Methyl mercury is the organic form mercury takes in fish, usually large fish that reside higher up in the aquatic food chain. Mercury pollution comes from several sources, including the burning of fossil fuels in coal-fired electric power plants, disposal of mercury-containing products in incinerators and landfills, and industrial processes such as chlorine production.
The Centers for Disease Control and Prevention in Atlanta cites mercury as a potent toxin that can be harmful to fetuses, infants and young children. The CDC estimates one in 12 women of childbearing age has unsafe mercury levels in her blood, which could place 300,000 babies at risk for mercury poisoning every year. Swordfish and shark, popular entrees in restaurants, also are high in mercury, although they are not as widely consumed as tuna.
Canned tuna -- the "chicken of the sea" -- is the most common fish consumed in the United States, accounting for 25 to 35 percent of the total and eaten in 90 percent of American homes. Children eat more than twice as much tuna as any other fish and canned tuna is one of the nation's major sources of protein.
"That is the fish most Americans eat," Linda Greer, director of the National Resources Defense Council's environment and health program, told United Press International. "It's quite a pervasive problem."
White albacore canned tuna alone accounts for roughly one-third of all canned tuna sold in grocery stores coast to coast. So the Mercury Policy Project, a public interest organization in Montpelier, Vt., decided to study mercury levels in canned tuna on store shelves.
They took cans of Starkist, Bumblebee, and Chicken of the Sea from Safeway, Whole Foods, Trader Joe's, Shaw's and other stores and sent the cans of both white albacore and light tuna to labs in Michigan and California. Their findings, released earlier this month, revealed mercury levels were more than 30 percent higher than either the tuna industry or the U.S. government had reported.
Based on MPP's calculations, one out of every 20 cans of white albacore tuna should be recalled as unsafe for human consumption. Of the 48 tuna samples, over three were found to contain mercury levels higher than the Food and Drug Administration's one-part-per-million safety threshold. On average, the white albacore tuna had mercury levels four times higher than the 12 cans of light tuna tested.
"If a 22-pound toddler ate only two ounces of white tuna with that level of mercury, they would exceed the Environmental Protection Agency's virtual safe dose, called the reference dose, by four times," Michael Bender, MPP's director, told UPI. If a 132-pound woman ate two cans of tuna per week, she would exceed the EPA's limit by four times, he added.
The issue of mercury in fish is not just an American problem -- it is a global problem.
On June 26, the Joint Food and Agriculture Organization of the United Nations and the World Health Organization Expert Committee on Food Additives issued recommendations calling for the WHO to lower its safe level by half. The NRDC, an environmental watchdog group in Washington, D.C. said the joint committee's recommendations are twice as stringent as the FDA's. The NRDC claims the FDA is relying on obsolete data.
"The seat of the blame right now is really on the FDA because they are in charge of our food supply," Greer said. "We are so far behind the ball with the FDA. They're really asleep at the switch. They're shying away from declaring a problem that they would need to solve."
Deborah Rice, a toxicologist who left a senior science post at the Environmental Protection Agency a few months ago to join the Maine Department of Environmental Protection in Augusta, Maine, said the FDA might be influenced by the fishing industry.
"There's no question the commercial fishing industry -- no doubt the tuna fishing association -- has ready access to the FDA," Rice told UPI. "The FDA, at this point, is out of step, not only with the EPA, but also with the European Union and the United Kingdom." Rice said there is no way the FDA could be providing scientifically useful guidance to consumers because "the FDA is not monitoring, so it doesn't really know the levels of mercury in the fish."
An FDA consumer advisory issued in 2001 states that individuals, including pregnant women, can safely consume up to 12 ounces of cooked fish per week. The typical can of tuna is six ounces. The advisory also states there is no harm in eating more than 12 ounces per week "as long as you don't do it on a regular basis."
"How crazy it is that we need to be telling, particularly pregnant women, how much fish we eat, and that's our policy?" Greer asked. She added the NRDC has filed a Freedom of Information Act request to get the FDA to release its data on tuna and mercury. Greer also said the NRDC is considering taking legal action against the agency.
An FDA spokeswoman told UPI: "We have a consumer advisory and that advisory is targeted for a certain segment of the population, which is mainly pregnant women and women of childbearing age. As of now, we are standing by our consumer advisory on methyl mercury in fish. Based upon comments we've received from the food advisory committee, (the FDA is) looking into addressing the tuna issue further."
The FDA would not specify how it will examine the issue further, nor did the agency supply any answers regarding its tuna testing program. Bender said the FDA's testing program ended in 1998. The commercial fishing industry does its own mercury testing, but the MPP and the NRDC claim the companies have not been forthcoming with the data.
