The findings suggest that a typical grocery-store shopper has a 50 percent chance of buying a swordfish steak with mercury levels considered unsafe by the FDA.

Mercury is a dangerous neurotoxin that has been linked to learning disabilities and developmental delays in children, as well as damage to the heart, nervous system and kidneys in adults. Mercury enters the environment via pollution from power plants, chlorine production facilities, waste incinerators and other sources.

The report from Oceana and the Mercury Policy Project provides more comprehensive information than any recent releases by the Food and Drug Administration (FDA), the groups note. It includes analyses of swordfish and tuna samples purchased at such popular supermarket chains as Safeway, Shaw's, Albertsons and Whole Foods in 22 states.

The samples were tested between July 7 and August 11 at the University of North Carolina's Environmental Quality Institute.

Average Exceeded FDA Safety Levels

The findings suggest that a typical shopper buying swordfish in a grocery store has a 50 percent chance of buying a swordfish steak with mercury levels considered unsafe by the FDA.

The average mercury concentration in the 24 swordfish samples -- 1.1 parts per million -- exceeded the amount at which the FDA can take legal action to remove a product from the market, which is 1.0 ppm.

Two samples contained more than 2 ppm; one came from Maine and one from Rhode Island.

The average mercury concentration found in 31 samples of fresh or frozen tuna steaks, 0.33 ppm, is comparable to the mercury level in canned albacore tuna.

In 2004, the FDA and the Environmental Protection Agency (EPA) issued a joint advisory recommending that children and women of childbearing age should limit consumption of canned albacore tuna and fresh tuna to 6 ounces per week and avoid consumption of shark, swordfish, king mackerel and tilefish altogether.

Forty-five states also have issued advisories warning sensitive populations about the dangers of eating mercury-contaminated fish.

Point-of-Sale Warnings Needed

"The results clearly demonstrate the need for signs in our supermarkets to communicate the FDA advice because people are unknowingly purchasing these high-mercury fish, and women of childbearing age and children may be eating them in spite of the FDA’s warning," said Jackie Savitz, director of Oceana’s Seafood Contamination Campaign.

"Americans have a right to know what's in their food, and posting warning signs in grocery stores where these fish are sold is a simple, common-sense solution that fulfills that right," Savitz added.

The groups also called on the FDA to bolster its testing program.

They noted that their project, Fair Warning: Why Grocery Stores Should Tell Parents About Mercury in Fish, analyzed and reported on six times more swordfish than the FDA has evaluated in the past five years, and eight times more tuna steaks than the FDA has examined in the past eight years, according to the FDA's database.

"Pregnant women and parents of young children need point-of-sale warnings to make informed choices about the fish they purchase," said Michael Bender, director of the Mercury Policy Project.

"Based on our test results, a 44-pound child eating six ounces of tuna weekly would be four times over the EPA's reference dose, and a 120-pound woman eating just six ounces of tuna weekly would be eating one and one-half times EPA's reference dose," he pointed out.

The EPA reference dose is an estimate of the amount of methyl mercury that could be consumed without causing an appreciable risk of adverse health effects over a lifetime.

US Opposes California Warning Labels

To protect and inform the public about the risks of mercury poisoning, the coalition offers these recommendations:

The last recommendation was offered in response to FDA Commissioner Lester Crawford's recent opposition to the State of California's efforts to protect families by requiring mercury warning labels on canned tuna in grocery stores.

California Attorney General Bill Lockyer maintains that the FDA does not have the authority to pre-empt the state's law.