New Questions Raised on Anthrax Perils

Study Finds Spores in Daschle Office Easily Stirred Up, Complicating Risk Questions

By David Brown, Washington Post Staff Writer

DECATUR, Ga. -- The anthrax spores that settled on floors and desks in Senate Majority Leader Thomas A. Daschle's office can be stirred up and made airborne again much more easily than had been thought possible, researchers reported yesterday in a finding that could help explain why the powder was so dangerous.

The observation that the spores are readily "reaerosolized" also suggests, at least theoretically, that offices, postal buildings and other areas contaminated with the microbes could remain health hazards long after the initial event in which the bacteria was released.

Based on research conducted decades ago, investigators probing this fall's anthrax attacks had assumed it would be difficult for someone to become infected with spores once they landed on a surface. But researchers began to reconsider that assumption after evidence emerged that women who died from anthrax in Connecticut and New York might have become infected from mail that had picked up spores by going through contaminated postal equipment.

The new research indicates that the spores spread in the recent mail attacks do in fact behave differently from those studied before, mostly in outdoor simulations of germ warfare.

At a meeting convened here by the Centers for Disease Control and Prevention, two government scientists gave a preliminary report on their experiments in Daschle's Capitol Hill office, which was heavily contaminated when a letter containing powdered bacteria was opened there in October.

"I think everybody hoped that they wouldn't be aerosolized, but it does seem they are able to be," said Christopher P. Weis, a toxicologist with the Environmental Protection Agency (EPA) who headed up the study.

"Is there something different about the environment, or something different about these spores? Those are some of the things we're trying to figure out," said Aubrey K. Miller, a physician and epidemiologist with the U.S. Public Health Service.

The numbers of spores put into the air was small. However, nobody knows what a truly "safe" dose of inhaled anthrax bacteria may be, which makes it hard to know what to make of the results, the researchers said. The Daschle office was recently decontaminated, and follow-up testing is being done to see whether any viable anthrax spores remain.

The Centers for Disease Control and Prevention convened the two-day meeting to draw up a list of the most urgent priorities for anthrax bioterror research. About 100 scientists from universities, government agencies and the military are attending.

The letter sent to Daschle (D-S.D.) contained finely ground particles. Twenty-eight people in and near the room where it was opened had spores in their noses immediately afterward, suggesting the powder floated easily and dispersed rapidly.

The room, on the sixth floor of the Hart Senate Office Building, was sealed for almost a month, before Weis and several colleagues entered it in the second week of November. They each wore two plastic oversuits, and breathed filtered air.

In the first half of the experiment, they placed 17 culture bacterial plates around the office, eight on the floor and nine on chairs. The researchers moved slowly and tried to disturb the environment as little as possible. An hour later, they retrieved the plates.

In the afternoon of the same day, they returned and put out another 17 plates. This time, though, three of them stayed and spent an hour doing office work -- walking around, sorting and opening mail, shuffling papers, changing paper on the fax machine. Then, as in the morning, they sent the culture plates to the laboratory.

Out of the 17 plates placed during the quiet period, five grew Bacillus anthracis, the bacterium that causes anthrax. Furthermore, there were only a few bacterial colonies on the positive plates. (One colony represents the landing of a single spore-containing particle.)

Out of the 17 placed during the working period, however, 16 grew the bacteria, Weis said. On at least one, there were 20 colonies.

The researchers also sampled the air directly during the experiment, using simulated breathing devices placed at both floor level and desk level. A small number of spores were picked up during the quiet period, and many more -- in one case, a hundred times more -- were detected during the working period. The quantification of this part of the study is still going on.

The question of what dose of anthrax spores is needed to infect a person is especially important, as it touches on many decisions public health officials must make. Those include when to consider a contaminated place hazardous; when to advise exposed people to take preventive antibiotics for 60 days, and whether an environment must be sterilized to be considered safe.

At today's meeting, Philip Brachman, formerly with the CDC and now with Emory University, recounted the perplexing picture of inhalational anthrax gleaned from the fewer than 20 cases reported in the United States in the last 75 years.

On the one hand, mills processing goat hair for use in suit linings and pipe insulation were often heavily contaminated, but outbreaks of disease were very rare.

On the other hand, some victims appeared to have only fleeting exposure to B. anthracis. One furniture factory worker died of inhalational infection in Philadelphia more than 50 years ago after he apparently became infected simply by walking by the loading dock of a tannery on his way to work.

Arthur Friedlander, an anthrax researcher at the U.S. Army's laboratories at Fort Detrick, Md., said his review of the old cases suggests that at least half the people had some underlying illness -- such as a lung disease or cirrhosis -- that may have put them at higher risk or blunted their immune systems. This may also explain some of the recent cases, such as that of a 94-year-old woman in Connecticut who appears to have been exposed to only a small concentration of spores.