Postal Service Weighs Using Radiation on Mail

U.S. postal officials are considering whether to use radiation technology to sanitize mail and mail facilities to defend against anthrax, and experts say a range of effective systems is available.

Radiation sanitizing systems are common in hospitals, where they are used to sterilize medical devices and kill airborne bacteria, and in the food and pharmaceutical industries. The systems rely on high-energy light beams that can kill viruses and bacteria.

A radiation system could be devised for sanitizing mail and mail-processing centers, several experts said. “I think it’s conceivable and practical,” said Gerry Reis, a senior vice president at Steris Corp. of Ohio, which sells sanitizing equipment and services.

Reis said he was in Washington for meetings about developing such a system. He declined to say with whom he was meeting.

The radiation systems used in the food industry to kill bacteria would be well-suited to sterilizing mail, said Jeffrey T. Barach, vice president for special projects at the National Food Processors Assn. He said the systems do not leave any residue and do not make the food or other items radioactive.

But which system the Postal Service chooses would depend on what it wants to sanitize--the outside of letters, the inside of letters, mail-sorting machinery or the air inside postal facilities.

It is unclear what kind of system they might select, because officials say they do not know yet how postal workers contracted inhalation anthrax.

Experts say anthrax spores may have shot through the creases of an envelope and into the air when a tainted letter passed through mail-sorting equipment. Another possibility is that a tainted letter was mangled by postal equipment, causing the contents to scatter into the air.

Or, anthrax spores may have dropped onto postal equipment from either the outside or inside of a letter, and then were circulated in the air by blowers used to clean mail-sorting machines. Since the anthrax cases surfaced, postal officials have moved to replace the blowers with vacuums, the preferred method for cleaning the equipment.

Melvin First, a Harvard University professor emeritus of environmental health engineering, said the government could use an ultraviolet light system to neutralize anthrax spores that sit on the surface of letters and postal equipment. Because the light can damage the eyes, workers using that system would have to wear protective glasses or have no contact with the light.

Ultraviolet light systems have been used to clean the air at hospitals and elsewhere. In one current experiment, First said, ultraviolet lights have been installed in five homeless shelters, where they shine above the heads of people in the buildings. The experiment is designed to study whether ultraviolet light can decrease the airborne transmission of tuberculosis.

To penetrate beneath the surface of a letter or package, a more powerful system using ionizing radiation would be needed, First said. That method would have other advantages. As a measure of how deep the rays can penetrate, First said, ionizing radiation has been used to draw images of the insides of boilers, which often have steel walls three-quarters of an inch thick.

Ionizing radiation is used frequently in the food industry, First said. “The Japanese, for example, love grapefruit but won’t get it from the U.S. unless it’s been sterilized, because they are terribly afraid of importing fruit flies,” he said.

At a news conference Monday, Postmaster General John Potter said he was focusing on ultraviolet light systems.

But Reis said ultraviolet light might be impractical to use in the postal system because the volume of mail is so high. He said ionizing radiation would work better because it could penetrate several layers of letters.

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The Associated Press was used in compiling this report.