Researchers found mercury levels in Hawaiian yellowfin tuna are on the rise.
Mercury can pose a significant threat to humans who consume large predatory fish that carry it, the University of Michigan reported. The primary source of mercury is atmospheric deposition from human activity such as coal burning and gold mining.
The potent toxin was found to be increasing in the fish at a rate of about 3.8 percent per year from 1998 to 2008. For decades, researchers have been expecting this phenomenon to occur due to rising atmospheric concentrations. This is some of the first evidence that shows these mercury levels are actually rising as was expected.
"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," said Paul Drevnick, an assistant research scientist at the U-M School of Natural Resources and Environment and at the U-M Biological Station. "This study confirms that mercury levels in open ocean fish are responsive to mercury emissions."
To make their findings the researchers looked at data from three studies that sampled the same yellowfin tuna population near Hawaii in 1971, 1998 and 2008. The analysis used a computer model that controls for factors such as the influence of body size; the re-analysis included 229 fish. The researchers found mercury concentrations did not change in the fish between the years of 1971 and 1998, but the period between 1998 and 2008 saw some significant changes.
"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."
The findings were published in a recent edition of the journal Environmental Toxicology and Chemistry.
