New signs in California grocery stores and restaurants warn consumers, especially pregnant women and children, about the dangers of eating fish that contains mercury. But a battle is being waged over whether the warnings go far enough to protect the public.
Toxicologists agree that women of childbearing age and children should avoid swordfish, shark, king mackerel and tilefish and instead eat salmon, shrimp, sardines, catfish, scallops and other seafood with little or no detectable mercury.
But it is canned tuna -- by far the most popular seafood among American adults and children -- that has fueled a political and legal debate over mercury advisories in California stores and restaurants.
Many stores posted notices next to fresh and frozen fish in February, shortly after California Atty. Gen. Bill Lockyer sued seven grocery chains.
Lockyer alleges that the stores violated Proposition 65, a state law that requires businesses to post "clear and reasonable" warnings when exposing people to chemicals that cause cancer or reproductive harm.
The signs -- based on an advisory from the U.S. Food and Drug Administration and considered an interim measure at stores until the lawsuits are settled -- tell pregnant and nursing mothers, women who may become pregnant and young children to eat no swordfish, shark, king mackerel and tilefish.
They also are advised to "limit their consumption of other fish, including fresh or frozen tuna" and to eat no more than 12 ounces of various fish per week.
The signs give no specific advice about canned tuna, saying only, in smaller type, that "mercury levels in canned tuna vary, but on average are lower than levels in many other fish." No signs are posted in aisles where canned fish is sold.
Minus the mercury, fish, which contains omega-3 fatty acids, is a highly nutritious food that keeps hearts healthy.
The blood of one in 12 Americans exceeds the Environmental Protection Agency's "safe" level for mercury, according to data released in January by the Centers for Disease Control and Prevention. And among Californians, particularly upper-income residents, recent testing has found that high mercury levels are even more common.
Mercury is naturally found in the environment, but much of it also comes from coal-fired power plants and municipal waste-burning facilities. It settles in oceans and rivers and accumulates in predatory fish such as swordfish and shark that are large and long-lived.
A San Francisco physician, Dr. Jane Hightower, began sampling patients in 2000 and discovered that nine out of 10 of her patients had levels of mercury in their bodies that exceeded the EPA's recommendation. Hightower's findings were published in November in a study in the journal Environmental Health Perspectives.
Hightower, who tested more than 200 patients, decided to do so after she and a dermatologist colleague stumbled upon mercury while they were trying to figure out why a patient's hair was falling out. Hair loss is a symptom of mercury poisoning.
Hightower conducted a survey of her patients' diets and eventually concluded that fish bought in stores and restaurants was the source of the mercury.
On average, a swordfish steak or piece of shark contains about six times as much mercury as the same quantity of canned tuna, 2001 data from the FDA indicate. But because people eat much more tuna than any other fish, the bulk of the mercury in a person's body could come from canned tuna.
Hightower said the Proposition 65 signs and federal advisories are a good first step, but that better efforts are needed to send the right message to fish-eaters. The California Medical Assn. passed a resolution in March calling for notices wherever fish is sold, including labels on canned tuna.
"I was glad to see the signs go up," Hightower said. "People may just lean over the counter and ignore them, but at least the information is available and a lot more conspicuous."
Still, she said, the signs are too general. "What if people decide to eat grouper or lobster or canned albacore tuna?" which she said can have more than 1 part per million of mercury. "We need education on all the fish."
The tuna industry, however, is vigorously opposed to warnings that specify its products. Star-Kist Seafood, a division of Del Monte Foods, has asked grocery stores to keep warnings out of canned-food aisles, and the U.S. Tuna Foundation is campaigning to keep federal advisories from targeting canned tuna.
The Tuna Foundation, representing processors and marketers, says that "canned tuna has only trace amounts, well below all safety levels" and "continues to be a safe, convenient, affordable and delicious source" of protein, vitamins and nutrients.