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Last Updated

27 Nov 2002

Source: New York Times, May 9, 2002.

Postal Theory: Mail Sorter Acted as Mill for Anthrax


Postal investigators say a chance extra run through sorting machines by the anthrax-tainted letter sent last fall to Senator Patrick J. Leahy may explain why its clumps of spores were smaller and more dangerous than those in a letter mailed the same day to Senator Tom Daschle.

The high-speed machines, which handle up to 550 letters a minute, could have acted like a mill, crumbling the microscopic clumps of deadly spores into smaller and more floatable bits with each pass, said an investigator involved in the hunt for the anthrax mailer who killed five people last fall.

"The Leahy letter was definitely handled by machines an extra time," he said.

But federal law enforcement officials, who recently disclosed the discrepancy in the size of the anthrax particles, called the postal investigators' theory possible but unlikely. "There's no enthusiasm for that theory," an official said. "Mail processing would probably not be effective."

Instead, the Federal Bureau of Investigation suspects that whoever prepared the anthrax put material of different grades in the two envelopes, officials said.

Only the smallest particles of anthrax spores are likely to penetrate deep into a person's lungs, where they can start an infection.

Postal inspectors said the letter to Mr. Leahy, the Vermont Democrat who is chairman of the Senate Judiciary Committee, made a side trip to the State Department after it was mailed in Trenton on Oct. 9 along with the letter to Mr. Daschle, the Senate majority leader. The sorting machine in Trenton that translated the handwritten address on the Leahy letter into a digital bar code made a mistake, turning 20510-4502 into 20520-4502.

After both letters passed through machines in the Brentwood sorting center that serves Washington, the Leahy letter was trucked to a separate sorter at the State Department, while the Daschle letter went straight to Capitol Hill.

Many officials have said the detour by the Leahy letter could explain why a State Department mail handler (case 20) developed inhalational anthrax. (He recovered.) But this is the first time officials have said the detour may also explain the extra level of potency in that envelope.

Each machine "has a series of belts that take a letter and pinch it, compressing any anthrax," the postal investigator said, adding: "The more times it goes through a piece of equipment, it refines it. That's the most likely explanation" for any difference in the contents.

The official acknowledged that there was still no hard evidence to support the theory.

Some bioterrorism experts have also raised the possibility that mail sorting could explain the smaller size of the clumps of spores in the Leahy anthrax. "It could be an additional process of milling, like a mortar and pestle," said Ken Alibek, a former Soviet germ-warfare official who is now president of Advanced Biosystems, a consulting company in Manassas, Va.

In the absence of new forensic clues, the investigation has fallen back on traditional shoe-leather methods.

In one effort, F.B.I. agents and postal inspectors have visited hundreds of households that received letters mailed through the Trenton sorting hub around the same time as the two letters to the senators.

The goal, postal inspectors said, is to get people to remember where the mail came from. This way, they might be able to trace which neighborhood the particular bin of mail that included the two poisoned missives came from.

With 47 post offices and about 700 blue collection boxes feeding mail into the sorting center, "that's a big universe," a postal inspector said.

Potentially telltale mail was identified using masses of computer data recorded as each letter entering the highly automated sorting centers is scanned for an address, given identifying bar codes recording its time and place of posting, and sent on its way.

The data include digital images of almost every hand-addressed envelope, which optical scanners cannot easily read, postal officials said.

Postal inspectors focused on mail that sped through the hub within minutes of the letters to the Capitol.

"The theory is that there'd be a clumping of mail," a postal inspector said. "In a collection box you'd think it'd have a tendency to kind of stay together."

The effort, at least initially, is paying off, he said. "Some patterns have definitely developed around both letters," he said, but he and other investigators declined to be more specific.