Seafood mercury more harmful than believed
A report to be released Tuesday by the Biodiversity Research Institute in Gorham, Maine, evaluates t…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.
“There are adverse effects” for average consumption, said environmental health scientist and consultant Edward Groth of Pelham, N.Y., who authored the epidemiological study included in the Biodiversity Research Institute report.
“You can’t get mercury out of fish; you have to teach people” which species are relatively safer than others, Groth said. “Some people will stop eating fish and that would be a bad idea (because) fish is wonderful nutritionally.”
What is needed, Groth said, is a more current and clearer understanding of “acceptable intake” of mercury. The target exposure set by the U.S. Environmental Protection Agency in 1999 is not adequate, he said, and needs to reflect a broader knowledge base and greater epidemiological understanding.
“As we learn more about human exposure to chemicals … (it) is not uncommon for guidelines to be lowered,” said Amanda Sears, associate director of the Environmental Health Strategy Center in Portland. Acceptable lead levels, for example, have been lowered several times over the past century as more became known about its potential harm.
The institute findings might also provide valuable information to populations in which there are greater “pockets of exposure,” she said.
“Mercury is a potent neurotoxin that can affect the way that children think, talk and walk,” said Emily Figdor, executive director of Environment Maine in Portland. “The good news is that the Obama administration has finalized strong new rules – which were more than 20 years in the making – to crack down on mercury emissions from power plants, the largest U.S. industrial source of the pollution. But much more can be done to move away from dirty energy sources that emit mercury and other harmful pollutants and transition to clean, renewable energy.”
Sources of mercury contamination in Maine include older landfills, Evers said, along with airborne contamination, primarily from out-of-state coal-fired power plants. Waste incineration plants, pesticides and other chemical compounds, along with some everyday household and medical products, also have been cited as sources.
The institute has been studying mercury levels for more than 15 years. It assesses emerging threats to wildlife and ecosystems and uses its findings to raise awareness and inform decisionmakers.
The U.N. meetings in January in Geneva will be the fifth, and potentially, final discussions prior to a legally binding agreement for participating nations.