ARLINGTON, Va. (AP) -- Thousands more workers than first thought could face serious health threats from exposure to plutonium and other highly radioactive matter that fouled a large amount of uranium recycled by U.S. nuclear weapons programs, a published report says.

From 1952 until 1999, when the shipments ended because of the contamination threat, vast quantities of recycled uranium were shipped worldwide.

New government studies, reviewed by USA Today and reported in Monday's editions, found that the recycling program yielded 250,000 tons of tainted uranium, or about twice as much as earlier estimated. The highly radioactive material was handled at about 10 times the number of sites previously revealed and reportedly reached more than 100 federal plants, private manufacturers and universities.

"This stuff circulated much more widely than we'd thought," said Robert Alvarez, an official at the Energy Department when the new studies were started in 1999.

USA Today said the latest studies suggest that thousands more workers than expected might have unwittingly faced radiation risks beyond those associated with normal uranium. That exposure could significantly increase their odds of developing cancer and other diseases.

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