ANN ARBOR, Mich., Feb. 3 (UPI) — Mercury levels are up in the Earth’s atmosphere, and researchers at the University of Michigan say the evidence is likely already evident in tuna rolls at sushi restaurants across the country.
As part of a recent survey, a team of international researchers led by scientists at Michigan looked at several decades of data on mercury levels measured in Pacific tuna caught off the coasts of Hawaii. After controlling for the varying ages, weights and body sizes of the sampled tuna (using advanced mathematic models), researchers showed the concentration of mercury among yellowfin have been rising at a clip of 3.8 percent per year since the 1970s.
“The take-home message is that mercury in tuna appears to be increasing in lockstep with data and model predictions for mercury concentrations in water in the North Pacific,” study author Paul Drevnick, an assistant research scientist at Michigan’s School of Natural Resources and Environment, explained in a recent press release. “This study confirms that mercury levels in open ocean fish are responsive to mercury emissions.”
Trace levels of the heavy metal mercury end up in the atmosphere as a result of human activities. Eventually the metal leaches into the ocean and into the marine food chains. Because large fish like tuna and swordfish are prolific predators with relatively long lives, the toxic metal has time to accumulate as it travels up the food chain — from plankton to small fish, small fish to medium fish, medium fish to big fish.
Researchers say much of the mercury that ends up in the Pacific comes from the industrial activities in China, specifically coal plants.
None of the levels of mercury, now or in previous decades, were high enough to be of immediate danger to consumers, scientists say. Even the highest concentrations were less than one part per million. Doctors, dietitians and food safety experts continue to stress that the heart-healthy benefits of a fish-heavy diet far outweigh any dangers of trace amounts of mercury. Still, researchers do warn against children and pregnant women eating too much high-mercury fish.
But the main takeaway from the new study, researchers say, is that human impacts on the atmosphere have almost immediate consequences on wildlife, including the kinds of wildlife we continue to put on the dinner table.
The study was published this week in the journal Environmental Toxicology and Chemistry.
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