Remember the post 9-11 anthrax was highly milled and that we didn't think Iraq had that refined capability.
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So whoever was responsible for last fall's bioterrorism wouldn't have needed to add silica to his anthrax powder at all. But he -- or she, or they -- might have had use for it while manufacturing that powder to begin with. Before they were kicked out of Iraq for good, U.N. weapons inspectors concluded that Saddam's military biologists were no longer relying on mechanical milling machines to render dried-out paste-colonies of anthracis bacteria into fine dust, but had instead refined a spray drying technique that produced the dust in a single step. And the suspected key ingredient in this Iraqi innovation, interestingly enough: pharmaceutical-grade silica, a common industrial drying agent.
4) But last fall's anthrax was milled mechanically, so it can't have come from Iraq, right?
We don't know that it was milled, really. Published reports conflict on this point, and those news accounts that do suggest the anthrax was milled invariably attribute the intelligence to federal investigators impressed by the super-granulated quality of the Leahy sample. In fact, evidently concerned that the Leahy letter might thus tend to confirm the Barbara Hatch Rosenberg conspiracy theory at its most rococo (i.e., that someone walked the anthrax straight out of a CIA lab), certain "government sources" have lately begun putting out word that the stuff was actually too good to be American. Two weeks ago, an item in Newsweek described a "secret new analysis" said to be circulating through high-level Washington, according to which analysis the Leahy letter's powder was "ground to a microscopic fineness not achieved by U.S. biological weapons experts." Researchers have found evidence of "intense milling," Newsweek explained: individual, free-floating anthracis spores, something our own government's scientists have "never seen" before.
But that's absurd. Individual, free-floating anthracis spores are what those scientists look at every day. And it's hardly a secret. During a December 15 Centers for Disease Control-sponsored conference on post-exposure prevention of inhalation anthrax -- you can find the transcript on CDC's website -- Dr. Louise Pitt of USAMRIID discussed in considerable detail how her colleagues at Ft. Detrick do their anthracis research. The spores, she said,
"are diluted to the desired concentration in sterile distilled water, water for injection. Our aerosols are extremely well characterized and defined. The particle size of the aerosol has a mass-meeting-aerosol diameter between .8 and 1.4 microns. That means that the aerosols that we are generating are basically single-spore aerosols. There's very, very little clumping of two spores. They are single-spore aerosols."
And remember, Ft. Detrick does not employ a mechanical milling process. Because, as it happens, people like Dr. Pitt have discovered much easier ways to make what our experts persist in calling the Leahy letter's "weapons-grade" anthrax: If they want it in a mist, they dilute the spores in water, as USAMRIID does. And if they want their anthrax dry, in a powder, they run it through what is essentially a very fancy flour sifter, a device commercially available throughout the world. This practice, too, has been specified in the open literature. A "Risk Assessment of Anthrax Threat Letters" published last year by Canada's Defence Research Establishment Suffield (DRES), for instance, was based on a bacterial specimen prepared in the "routine manner." Agar-grown cultures were dried into a "clumpy, undistinguished mess." And the mess was then filtered with a sifter, separating the largest chunks and leaving behind a final powder containing "a high proportion of singular spores."
Under a microscope, of course, singular spores, both milled and unmilled, look exactly the same.