Study: Seafood mercury more harmful than believed


SeafoodSource staff

Published on
December 3, 2012

A report to be released Tuesday by the Biodiversity Research Institute in Gorham, Maine, evaluates the amount of mercury in fish species around the world and suggests that levels of the toxin previously deemed safe are probably not.

The report, “Mercury in the Global Environment,” is part of evidence being compiled for talks next year on a proposed United Nations global treaty to reduce mercury use and pollution, said David Evers, executive director of the institute and part of the U.N. Environment Programme Fate and Transport Partnership Group, which is evaluating the worldwide data.

The report is the first to track data globally on fish species.

The institute’s data show two things: That mercury contamination of seafood is global in scope, and that negative health effects from methylmercury in seafood are occurring at levels below what was considered safe just a few years ago.

“The more we look at mercury, the more toxic it is,” said Evers. “Threats from mercury are greater at lower levels than we have thought in the past.”

The institute’s report brings together evidence and documentation from studies of fish all over the world, said Evers. It shows that fish species from the Gulf of Maine are about “average” for mercury contamination, but not as toxic as some other large predatory species, he said.

Cod, salmon and flounder are considered “low mercury” fish, especially when compared to marlin, tuna, mackerel, swordfish and grouper, which all manifest high levels of mercury contamination, Evers said.

Some of these high-mercury varieties aren’t found in the Gulf of Maine, but that doesn’t mean state consumers can ignore the threat.

“The bad news is that there’s a problem with mercury, and it’s ubiquitous,” said Deborah McKew, the institute’s communications director. “You have to be careful what you eat.”

Mercury “affects the immune system, alters genetic and enzyme systems, and damages the nervous system, including coordination and the senses of touch, taste and sight,” according to the U.S. Geological Survey’s fact sheet on the neurotoxin. “Methylmercury is particularly damaging to developing embryos, which are five to ten times more sensitive than adults.”

Methylmercury is the organic form of mercury that most easily builds up in organisms and persists for long periods of time. Mercury enters the environment from many sources, from coal-burning plant emissions to dental fillings. It is also “bioaccumulative,” which means it is stored in fatty tissue and builds up until it reaches toxic levels.

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