Canned tuna manufacturers should have warned consumers about the potentially toxic mercury levels in their products, said California Attorney General Bill Lockyer in a suit filed June 21 against the makers of StarKist, Bumble Bee and Chicken of the Sea tuna.

California's Proposition 65, in effect since 1986, requires manufacturers to warn consumers if their products contain known carcinogens or reproductive toxins. Mercury and methylmercury have been known since the late 1980s to cause cancer and reproductive difficulties. "Prenatal exposure to mercury can cause serious disabilities in infants and children," such as mental retardation, cerebral palsy, deafness, blindness and developmental disabilities, Lockyer said.

In March 2004 the U.S. Food and Drug Administration and the Environmental Protection Agency advised consumers to limit fish and shellfish consumption to 12 ounces per week, or 6 ounces for adolescent girls and women of childbearing age.

Lockyer's office tested albacore and light canned tunas for sale in California and found that both varieties have higher levels of mercury than is generally deemed safe.

"The levels of mercury in canned tuna that are sufficient to trigger the requirement to post a Prop 65 warning are substantially lower than for, quote unquote, "safe exposure,'" said Tom Dresslar, a spokesman for Lockyer's office. Nonetheless, the AG's tests found levels that exceed both Proposition 65 levels and those established by the FDA and EPA in March.

"We're not trying to eliminate tuna from people's diets. We're trying to enforce the law and protect the health and safety of California women and children," Lockyer said in a news release.

Added Dresslar, "People need to be fully informed about how much canned tuna they eat, especially if they're in the at-risk categories."

Physicians for Social Responsibility, a nonprofit group of more than 24,000 members nationwide, takes a similar stance. "We don't think the FDA/EPA guidelines go far enough in protecting women and children," said Susan Marmagas, director, environment and health program for PSR. The group, along with the Association for Reproductive Health Professionals, has released a brochure and wallet guide for consumers that helps them balance decisions about eating fish for their health.

If the California suit is successful, the companies involved—Del Monte, Bumble Bee Seafoods and Tri-Union Seafoods—would be liable for fines up to $2,500 per day for each violation, dating back to 2000. The suit also would require tuna companies to post warnings on can labels or store signage.

The U.S. Tuna Foundation holds that manufacturers should not be liable because the mercury occurs naturally in deep-water fish. According to a USTF news release, Proposition 65 pertains only to substances that manufacturers add to their products, rendering the suit unwarranted. "This suit is not grounded in science and will needlessly scare consumers away from affordable foods that are good for them," said David Burney, USTF executive director.

"They have the burden of proving that in the Prop 65 litigation," Dresslar said. "We don't think it's a burden they can meet." Besides, he added, "There's plenty of evidence out there that shows a substantial part of the mercury exposure comes from manmade sources."

California is the only state that has this kind of law, Dresslar said, so it's unlikely to affect consumers or retailers in other states.

But other observers say that costs for canned tuna could go up across the board as a result of the suit. Manufacturers would have to spend money to make sure that the cans with warning labels don't make it to stores outside of California, and would likely recoup that cost at the cash register.