The industry's association yesterday disputed a three-part series of reports by the Chicago Tribune, which claimed that tests conducted on the paper's behalf by Rutgers University showed dangerous levels of mercury in canned tuna.
The Tuna Foundation turns the study on its head, claiming that the Rutgers tests in fact confirm that mercury levels in the canned version of the fish are below the " very conservative limit" set by the Food and Drug Administration (FDA).
The dispute continues the long running battle between consumer groups, scientists, the FDA and industry, all of whom cite various studies as supporting either a position that high levels of mercury are turning up in canned tuna, or that the traces found are not harmful to health at all.
The claims and counter-claims over the scientific evidence could lead to confusion in the marketplace, and perhaps a reversal in the stable demand in the US for tuna.
Titled "The Mercury Menace", the Chicago newspaper's series claims that government and industry are failing to protect consumers by ignoring the incidents of high levels the newspaper found in locally sold canned tuna. The tests indicate that supermarkets are selling canned tuna that regularly exceed the mercury levels set by the FDA.
The Tuna Foundations says that compared to ongoing FDA tests, which find that canned light tuna has an average of 0.12 parts per million (ppm) of mercury and canned albacore tuna has an average of 0.35 ppm, the Rutgers tests puts the average amount of mercury in light canned tuna in Chicago area supermarkets at 0.11 ppm and albacore tuna at 0.30 ppm.
"These findings should have been reported as good news for consumers because the mercury levels are very low and fall within the limits set by FDA," stated David Burney, the association's executive director. "But unfortunately, the findings were used to raise concerns about eating tuna when the real risk to the public is not getting enough canned tuna and other fish in the American diet."
He cited the findings by Harvard Center for Risk Analysis, which claimed that the health benefits of consuming seafood far outweigh any risk due to trace amounts of mercury in fish.
The Harvard Center study concludes that for women of childbearing age, benefits can be achieved with virtually no negative impact on the developing child if women of childbearing age eat two servings a week of fish that are low in mercury.
The study was published in the November 2005 issue of the American Journal of Preventive Medicine. The Harvard researchers contend that if Americans reduce their fish consumption out of confusion about mercury, there will be serious public health consequences, notably higher death rates from heart disease and stroke.
"From the standpoint of public health, the real risk for the public is not getting enough canned tuna in your diet," said Burney "If the public reduces or eliminates fish consumption based on unsubstantiated risks concerns, they will lose a number of well-established health benefits."
The association also disputed the newspaper's claim that 460,000 children may be at risk from mercury levels in fish. No one in the US has been shown to have anywhere near the amount of mercury in their system from eating seafood known to cause a health problem, it claimed.
This is supported by two large studies conducted by the Centers for Disease Control and Prevention (CDC), which found all of the women and children studied were significantly below any known adverse effect level.
The association also challenged the Chicago Tribune's reports about the use of yellow fin tuna in canned light tuna. According to the Rutgers findings, the amount of mercury in the Yellow Fin analyzed is 0.06 parts per million -- lower than regular canned light.
"Moreover, the Chicago Tribune confuses the higher levels of mercury in yellow fin steaks, which are eaten infrequently, with what is used in canned light tuna," the association stated.
The industry is under pressure in California, where the state attorney general, Bill Lockyer took five grocery stores to court in a bid to get them to post warning labels on fish that may have levels of mercury in them. The lawsuit was filed under Proposition 65, the voter initiative that requires businesses to alert the public they are being exposed to dangerous chemicals.
Californian tuna canners also joined the lawsuit.
All types of fish contain some amounts of mercury. For most people this is not a cause for concern, but a build-up in the blood stream can lead to reproductive problems in women and affect the development of the nervous system in children.
The FDA therefore advises that people eat up to 12 ounces (two average meals) a week of fish and shellfish that are lower in mercury, such as canned light tuna, salmon, pollock, and catfish.
As albacore tuna and fresh tuna steaks contain more mercury than light tuna, the agency says that consumption of this variety should be limited to 6 ounces per week.