Mercury Rising: A Bad Sign if You Eat Fish

05-16-2013
Mercury Fish

USF research reveals high mercury levels in California fish.

Allison Luengen, assistant professor of environmental science/management at USF, worries that California consumers are being sold fish with high mercury levels at popular grocery stores, fish markets, and sushi restaurants. 

She raised the alarm recently after finding that 11 percent of the fish sampled in her lab exceeded the Food and Drug Administration's (FDA) recommended limit of one milligram of the chemical compound methylmercury (the form that builds up in living organisms) per kilogram of fish-some by more than 1.76 times the FDA limit. Luengen partnered with the California Academy of Sciences and NBC Universal on the project.

Stunts development

Methylmercury can stunt cognitive development, memory, attention, language, and fine motor and visual spatial skills, according to the Environmental Protection Agency. It builds up in the body over time, and its effects vary depending on the amount consumed, body mass, and an individual's sensitivity to the toxin. 

"My goal is to increase awareness," Luengen said, "because the message clearly is not getting out to people."

Mercury can be particularly problematic for "sensitive populations" like expectant mothers and small children. Scientists with the Great Lakes Advisory Workgroup suggest they consume no more than 5 percent of the recommended adult level, or 0.05 mg/kg. "By that measure, 81 percent of the fish measured in this study were too high," Luengen said.

Swordfish, tuna on worst list

The fish testing highest for methylmercury in Luengen's lab were swordfish, bigeye tuna, and albacore tuna, which tested up to 1.76 times the recommended FDA limit. Fish with the least mercury were Atlantic haddock, Atlantic salmon, and Pacific cod, said Morgan Cambell '13, an environmental science major who worked with Luengen on the project.

"It might be easy for shoppers to recognize and avoid swordfish, but distinguishing the medium- from the low-mercury seafood is where things get complicated," Luengen said. "If you eat fish regularly, this difference could be important."

Consumers who avoid swordfish and other species with high mercury levels might still be at risk, because up to one-third of the fish sold across the country is mislabeled, according to separate studies by NBC Universal and conservation group Oceana. Several species of fish tested by Luengen were also mislabeled, including three samples of Pacific Ocean perch-a species that has one of the lowest mercury contents on average.

by Ed Carpenter »email usfnews@usfca.edu | Twitter @usfcanews