Roberge's idea for his Pennsylvania Junior Academy of Sciences project -- which won first place at regional and state events last year -- came after the 2001 bioterrorism attack in which letters containing anthrax spores were mailed to several news media offices and two U.S. senators. Anthrax infections killed five people. The crimes remain unsolved.

Anthrax mail scares still occur periodically. Last week, a letter containing a mysterious white powder and addressed to Americans triggered an anthrax alert at a NATO center in Norway, the Associated Press reported.

Anthrax spores, covered by a hard protective shell, can fatally infect people who inhale them deep into the lungs.

On Oct. 12, 2001, a former Soviet germ warfare specialist told members of a U.S. Congressional committee that people could use a hot steam iron through a moist layer of fabric to kill anthrax spores in mail.

This comment spawned debate about whether conventional household irons would work against the deadly agent. During a CNN interview four years ago, a reporter asked Dr. Roberge if the report was accurate.

"My response was to her was that high heat could kill anthrax, but I didn't know if a household iron would work, since no studies had been done," he said.

Roberge discussed the topic over dinner that night with his son, who decided to investigate it for his Academy of Sciences project, required as part of his Advanced Placement biology course.

For his experiments -- conducted in the family's Highland Park home and at Central Catholic in Oakland -- Marc Roberge did not use actual anthrax.

"The government might have had a little problem with that," he said.

Instead, he substituted a more heat-resistant but harmless bacterial spore from the anthrax family that scientists often use as a surrogate.

Marc Roberge placed paper strips laden with millions of spores inside standard envelopes, and then ironed the mail at various dry heat settings for up to 15 minutes.

He found that an iron adjusted to the hottest setting -- at least 204.5 degrees Celsius, or 400 degrees Fahrenheit -- and used for at least 5 minutes destroyed all spores so no bacteria would grow. The iron didn't open the letters or make pen-written addresses hard to read, Roberge said.

"When the anthrax attacks happened, I thought, 'There's got to be a way to stop this,'" he said. "I just never thought it would be so easy."

Based on Roberge's findings, University of Pittsburgh Medical Center bioterrorism expert Dr. Michael Allswede doesn't recommend that people routinely press their mail.

"But should there be another threat like the anthrax attacks in 2001, it would be one of the techniques that could be used by regular people," he said.