Is there something fishy going on with that can of tuna you had for lunch?

A new UNLV study has found that canned tuna - a staple of the American diet - contains elevated mercury levels that may make the food a health risk. Researchers also are urging stricter oversight of the product.

"Canned tuna accounts for more than a quarter of the nation's seafood consumption and creates some significant regulatory challenges," said Shawn Gerstenberger, environmental and occupational health professor and lead author on the study.

The study, which was published by the journal Environmental Toxicology and Chemistry, recommends that regulatory agencies require the tuna industry to provide detailed information to consumers regarding the mercury content and disclose the locations at which the tuna are caught.

Researchers also urge more consistent monitoring guidelines to stem consumer confusion, citing the disparity between safety levels set by the U.S. Environmental Protection Agency (EPA) and the U.S. Food and Drug Administration (FDA).

They tested more than 300 samples of canned tuna from three top national brands and found:

• 55 percent topped the EPA standard for mercury of .5 parts per million (ppm). The EPA regulates recreationally caught fish.
• 5 percent exceeded 1.0 ppm, the safety level set by the FDA for commercially sold fish.

Health effects from mercury poisoning include central nervous system damage, hearing loss, and diminished vision, and are especially pronounced in developing fetuses, infants, and children. According to EPA guidelines, which many states have adopted, an average child could only consume one can of tuna every 18 days to maintain acceptable level of mercury exposure.

"With pregnant women and children the most susceptible to mercury poisoning - yet also among the top consumers of canned tuna - federal agencies need to urge distributors to expressly state mercury levels contained in their products," Gerstenberger said.

Putting Tuna to the Test

Researchers collected tuna from multiple Las Vegas grocery stores over a four-month period and segregated them by:

• Brand
• Type (white vs. light)
• Packaging medium (oil vs. water)
• Lot number and expiration date

All brands tested contained samples with mercury levels higher than the EPA recommendations, and two of three had concentrations higher than FDA standards. The study revealed significant differences in mercury concentration by brand and type, with one brand showing consistently elevated mercury levels.

Mercury Rising

For the second phase of the study, 147 cans of the brand with the highest mercury levels were tested again to confirm the initial results. While no significant difference was found by packaging medium or expiration date, 53 percent of all cans contained mercury levels greater than .5 ppm, with white tuna across brands registering the highest concentrations. White tuna comes from albacore, a fish that resides closer to the water's surface than "light" variety tuna, and is therefore more susceptible to mercury pollution from human sources.

"Mercury concentration in fish has a lot to do with the environment they're in, but since the locations of where the fish are harvested are not made available to consumers, it is very difficult to positively identify the source of the exposure," said Gerstenberger.