A new study conducted by researchers from the University of Michigan has revealed that the concentration of mercury in the Hawaiian yellowfin tuna is rising at a rate of at least 3.8 percent annually. This could be attributed to an increase in the atmospheric levels of mercury.
For the study, the researchers re-examined the data from earlier research, which analyzed the mercury levels in the muscle tissues of yellowfin tuna caught near Hawaii. They found that while there was no detectable increase in mercury concentration between 1971 and 1998, the concentration of mercury in fish has risen by at least 3.8 percent per year from 1998 to 2008.
The findings, published in the journal Environmental Toxicology and Chemistry on Feb.2, provide additional evidence that air pollution from the burning of coal pumps mercury into the food chain in the ocean, posing potential hazards to human health.
Mercury is toxic and it is known to affect the development and function of the nervous system, particularly the brain. It is also being held responsible for developmental problems and lower IQs in exposed children.
The toxic substance can accumulate in high concentration in fish, particularly predatory marine fishes such as tuna and swordfish.
David Krabbenhoft from the U.S. Geological Survey said that mercury travels up the food chain, so higher concentrations of the toxic trace metal can be found in higher quantities in larger and older creatures, particularly predatory species. This is why it is preferable to consume small fish, such as sardines or those that primarily feed on plankton.
Besides emissions from coal power plants, mercury in the open ocean can also be traced back to artisanal gold mining.
"Evidence is piling up that the methyl mercury has an anthropogenic source," said study researcher and eco-toxicologist Paul Drevnick from the University of Michigan. "It's coming from mercury emissions that are falling into the ocean."
Study co-researcher Carl Lamborg said that the levels of mercury present in the yellowfin, which is not at the top of the food chain, is concerning because it indicates that the amount of mercury in fish is increasing all the time. If mercury levels keep rising, most kinds of fish could potentially become hazardous at some point.
"Mercury levels are increasing globally in ocean water, and our study is the first to show a consequent increase in mercury in an open-water fish," Drevick said. "More stringent policies are needed to reduce releases of mercury into the atmosphere. If current deposition rates are maintained, North Pacific waters will double in mercury by 2050."
Though mercury levels are rising, there's no need to ditch the sushi just yet, because the health benefits of eating the fish still continue to outweigh the risks of consumption of mercury, which is still far from reaching dangerous levels.
"The demonstrable and scientific health benefits of eating seafood continue to far outweigh the theoretical risks," National Fisheries Institute said in an emailed statement to Tech Times. "This study is neither about human health nor nutrition, and does not illustrate any harm from eating tuna or any other seafood. It should not be used to offer nutrition advice to readers, listeners or viewers. Regardless of minute increases suggested in this report, mercury levels in tuna remain far below any levels associated with harm."
"More than a decade's worth of published, peer-reviewed science clearly demonstrates eating fish leads to concrete health benefits including, but not limited to, improvement in cardiac health, boosts fetal and infant cognitive development, and higher intelligence. To suggest this study in any way undermines the current science and these proven facts, or should be taken into account when consuming fish, is disingenuous and misleading," it said.