More than half of canned tuna samples from a local grocery store failed to meet the strict Environmental Protection Agency safety level for mercury in fish, according to a new study by University of Nevada, Las Vegas researchers.
The study also found that 5 percent of the more than 300 samples exceeded the guideline set for consumers by the Food and Drug Administration.
The team led by UNLV environmental health professor Shawn Gerstenberger recommends stricter and consistent regulation of mercury in canned tuna, which accounts for almost 35 percent of all seafood consumed in the United States. Americans eat about 1 billion pounds of canned tuna per year.
"The variation in data both in the literature and throughout the present study suggest the need for a long-term monitoring program to ensure the safety of tuna that we consume," concludes the study, to be published in the February issue of the journal Environmental Toxicology and Chemistry. The report by Gerstenberger, Adam Martinson and Joanna Kramer appeared for review by other scientists on the journal's Web site in October.
In an interview Monday, Gerstenberger said, "I wouldn't tell people to not eat tuna but choose the right type and space out the meals."
But a spokesman for the National Fisheries Institute said consumers shouldn't be concerned by the UNLV report because the Environmental Protection Agency safety level is not relevant to tuna harvested by commercial ocean fleets.
Instead, the EPA level applies to sport-caught fish from lakes, streams and waterways in the United States and is used as a measure for regulating emissions from power plants and mining operations and other sources of mercury contamination.
In many cases, mercury is released into the atmosphere from burning fossil fuels or disturbing soil. It then rains out over land and bodies of water.
"It is critical to point out that the methylmercury found in seafood like canned tuna is predominantly the result, not of emissions, but of naturally occurring processes found in the ocean like underwater volcanic activity," said Gavin Gibbons, a spokesman for the National Fisheries Institute. The institute includes the Tuna Council, which represents the three major U.S. tuna processors, Bumble Bee, Chicken of the Sea and StarKist.
Nevertheless, Gerstenberger noted that the 1 part-per-million FDA action level for methylmercury and the EPA's more stringent 0.5 part-per-million safety level for mercury in sport-caught fish both pertain to human consumption.
As such, he said, regulatory agencies need a uniform standard for consumption of tuna and other fish that contain methylmercury, which is the metal-organic compound of the element formed in aquatic systems. It binds to protein and accumulates in fish flesh.
Mercury poisoning can damage the central nervous system, cause hearing loss and diminish vision. Its effects are especially pronounced in infants, children and developing fetuses.
For the UNLV study, 300 samples were taken from three brands of canned tuna during a four-month period, from November 2005 to February 2006. The report, for legal reasons, doesn't specify the brands or name the store where the samples were collected.
The study recommends clearly stating the risks of mercury poisoning to consumers. It notes that albacore, white tuna, accumulates more mercury than skipjack, light tuna. Albacore are typically larger fish, weighing between 25 pounds and 45 pounds whereas light tuna is mainly skipjack that weighs between 6 and 12 pounds.
In an e-mail, Food and Drug Administration spokeswoman Rita Chappelle said FDA's action level for methylmercury was developed in the 1970s as a regulatory tool to keep consumers within an acceptable daily intake level. That level is 10 times lower than what triggers adverse health effects from methylmercury in adults.
The primary public health issue, she said, relates to pregnant women consuming fish and the potential effects on nervous system development in fetuses.
"To cover that possibility, FDA and EPA have jointly issued a consumer advisory that recommends that pregnant women eat fish but that they not exceed 12 ounces per week for most species, including light canned tuna," Chappelle said.
The recommendation for albacore, white canned tuna, is 6 ounces per week because albacore on average has more methylmercury in it than light tuna, she said.
Albacore accumulates more mercury through the food chain than skipjack, or light tuna.
Under the EPA guideline, a 55-pound child is allowed to eat 2.6 ounces every 15 days to stay below the established reference dose.
The research team found that one brand of canned tuna had significantly higher levels of mercury than the other two. The same 55-pound child eating the same amount, 2.6 ounces, should go more than 23 days between meals of chunk white tuna to stay within the safe dose range.
Gerstenberger said he hopes the study will "stimulate some discussion about a standard that's more user friendly for the public."
Funding for the study was provided from part of a $5,000 undergraduate research award from UNLV.
Contact reporter Keith Rogers at krogers@ reviewjournal.com or 702-383-0308.