TORONTO – The current health benchmarks for mercury levels in fish are outdated and inadequate and should be strengthened worldwide, according to two international reports released on Tuesday.
Researchers at the Biodiversity Research Institute (BRI), a non-profit ecological research group, have released a new report that looks at the worldwide extent of mercury contamination in fish and other marine life, based on thousands of scientific reports collected from around the globe.
The report found that mercury contamination of fish and other marine life is global in scope.
“Mercury contamination is ubiquitous in global marine ecosystems and is more severe than realized,” said Dr. David Evers, executive director and chief of BRI in a global web conference with journalists on Tuesday.
The second report, released by the Zero Mercury Working Group-an international coalition of environmental campaign groups-found that various marine organisms regularly harvested and consumed by people have mercury concentrations that exceed safety levels that were considered “safe” just years ago.
The reports paint the first comprehensive, global picture of mercury levels in seafood.
In January 2013, the fifth and final round of United Nations negotiations for a global mercury treaty is expected to take place in Geneva. The Governing Council of the United Nations Environment Programme (UNEP) is taking action to develop a global, legally binding treaty designed to monitor and regulate mercury emissions.
Mercury in marine life
Globally, mercury concentrations are highest in large, long-lived pelagic species-like the marlin, Pacific bluefin tuna, the wide-ranging swordfish and the king mackerel-and commonly exceed safe levels, according to the BRI report.
Conversely, many commonly harvested species like shrimp, cod, haddock, herring, and sardines have low body burdens of mercury.
According to data from the United Nations Food and Agriculture Organizaiton (FAO), nearly 40 per cent of the global fish production enters international markets for either direct consumption or food processing. Tuna is consistently among the top five commodities in the global fish market. Yellowfin, skipjack, and albacore are the most common species utilized by the tuna canning industry, while bluefin tuna is highly sought after for direct consumption.
For years, experts argued that mercury is a pollutant of global importance that adversely impacts ecological and human health. The consumption of marine shellfish, fish, and marine mammals represents one of the primary pathways through which humans are exposed to mercury.
The need for current and adequate guidelines
According to experts and research, mercury and its compounds are highly toxic to humans, especially to the developing nervous system.
Methylmercury is the organic form of mercury that most easily builds up in organisms like marine life and can persist for long periods of time. According to the U.S. Environmental Protection Agency, exposure in the womb to methylmercury can impair neurological development. Experts claim this can result from a mother’s consumption of fish and shellfish that contain methylmercury, which can adversely affect a baby’s growing brain and nervous system.
For years, health experts advised the public to limit their consumption of marine life with high levels of mercury. Cod, salmon and flounder are considered “low mercury” fish, particularly when compared to marlin, tuna, mackerel, swordfish and grouper, which, according to the latest reports, all manifest high levels of mercury contamination.
The EU advises pregnant or breastfeeding women not to eat tuna more than twice a week, while Health Canada advises women who are or who may become pregnant or who are breastfeeding eat only up to four Food Guide Servings of canned albacore tuna each week.
The U.S. Environmental Protection Agency recommends people “should eat mainly types of fish low in mercury and limit your consumption of types of fish with typically higher levels of mercury.”
“The current safety levels are based on science from a decade ago,” said Dr. Edward Groth an adviser to the World Health Organization and the Food and Agriculture Organization on such issues as methylmercury in fish. “The reference dose is supposed to provide a margin of safety and it doesn’t.”
Health effects from mercury consumption
In 2006, a study from Poland tested one-year-olds for cognitive and psychomotor development and found substantially delayed development in children with higher prenatal mercury exposure.
A 2008 study that looked at the relation between cord blood mercury levels and early childhood development found that fish eaten during pregnancy had substantial beneficial effects on cognitive development in children tested at 12, 24, 36 and 48 months of age, while elevated prenatal methylmercury exposure significantly adversely affected the same functions-psychomotor development, verbal and full IQ.
Researchers of both reports say that the health effects of fish consumption and research studying them are complicated by the fact that fish contains beneficial nutrients and that fish consumption during pregnancy and by young children is essential for brain development.
In fact, some studies have associated improved cognitive performance with elevated methylmercury levels, suggesting that the beneficial effects of fish nutrients were greater than the adverse effects of mercury in those cases.
“In research, beneficial effects of nutrients can hide the negative effects of mercury, and vice versa,” read one report. “In risk management, women and children should not avoid fish or eat less fish-which could harm their health. Instead, they need guidance to choose low-mercury fish and shellfish.”
Dr. Philippe Grandjean, professor and chair of environmental medicine at the University of Southern Denmark and an adviser to the Danish National Board of Health, said food agencies around the world have the responsibility to point consumers in the right direction instead of warning them about the wrong direction.
“We are taking developing brains hostage and we are allowing the pollutant to interfere with a very precious organ, ” said Grandjean in the web conference on Tuesday.
According to the BRI report, about two thirds of the fish and shellfish on the market worldwide are very low in mercury and are safe to eat.
Mercury pollution
A 2012 study on mercury biogeochemical cycling in the ocean and policy implications found that concentrations of mercury in the global environment have increased approximately threefold as a result of anthropogenic activities, and the world’s oceans are one of the primary reservoirs where mercury is deposited.
According to 2009 data that looked at mercury sources and distribution in the North Pacific Ocean, present atmospheric mercury deposition rates will result in mercury concentrations doubling in the Pacific Ocean by 2050.
“Measures must be taken immediately to reduce mercury pollution in the global environment, which will eventually reduce concentrations in fish,” said one report.
Even with strong actions by governments, it will take some time for mercury pollution to be reduced in the global environment said Groth.
“Mercury emissions do not seem to be reduced anytime soon,” said Groth. “The system is broken and we cannot let it continue.”
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