When: In 1997 the FDA approved the use of irradiation for red meat and meat products, while opponents said more studies needed to be done.
Why: The FDA and meat producers said irradiation would help reduce the bacteria that causes food poisoning, but opponents pointed to studies linking irradiated meat to elevated levels of cancer.
The FDA requires that irradiated foods sold in stores be marked and carry the international symbol for irradiation. But some supermarkets, such as Whole Foods Markets, are reluctant to carry irradiated meat and other irradiated products.
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Last updated July 16 2008: 10:50 AM ET