Federal inspectors are checking all travelers arriving in the United States for radiation as part of an expanded effort to screen for terrorist activity, a customs official said Saturday.
Dean Boyd, a spokesman for the new Bureau of Customs and Border Protection, said inspectors began using small, pager-like detectors Saturday at U.S. ports of entry to check passengers for radiation.
He said the inspectors, who ask incoming travelers for their passports, carry the detectors on their belts.
"If a source of radiation passes close by or within a certain distance, the pager will begin beeping or alerting, and you can look down at the pager and see the amount [of radiation] that the pager is picking up," Boyd said.
U.S. Customs Commissioner Robert Bonner said there was no guarantee that the radiation screening and other increased security at U.S. borders would stop a terrorist, but the agency believes all measures must be employed.
Passengers may not notice the devices because inspectors do not have to sweep passengers with them to detect radiation, Boyd said. The pagers simply beep or vibrate to let inspectors know when a source of radiation is nearby, he said.
The goal is to screen all of the more than 500,000 people entering the United States every day. Inspectors who check passports at the arrival gates will carry them.
The government was using just 4,000 of the pagers before the Sept. 11 attacks but officials have now distributed more of the devices, bringing the total to 7,000, as Customs and nearly two dozen other federal agencies formally joined the Homeland Security Department.
The pagers cost about $2,500 each. Boyd said officials hope to distribute more of them so that all 9,000 customs inspectors will carry them.
Government auditors warned lawmakers in October that the pagers' range is too limited to be effective. Boyd said officials know all technology has its limits.
"The pagers -- they are not a silver bullet. They are one piece of technology that we use, and we use a broad range of technologies to detect radiation," he said.
The detectors can be set off by low levels of radiation, such as by people who might be undergoing chemotherapy or someone who recently had an X-ray. Potassium in bananas could also set off a detector.
As a backup, Boyd said, a few hundred of the inspectors have hand-held devices called "isotope identifiers," which signal what the radioactive material is.
"It allows us to determine whether it's a nuclear bomb or components for a dirty bomb," Boyd said.
A dirty bomb uses conventional explosives to disperse radioactive material.
The government has other equipment to check for radioactive weapons, such as special monitors that screen trucks. Even though customs officials hope to have 400 of them operating in less than a year, government auditors have said it will take years to get the equipment working properly and to train users.
The government also has 200 vans equipped with gamma ray machines that act like giant X-ray equipment for checking cargo containers.