Canned tuna - for its convenience, affordability and health benefits - has long been a staple of the American diet and is even subsidized by the federal government as a nutritional supplement for low-income mothers and their children. However, a new UNLV study found that elevated mercury levels in canned tuna may pose a hidden health risk.
In a study published in the February 2010 issue of the journal Environmental Toxicology & Chemistry, UNLV researchers tested more than 300 samples of canned tuna from three top national brands and found more than half contained mercury levels above what the U.S. Environmental Protection Agency (EPA), which regulates recreationally caught fish, considers safe for human consumption.
Fifty-five percent of the samples topped the EPA standard of 0.5 parts per million (ppm); five percent exceeded 1.0 ppm, the safety level set by the U.S. Food and Drug Administration (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.
"Canned tuna accounts for more than a quarter of the nation's seafood consumption and creates some significant regulatory challenges," said Shawn Gerstenberger, UNLV environmental and occupational health professor and lead author on the study. "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."
Researchers tested 155 cans of three national brands collected in Las Vegas grocery stores over a four-month period, segregating tuna 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 recommended EPA limits for safe consumption, 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.
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 different species of fish than "light" variety tuna that is 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 and reduce the source of the exposure," said Gerstenberger.
The study recommends that regulatory agencies require the tuna industry to provide detailed information to consumers regarding the mercury content of each product and disclose the locations at which the tuna are caught. Researchers also urge more consistent consumption guidelines to lessen consumer confusion, citing the disparity between safety levels set by the EPA and FDA. 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.
Media interested in obtaining a copy of the publication can contact Tony Allen at (702) 895-0893 or Tony.Allen@unlv.edu.
