Last week, food giant Del Monte (NYSE:DLM) spoke of rising sales for Star-Kist Tuna Creations -- a high-end, high-margin tuna product. This week, a unified EPA and FDA Food Advisory Committee warning advised "pregnant women, nursing mothers, woman who may become pregnant, and young children" to limit their tuna consumption.

Mercury (really methylmercury) is a neurotoxin that affects the development of the brain and nervous system. The FDA has warned for years that mercury is found in high concentrations in shark, king mackerel, and tilefish -- and, now, tuna. Some tuna is more contaminated than others: Albacore (white meat tuna) has nearly three times the mercury of light meat tuna.

Del Monte expected sales in 2004 to grow 2% to 4%, and earnings to grow 6% to 9%. As Carla Pasternak noted last week, "Star-Kist tuna's U.S. market share had already dropped 9% in the five years before Del Monte took over the brand. If Heinz and all its financial muscle couldn't turn around these brands, it takes a giant leap of faith to believe that a company like Del Monte will."

Now, with the EPA and FDA on the scene, "Sorry, Charlie" may take on a whole new meaning.

Heinz (NYSE:HNZ) shareholders thinking they dodged a bullet by selling Star-Kist to Del Monte are only partly right. Outside the U.S., Heinz owns John West Foods, Petit Navire, and Greenseas -- all leading tuna brands. And other countries are concerned about tuna, too. Health Canada already warns against eating fresh or frozen tuna more than once a week -- and once a month for children and pregnant women.

ConAgra (NYSE:CAG) shareholders, on the other hand, may indeed be relieved to have unloaded Bumble Bee earlier this year. After all, Bumble Bee has 40% of the U.S. albacore market.

What comes of the FDA/EPA advisory is not clear. If consumers switch to arguably healthier meats, like chicken, Tyson Foods (NYSE:TSN) could benefit. With canned tuna such a popular take-to-work lunch, Campbell Soup's (NYSE:CPB) might pick up some slack. Even the fast food kings McDonald's (NYSE:MCD) and Yum! Brands (NYSE:YUM) may find their own menu items selling in higher volumes.

On thing's for certain, this mercury scare has tuna sellers hot under the collar.

Besides being a tuna lover and feeding 9Lives tuna to his cats, W.D. Crotty used to work for Star-Kist. You can e-mail W.D. at wdcrotty@fool.com.