Electron beams zap postal Anthrax

Electron beam sterilization zaps anthrax for mail

By Louise Elliot, Regional Editor -- Design News, January 9, 2002

San Diego, CA - When several people died and hundreds of others were infected after handling mail sabotaged with Anthrax spores, the Post Office started to send mail to a Lima, OH electron beam sterilization facility that usually contracts to kill E.Coli and salmonella bacteria in ground beef. The process worked so well and so quickly for the Anthrax-exposed mail that the Post Office gave Titan Corp.'s SureBeam subsidiary a $26 million contract to provide eight turnkey electron beam systems-with the option to buy another 12.

Electron beam irradiation uses electricity channeled by a linear accelerator to accelerate electrons at the speed of light. When the electron beams hit the Anthrax bacteria, they rupture its DNA chain, making it unable to replicate itself, and the pathogen then dies.

Working on E.Coli, the E-beam can achieve 99.999% eradication of the bacteria in a fraction of a second, using less than a two kilogray dose. Anthrax is tougher to kill. It requires a dose of higher than 40 kilogray to remove all but a virtually incalculably small chance of any bacteria surviving. While the beam remains constant, the speed of the conveyor controls the dose-so the slower the belt moves, the greater the dose.

E-beams are particles, and can go through only two to three inches of a material like paper. For that reason, postal sterilization uses one linear accelerator set up above a conveyor system to destroy Anthrax at the top, and another underneath the conveyor to irradiate the reverse side. "You don't want to turn the package over to get to the other side with something as deadly as Anthrax," says Wil Williams, vice president of corporate communications for SureBeam.

For thicker packages, the Post office has purchased X-ray sterilization equipment from Ion Beam Applications (Oak Park, IL).

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