B O S T O N, Sept. 27, 2001 -- Heightened concern of another possible terrorist attack, this time using biological or chemical agents, is driving many people to buy what they believe is their only protection — a gas mask. But experts question how effective they are and if they could be used in time.
"I believe individuals buying gas masks to protect themselves against an unspecified biological or chemical attack is pretty useless," says Dr. John Clements, professor and chair of Immunology and Microbiology at Tulane University.
Biologically the biggest threat is Anthrax, which Clements believes would most likely be released unrecognized into a populated area. So gas mask or not, some people may not even be aware of the attack.
"The infection takes one to six days to start showing symptoms, and you are not going to be aware that you were exposed for some time," he says, adding: "The potential for person to person spread is low."
Plus, Clements says, the chemical agents of greatest concern are nerve gasses, such as Sarin, for which even a gas mask does not give full protection.
"It is true that they are most effective when inhaled, but they are very effectively absorbed through the skin as well," he says. "In a closed environment, such as a building or a subway tunnel, high enough concentrations would be achieved to make a mask pretty much useless."
They Can Make Things Worse
Another problem with gas masks is, "They do not fit children," says Samuel Watson, director of the Biomedical Security Institute at the University of Pittsburgh School of Public Health.
Plus, "they may make people's heart or lung conditions worse, and some people [about 2 percent] are too claustrophobic to use a mask."
Experts also point out that there's more to using a gas mask than just putting it on. It's important to receive proper training and maintenance.
The charcoal filters break down with time, the gaskets deteriorate, and they must be the right size for the individual that plans to use them," explains Clements.
Plus, say the experts, even if it's working right, the mask has to be able to do the job it's meant for. Not all of them can block particles of the right size
"A 'gas mask' refers to a chemical absorbent air filtration system. The chemical absorbent, in most cases, is activated charcoal, and works like a sponge for chemicals," explains Dr. Michael Allswede, Toxicologist in the Department of Emergency Medicine at the University of Pittsburgh. To block out small particles, "a high efficiency particulate air filter (HEPA) is what is needed," similar to a surgeon's mask.
Various government agencies, including the Centers for Disease Control and the Defense Department, test gas masks to be sure they meet HEPA standards.
Because chemical and biological agents can spread very quickly, experts agree that for a gas mask to be effective, timing is everything.
"The issue is much less the mask than when to don it. In a chemical attack, you must have it at your side to make a difference," says Dr. Richard Moyer of the Department of Molecular Genetics and Microbiology at the University of Florida.
Dr. Mary Gilchrist, director of the Hygienic Lab at the University of Iowa, points out that wearing a gas mask all day is not practical.
Microorganisms would most likely be in the air without our knowledge, so the only way to protect oneself would be to wear the mask for 24 hours a day, seven days a week, and that, of course, would interfere with many activities.
Vaccinations May Help More
Moyer believes the best weapons we have to combat against biochemical warfare are vaccines — not gas masks.
"In the case of biologicals, particularly smallpox, probably the wisest long-term course would be to reinstitute smallpox vaccination, which is completely effective except for those rare complications which accompany any mass vaccination program."
"If the U.S. were globally vaccinated, this threat would simply disappear. There is considerable effort in place in the United States to redevelop a smallpox vaccine. There is also a vaccine for anthrax, but it has never been used on a scale that smallpox vaccination has."
ABCNEWS medical editor Dr. Tim Johnson said he wouldn't recommend that his friends or family in the United States stock up on gas masks, but he understands why some people might.
Johnson agrees with most terrorism experts who believe that while a biological or chemical attack could be devastating in theory, the logistics make it less likely that a terrorist could carry out a successful, widespread assault.
"If attacks occur, I think all the experts agree they're going to be in a very limited geographical area," Johnson said. "It's very hard to blanket the entire United States."
William Broad, author of Germs: Biological Weapons and America's Secret War, concurred, in a recent ABCNEWS.com chat:
"My own feeling is that we all have a greater chance of dying on the highway than of getting hit by anthrax."