The dry powder used in the anthrax attacks is virtually indistinguishable in critical technical respects from that produced by the United States military before it shut down its biowarfare program, according to federal scientists and a report prepared for a military contractor.
The preliminary analysis of the powder shows that it has the same extraordinarily high concentration of deadly spores as the anthrax produced in the American weapons program. While it is still possible that the anthrax could have a foreign source, the concentration is higher than any stock publicly known to be produced by other governments.
The similarity to the levels achieved by the United States military lends support to the idea that someone with ties to the old program may be behind the attacks that have killed five people. The Federal Bureau of Investigation recently expanded its investigation of anthrax suspects to include government and contractor laboratories as a possible source of the deadly powder itself, or of knowledge of how to make it.
Its high concentration is surprising, weapon experts said, and far beyond what military analysts once judged as the likely abilities of terrorists. Still, experts caution that the emerging evidence is tentative and that it is too early to rule out other possible suspects, be they domestic lone wolves or hostile foreign states like Iraq.
A yardstick for measuring the quality of anthrax emerged almost three years ago when William C. Patrick III, a longtime federal consultant and one of the nation's top experts on biological weapons, wrote a report assessing the possible risks if terrorists were to send anthrax through the mail. Based on the difficulty of developing advanced anthrax, he predicted that the terrorist germs would be one-twentieth as concentrated as what the government developed and what has recently turned letters into munitions.
"The quality of the spores is very good," said a federal science adviser who shared the Patrick report with The New York Times . "This is very high-quality stuff" — equal, he said, in concentration to that produced by the United States military before it abandoned germ weapons.
The high quality, the adviser said, lends credence to the idea that someone with links to military laboratories or their contractors might be behind the attacks. "It's frightening to think that one of our own scientists could have done something like this," he said. "But it's definitely possible."
He said the anthrax sent to the Senate contained as many as one trillion spores per gram, a figure confirmed by an administration official.
A gram is just one-twenty-eighth of an ounce. Yet in comprising up to one trillion spores, a gram of anthrax powder has vast potential to kill. If a lethal dose is estimated conservatively at 10,000 microscopic spores, then a gram in theory could cause about 100 million deaths.
The letter sent to Tom Daschle, the Senate Democratic leader, is said to have held two grams of anthrax — enough, in other words, to make about 200 million lethal doses, assuming it could be distributed to victims with perfect efficiency.
Analysis of the Daschle powder has been hampered by the small amount recovered after an aide opened the letter, and by technical missteps as the investigation got under way, making some conclusions iffy. That is why investigators are taking great care in opening the anthrax-contaminated letter sent to Patrick J. Leahy, chairman of the Senate Judiciary Committee. The aim is to scrutinize the evidence as closely as possible.
Spore concentration is just one factor experts will examine in the Leahy letter, and their findings could significantly alter their picture of the powder. Other factors that reflect the quality of anthrax production include whether the powder has been ground to a size that easily lodges in the lungs and whether it has been treated to make it static free and free-floating. Investigators will look for antistatic additives that might be a possible hallmark of a particular government's weapons program.