrax spores could damage items being
mailed, Braby
said.
****** "Seeds are pretty much destroyed and
unprocessed film
overexposed by the radiation," *********
Braby said. "But CDs and
computer disks survive the radiation process without
damage.
It's hard to visualize a physical process where
electron-beam
radiation would wipe out information stored in
magnetic form,
as in floppy disks and videotapes."
To test these theories, Braby and his colleagues at
the
Nuclear Science Center at the Texas Engineering
Experiment
Station used radiation on photographs and computer
disks.
"We started with a dose of 5.5 kiloGrays, which is
at the low
end of what we would expect to be used for
sanitizing mail,"
Braby says. "The radiation produced no errors in a
3½-inch
floppy computer disk. I expected the photos to be
bleached
by the radiation, like they'd been left in the sun
for a while, but
the radiation did not produce a noticeable change in
the color
balance of the prints."
In the next run, Braby increased the radiation dose
to almost
four times the initial dose and include some
writeable CDs in
the test. At 20 kiloGrays of radiation, photos,
computer disks
and CDs again showed no signs of damage.
"Twenty kiloGrays is a large enough dose to kill the
anthrax
spores in the mail," Braby said. "That is probably
the highest
dose the postal service would use and there was no
damage
to the items we tested." - By Mark Evans
[Contact: Mark Evans]
14-Nov-2001
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