Some states are not waiting for the FDA to act. Eleven have issued advisories -- including states bordering the Great Lakes region where mercury in fish has been a problem -- warning pregnant women and children to limit their consumption of canned tuna.
Randi Thomas, a spokeswoman for the U.S. Tuna Foundation in Washington, said companies have been conducting their own mercury tests since the 1970s. "There's been no change," in the mercury levels, she told UPI. "If anything, there's been a decrease in (the mercury content of) light tuna."
The health warnings coming from the MPP and the NRDC are "absolutely exaggerated," Thomas continued. "To judge the universe by 48 cans (of tuna) is ridiculous," she said, referring to the MPP's Vermont study. "They need to start thinking of the fact they're scaring people away needlessly from an important protein."
The FDA advisory is sufficient, Thomas argued. "We rely on the FDA and the advisory they have (issued) for pregnant women and women of childbearing age and children. This is a very small part of the population that you're talking about and there have been no shown effects," from tuna consumption.
Dr. Jonathan Rutchik, a board-certified physician in both neurology and occupation and environmental medicine and a private practicing neurologist in San Francisco, echoed the Tuna Foundation's assertion there are no clinical data to eating tuna has harmed anyone. He said although the mercury load in tuna remains a concern for the neurological development of the unborn and small children, the health risks for the general population "are probably exaggerated," he told UPI.
In fact, little data exist on the neurological consequences of mercury poisoning from fish consumption in the United States, Rutchik explained. "I have not seen ever, or I don't know anyone who has seen, a patient with a tremor that's related to mercury or from consumption of fish." Although individuals have varying susceptibilities to mercury, most people can "tolerate a little mercury in their blood," he said. "We're not talking about all of a sudden the child becomes retarded."
Another San Francisco physician has come to very different conclusions, however. Dr. Jane Hightower, an internal medicine physician at California Pacific Medical Center, said she initiated a study of her own after seeing patients complain of symptoms, such as difficulty concentrating and thinking, memory loss, muscle and joint pain and even hair loss.
Hightower tested 89 patients -- all but one living in the San Francisco area -- for blood mercury levels. Seven of the patients also provided hair samples. She found 89 percent had mercury levels higher than the safety limits. The study participants, Hightower explained, had consumed a variety of 30 different fish, so their diets were not tuna exclusively.
Still, Hightower found the average mercury level in the women was 10 times higher than recent CDC data covering a nationwide sample. She also discovered 67 patients showed a decline in their blood mercury levels when they stopped eating fish, with the most significant drop occurring in the first three weeks after ceasing fish consumption. After that, the decline tapered off.
"I was surprised we were getting this high a mercury level, I really was," Hightower told UPI. "I was not expecting this."
Her study was published in the April 2003 issue of Environmental Health Perspectives.
Hightower said some of the evidence suggests mercury in the blood increases the risk of cardiovascular problems. "Even if you have a slight elevation of mercury, it can negate the health effects of omega 3 fatty acids," which are found in fish and are known to reduce heart disease risk, she explained.
There are approximately 87 micrograms of mercury in one can of tuna, Hightower said, and the safe limit is only 42 micrograms per week. "Essentially, you shouldn't have more than half a can of tuna per week," she noted. Such mercury levels can double a person's heart attack risk. "With cardiac disease being a leading killer among Americans, it's something to consider," she added.
Another study on tuna and mercury appeared in the May 16 issue of the British journal The Lancet. The research was headed by Dr. Gary Myers, a professor of neurology and pediatrics and the University of Rochester, N.Y.
This study, an update on the Seychelles study, named after the islands in the Indian Ocean, looked at 643 children living there from before birth to age 9 who had been repeatedly exposed to ocean seafood consumption whether through their mothers or on their own. The children were born to mothers who ate an average of 12 meals of ocean fish per week -- about 10 times greater than the average American. Results showed no detectable risk from low levels of mercury. The children, born in 1989 and 1990, have been evaluated five times over the years since their birth.
"The only cases of poisoning of methyl mercury from the consumption of fish that have ever been reported are from Japan and they're from 1960s," Dr. Myers told UPI. The Seychelles study is "one of the largest epidemiological studies to look at this issue. We have not been able to find adverse effects."
Hightower said there is overwhelming evidence to counter the Seychelles study findings. "The Seychelles was one study," she said. "One study does not negate all the other studies."
Rice said every parent needs to be aware of the mercury issue. "The problem is real," she said. "The consumer, particularly (a parent), needs to be educated. Tuna fish is not something that should be consumed by children at will. This is not a theoretical issue -- it's real."