Logan Township, N.J. ? That letter to your congressman takes a curious detour these days, a 115-mile road trip to a sprawling industrial park in southern New Jersey.

In a ritual that has outlived the anthrax scare that prompted it, 9,000 pounds of mail addressed to congressional offices and federal departments — letters, petitions, invitations, junk mail, photographs, grant applications, newspaper clippings — arrive here each day to be exposed to enough radiation to neutralize any germs that might be lurking.

The process costs the government about $10 million a year and has altered how lawmakers keep in touch with the public. Many urge their constituents to e-mail, fax or call rather than send mail, which can arrive slightly burnt, melted or foul-smelling.

Though government contractors are working to develop mail-handling machines that continuously test for anthrax, “I can tell you that radiation is going to be in our future,” said Rep. Bob Ney, R-Ohio, who oversees mail as chairman of the House Administration Committee.

Irradiated mail is a lasting scar of the unsolved string of anthrax letters that paralyzed the postal system, and frightened the nation, weeks after the terrorist attacks of Sept. 11, 2001.

The anonymous mailings killed five people, sickened 17 others, and prompted thousands — including some members of Congress — to take a precautionary course of antibiotics.

Four known anthrax letters postmarked in Trenton, N.J., were sent to the New York Post, NBC News anchor Tom Brokaw, and the offices of Democratic Sens. Tom Daschle of South Dakota and Patrick Leahy of Vermont.

Two years later, nobody has been charged. A scientist identified by the FBI as a “person of interest” in the case, Steven J. Hatfill, has sued the government over its ongoing investigation and surveillance.

The Associated Press mailed two test letters to Capitol Hill from Washington on Aug. 27. One took nine business days to arrive; the other took 12.