The anthrax spores in the letters seem to have undergone the same
鈥渨eaponisation鈥� technique used to make US bioweapons in the 1960s, a source who
cannot be named told 麻豆传媒 this week.
This involves treating anthrax cultures with chemicals that make them break
into small clumps of spores as they dry, allowing them to stay separate,
airborne鈥攁nd inhalable. While terrorists in several countries might have
obtained the Ames strain, the US鈥檚 weaponising recipe is supposed to be a
closely guarded secret. If the anthrax has indeed undergone US-style
weaponisation, then either the secret is out or the attacks are being made with
leftovers from the American weapons programme.
Analyses of the anthrax have focused on the largest sample available, from
the envelope sent to Senator Tom Daschle. These particles are between 1.5 and 3
micrometres across, and contain the drying agent silica but no traces of the
anticaking agent the Iraqis tried to use without success. The Soviets did
succeed in making dry anthrax, but their milling process reportedly yielded
particles with a wider size range.
Advertisement
The spores found in ventilation filters in Washington DC postal offices, and
the growing number of cases in postal workers, also support the idea that the
anthrax was treated to help it spread through the air. Half of the 16 victims so
far worked for the US Postal Service.
