Health officials have become uneasy about the growing demand for paddlefish caviar. A variety of toxins have been found in the fish eggs, including mercury, chlordane and cancer-causing polychlorinated biphenyls, or PCBs.

Kentucky, Indiana and Tennessee have issued advisories warning consumers to limit their consumption of paddlefish caviar from certain sources. But since the FDA does not require companies to list river of origin on labels, it can be difficult to know the source of caviar.

Linda Greer, health director for the Natural Resources Defense Council in New York, said consumers should avoid any foods containing PCBs. "There's no safe level of exposure to a carcinogen," she argues. "My advice would be to err on the side of caution and not eat the paddlefish caviar."