Anthrax is processed with silicon ("siliconized") to enhance its diffusion when exposed to air, thereby making it far more dangerous as a weapon.
Dr. Ivins did not have access to the equipment needed to siliconize anthrax. The samples recovered were weapons-grade anthrax that could only have come from a military weapons laboratory. The conclusion can only be that the terrorist(s) who sent the anthrax letters are still at large.
From page 18 and 19 of the report:
These tests and techniques allowed scientists to make several physical findings regarding
the Bacillus anthracis spores used in the letter attacks. The spore particles had a mass median
diameter between 22 and 38 microns. They exhibited an electrostatic charge, showed no signs of
genetic engineering, and were non-hemolytic, gamma-phage susceptible, antibiotic and vaccine
sensitive, and devoid of aerosolizing enhancers (e.g., fumed silica, bentonite, or other inert
material). These characteristics were and are inconsistent with weapons-grade anthracis
produced by offensive, state-sponsored biological weapons programs.5
Spore powder concentrations ranged from 4.60 x 1010 to 2.10 x 1012 colony-forming units
per gram, an extraordinarily high concentration. In addition, the spores in the Washington, D.C.
letters were of exceptional purity. Spores of such high concentration and purity indicate that they
were derived from high quality spore preparations. Spores of this quality are often used in bio
defense research, including vaccine development. It is important to have highly concentrated
spores to challenge most effectively the vaccine being tested. Similarly, highly purified spores
are necessary to prevent obstruction of the machinery used in those experiments.6 These findings
meant that the anthrax mailer must have possessed significant technical skill.
5
Throughout the course of the investigation, repeated challenges have been raised to this
finding that the spores were not weaponized. The challenges have their root in an initial finding
by the Armed Forces Institute of Pathology (”AFIP”) that, upon gross examination, the spores
exhibited a silicon and oxygen signal. However, subsequent analysis of the spores by Sandia
National Laboratories, using a more sensitive technology called transmission electron
microscopy (”TEM”) which enabled material characterization experts to focus its probe of the
spores to the nanometer scale determined that the silica was localized to the spore coat within
the exosporium, an area inside the spore. In other words, it was incorporated into the cell as a
natural part of the cell formation process. “The spores we examined lacked that fuzzy outer
coating that would indicate they’d been weaponized,” stated Dr. Paul Kotula of Sandia, who
personally examined the spores from the 2001 attacks. When presented with these results, Dr.
Peter Jahrling, a USAMRIID scientist who had reviewed the initial AFIP results and stated
publicly in late 2001 that the spores had been weaponized, retracted his earlier statement, telling
the Los Angeles Times on September 16, 2008, “I believe I made an honest mistake.”