TCS Daily

Battling Bioterror

By Noah Shachtman - November 22, 2002 12:00 AM

One of the few nice things about getting shot at is that you know when you're being attacked.

With biological strikes, there's no such luxury. Agents like anthrax can make you deadly ill before you're even aware of the assault.

So University of Wisconsin researchers are developing a radar-like system that can spot anthrax at a distance - providing some warning when a strange cloud, or a mysterious package, appears.

"The earlier you know, the more time you have to go button up your protective gear, or get the heck out of dodge," said John Bosma, a senior analyst with Synthesis Partners, a defense and biotechnology consulting firm.

The process is a new technique known as "terahertz imaging." And the idea is to bombard an unknown object with short pulses of extremely high-frequency electromagnetic waves. The patterns in which these waves are absorbed would say, for example, whether that suspicious white powder is
sugar or anthrax.

More than a year after a series of anthrax-laden packages were sent to the offices of Senator Tom Daschle and elsewhere, biological weapons remain a major concern, both at home and abroad. The anthrax mailer has yet to be caught. And Iraq reportedly has a stockpile of 1,800 gallons of anthrax, according to a recent Washington Times report. U.S. intelligence officials have become increasingly convinced that Saddam Hussein will use biological and chemical weapons on American troops if there is an attack on Iraqi soil.

But terahertz imaging won't be ready for a showdown with Saddam. In fact, the whole science of detecting and generating terahertz is only a decade or so old, according to John Federici, associate chair of the physics department at the New Jersey Institute of Technology.

Dr. Ingham Mack, with the Office of Naval Research, which is helping to fund terahertz research projects, said, "We're talking a couple of years... before it'll be able to detect biohazards on the battlefield."

Because current terahertz systems send waves out over a broad swath of the spectrum, there isn't enough power to send them more than about 10 meters, according to Wisconsin electrical engineering professor Daniel van der Weide.

A nearer-term application might be screening mail - without having to open the letters. In a recent experiment, van der Weide and his colleagues blasted 50 envelopes with terahertz waves. Some of the letters had common household powders. Others contained bacillus cereus, a relatively harmless cousin of the anthrax bacteria, used to kill butterflies. Van der Weide said the terahertz system was able to pick out the bacillus "well over 90%" of the time.

Terahertz imaging isn't the first attempt to spot toxins from afar. The military has been trying for decades to use the laser-light equivalent of radar to handle this task, David Siegrist, a research fellow with the Potomac Institute for Policy Studies, said.

But these LIDAR systems (short for "LIght Detection And Ranging") have had a difficult time peering through the naturally occurring organic materials in the atmosphere. The ultraviolet rays used to inspect a potential bioagent are easily absorbed by moisture in the air. (There's a similar limitation with terahertz). And LIDAR systems cannot distinguish between an actual pathogen - a disease causing agent - and similar, but harmless bacteria, noted Calvin Chue, with John Hopkins University's Center for Civilian Biodefense Studies.

It's unclear whether terahertz imaging will be able to make that distinction wither, Federici said.

He adds, "You're trading speed of recognition for specificity. You know there's a cloud of something in spore form coming at you. And you might have some time to protect yourself."



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