White typically has greater levels of the toxin than light, researchers say
THURSDAY, Feb. 4 (HealthDay News) -- Tests on more than 300 samples of canned tuna from the top three brands in the United States revealed that more than half contained mercury levels above what's considered safe by the Environmental Protection Agency.
Researchers from the University of Nevada, Las Vegas (UNLV), found that 55 percent of the samples had mercury levels higher than the EPA standard of 0.5 parts per million (ppm) and 5 percent had levels higher than the 1.0 ppm safety level set by the U.S. Food and Drug Administration for commercially sold fish.
The health effects of mercury poisoning include central nervous system damage, hearing loss and vision problems.
"Canned tuna accounts for up to a quarter of the nation's seafood consumption and creates some significant regulatory challenges," study author Shawn Gerstenberger, an environmental and occupational health professor, said in a UNLV news release. "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 in their products."
The researchers found significant differences in mercury concentration by type (white and light) and brand. One brand had consistently elevated mercury levels, and white tuna from all three brands had the highest concentrations of mercury. White tuna comes from albacore, a different species of fish than "light" tuna.
"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," Gerstenberger said.
The researchers said federal regulators should require canned tuna producers to provide detailed information to consumers about the mercury content of each product and to disclose tuna harvest locations. In addition, the EPA and FDA need to have similar tuna consumption guidelines to lessen consumer confusion.
The study is published in the February issue of Environmental Toxicology & Chemistry.
Many states have adopted EPA guidelines on tuna consumption, which suggest an average child consume only one can of tuna roughly every two weeks to ensure an acceptable level of mercury exposure.
The U.S. Agency for Toxic Substances and Disease Registry has more about the health effects of mercury.
-- Robert Preidt
SOURCE: University of Nevada, Las Vegas, news release, Jan. 31, 2010
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