Masks known as "respirators" or dust masks are much better at keeping germs out than surgical masks, says Frank Myers, an epidemiologist with Scripps Mercy Hospital in San Diego. That's because surgical masks are designed to keep doctors and nurses from infecting patients, not the other way around.
"The big difference is that if you wear a surgical mask, about 20 percent of the air you breathe in will be sucked in through the side of the mask, compared to a respirator, where none will sneak in," Myers says.Even the respirator masks, however, come with a price. They're bulky, hot and uncomfortable. To make matters worse, they're "virtually useless" if worn improperly, warns James Vincent, an expert in anthrax transmission and chairman of the Department of Environmental Health Sciences at the University of Michigan School of Public Health.
Experts agree, however, that masks are important barriers to anthrax bacteria. Even though anthrax germs are encased in protective spores, they are still tiny, as little as one micron -- one-thousandth of a millimeter -- across. And they can lie in wait for months or years; they don't die quickly in the air like other germs.
Anthrax bacteria remain in a kind of suspended animation -- more dead than asleep -- until they find themselves in a friendly environment, like a human body, says Tom Reilly, a biology professor at Ball State University. Then the bacteria come back to life and begin wreaking havoc on the body, especially in cases of anthrax that are inhaled or eaten.
Although some scientists and government officials have made estimates, no one knows how many anthrax spores are enough to cause illness. Federal researchers working with the most volatile forms of the bacteria are extremely cautious and must take the same precautions as they do with the virus that causes AIDS. Only a few other diseases, such as Ebola, require more security.
The inhaled form of anthrax is the most serious because it works its way from the lungs into the immune system, spreading toxins throughout the bloodstream. The mildest form of anthrax is known as cutaneous and is contracted when spores enter the body through openings in the skin, such as scrapes.
To protect its employees from cutaneous anthrax, the U.S. Postal Service has purchased 90 million pairs of gloves made of a plastic substance known as Nitrile. Each worker will get several pairs of gloves to wear each day.
"Gloves will be helpful in protecting against anthrax if you don't touch your face with your gloved hands," says Dr. Don Milton, a lecturer on environmental health at the Harvard School of Public Health. But many anthrax infections are on the face and neck, so handwashing and good hygiene will remain important, Milton says.
The Centers for Disease Control and Prevention recommends that gloves be impermeable, although cotton gloves may be worn under protective ones for comfort and to protect against skin allergies. Latex gloves aren't recommended.
In addition, the U.S. Postal Service is providing 4.8 million respirators to employees who want them. The respirators are certified to filter particles as tiny as 0.3 microns, much smaller than anthrax spores.
According to online merchants, respirators cost less than $1 each. They must be expertly fitted to protect against fine particles in the air, such as germs, Vincent says. "The biggest single problem is the fit of the mask. If it fits poorly, if there are spaces around the face and around the mouth and nose, then the particles will take the path of least resistance and not pass through the filter material."
Even if they are fitted correctly, users may find masks to be a hassle, says Milton of the Harvard School of Public Health. "Respirators are hot and uncomfortable and very difficult to wear for hours on end, especially while lifting and carrying. These activities tend to cause breaks in the face seal and reduce the effectiveness of the respirator."
Instead of relying on devices to protect employees, the U.S. Postal Service should make sure that the air in post offices is properly filtered and ventilated, he says.
What To Do
Respirators and gloves may make employees feel better and provide some protection against germs in the mail. But make sure you buy the appropriate kinds. The Centers for Disease Control and Prevention offers this guide to mailroom safety.
Learn the basics about anthrax from the Johns Hopkins Center for Civilian Biodefense Studies.