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Bio-terrorism alarmists view last week’s death of a Florida man from anthrax as validation of their advocacy of panic. Cooler heads view the incident more as a limited bio-crime rather than a harbinger of mass bio-terrorism.

Such skepticism no doubt arises from the often glossed-over difficulty of using anthrax as a weapon of mass bio-terror.

Anthrax is a bacterium that may cause death by inhalation, ingestion or by contact with skin. The most lethal form of exposure is inhalation of anthrax spores—bodies serving as vehicles for the bacterium.

Alarmists say, "One billionth of a gram (of anthrax), smaller than a speck of dust can kill." But one anthrax spore, even thousands of spores, will not kill anyone.

Wool sorters inhale 150 to 700 anthrax spores per hour continually without danger. Laboratory studies indicate that about 10,000 spores are necessary to start an infection by inhalation.

As with other toxins, it’s the dose that makes the poison. Therein lies the chief difficulty for anthrax as an effective mass terror weapon.

The technical hurdles and related expenses associated with exposing many people to enough anthrax is daunting.

Aum Shinrikyo, the well-financed terrorist group that used nerve gas in the Tokyo subway in 1995, learned this lesson firsthand. The group employed scientists and invested a great deal of money in trying to develop anthrax into a weapon of mass destruction. The effort failed.

Anthrax spores are easy enough to obtain. But before spores can be made into a mass inhalation threat, they need to be converted to a powdered form. Liquified anthrax would fall to the ground and be ineffective.

In contrast to producing spores, "powderizing" anthrax is no trivial task.

Even assuming would-be terrorists had the technical know-how for producing mass quantities of powdered anthrax—without killing production workers and surrounding populations—the necessary facilities and development would cost hundreds of millions of dollars. Purchasing a few unemployed, ex-Soviet bio-weapons experts is not enough.

Not surprisingly, only the U.S. and Russia so far have succeeded in powderizing anthrax for purposes of weaponry.

Iraq is the most expected source of mass anthrax bio-terrorism. But Iraq only has anthrax in liquid form.

Even Iraq seems to know that its liquefied anthrax is virtually useless. United Nations inspectors found relatively few Iraqi warheads containing anthrax. If Iraq had an effective form of anthrax, it would likely have been found in many more warheads—like the many Iraqi warheads containing nerve gas.

Iraq probably will never have anthrax capability. As Jane’s Intelligence Review reported, "… the Iraqis would have to maintain rigorous First World standards and not their usual ‘make do’ efforts."

Powderizing anthrax is not the end of the challenge.

Once released into the air, spores then become subject to atmospheric conditions. Too much wind will disperse spores into harmless concentrations. Not enough wind, the spores will fall to the ground and not arise again in harmful concentrations.

Airplanes dusting a city would be an unlikely choice for spreading anthrax spores. The few spores entering buildings would mostly settle; the few that didn’t would likely be insufficient in concentration to cause infection. Outside, spores would likely fall to the ground or be blown away and rendered essentially harmless.

If enough spores were dropped, some people conceivably may inhale enough to become infected. But in the worst-case, this might happen to dozens, rather than thousands of people. An accidental release of anthrax spores at a Soviet bio-weapons laboratory in 1979 resulted in about 70 deaths in a metropolitan area of about one million people.

In reckless disregard for the prospects of mass anthrax terrorism, American Public Health Association executive director Mohammmad Akhter wrote in the Washington Post this week, "A cloud of anthrax spores drifting over Arlington (Virginia) could kill tens of thousands of Washingtonians within days."

Then there’s University of Minnesota epidemiologist Michael Osterholm who told 60 Minutes last Sunday that, "What is important is to scare people into positive action."

Here’s the real problem that might hit the U.S. in the next couple of months because of this "scaring people into positive action."

Flu season is near. Anthrax infection initially resembles the flu. Physicians and the public are being told not to assume that flu-like symptoms indicate the flu. Anthrax infection should be suspected as well, say the alarmists.

Perhaps more than 100 million people in the U.S. will exhibit flu-like symptoms at some point during this flu season. Should every cough, sore throat, runny or stuffy nose, and headache be treated as a possible case of anthrax infection?

Only if we want to bring our public health system to a grinding halt.

We are—and always will be—vulnerable to limited anthrax attacks, whether by bio-crime or bio-terrorism. We should minimize and contain these attacks with the sort of rapid response now being exercised in Florida.

But since mass terror with anthrax is improbable, terrorizing the masses is probably unwise.

Steven Milloy is the publisher of JunkScience.com, an adjunct scholar at the Cato Institute and the author of Junk Science Judo: Self-defense Against Health Scares and Scams (Cato Institute, 2001).