Health Canada Reviewing Fish Consumption Guidelines Because Of Mercury Fears

Health Canada Reviewing Fish Consumption
Guidelines Because Of Mercury Fears

By Dennis Bueckert
11-20-4

OTTAWA (CP) - Mounting evidence that mercury contamination can damage fetal brain development has pushed Health Canada to review its guidelines on fish consumption by women of childbearing age, The Canadian Press has learned.

The review comes amid mounting international concern about mercury, with U.S. authorities adopting guidelines for fish consumption that are far stricter than their Canadian counterparts.

Mercury is a toxin spewed by coal-burning power plants, and released by some consumer products. It accumulates in living things and becomes concentrated at higher levels of the food chain, especially in larger fish.

Studies over the last decade suggest that even low levels of mercury in a mother's blood or breast milk can affect the developing brain of her child, leading to learning disabilities and lower intelligence.

Earlier this year, the U.S. Food and Drug Administration issued a directive warning women of childbearing age to eat no more than two meals or 12 ounces of seafood, including canned tuna, weekly.

That directive was based in part on the work of a U.S. Environmental Protection Agency biochemist, Kathryn Mahaffey, who estimates that one in six pregnant women in the United States had high enough blood mercury to damage her child, for a total of 630,000 U.S. newborns at risk.

"We have groups in the United States, in some of our urban areas, whose exposure is every bit as high as in the Inuit populations" in Canada's north, said Mahaffey. "Even though the Inuit eat a lot of fish, so do some of our urban consumers."

Adults are also at risk because mercury can cause high blood pressure, she adds.

Ironically, the urban dwellers with high mercury levels are often health-conscious people who are seeking the dietary advantages of fish, especially heart-friendly omega-3 fatty acids.

Unlike the United States, Canada does not conduct systematic testing for blood mercury in the general population, so similar problems here would not be detected.

Health Canada has no general warning on seafood consumption, although it tells women to limit consumption of several high-mercury species: shark, swordfish and fresh or frozen tuna.

"We are currently in the process of collecting and reviewing data on mercury levels in different fish species, and that review might result in some changes to the guidance," Health Canada expert John Salminen said in an interview.

He said the review will look at all available evidence, including disturbing research among Inuit in northern Quebec's Inuvik region that shows fetuses are being affected by mercury exposure through their mothers' blood.

Canada's Inuit have high blood-mercury levels, mainly because of their high fish consumption, although hydroelectric development may also be a factor. Mercury naturally present in rocks is released in a more dangerous form by microbial processes when vegetation is flooded.

Child-development expert Gina Muckle of Laval University examined 110 Inuit babies from 1996 to 2001 and found evidence of subtle neurological damage that was correlated to levels of mercury in the blood.

"The results are significant in the sense that when I say I see the effect of mercury I have only a five per cent chance of being wrong, which is very scientifically acceptable," said Muckle.

The study involved placing a baby's toy in one of two containers, then distracting him or her for a few seconds. The babies with higher blood mercury more readily forgot the hiding place.

Muckle does not know yet whether these effects will lead to learning problems when the children reach school age, but the U.S. National Institutes of Health has given her group a grant of more than $3 million US to examine that issue.

Research in other parts of the world suggests that mercury contamination can have effects similar to lead poisoning, effectively resulting in a loss of intelligence.

Philippe Grandjean of the Harvard School of Public Health found extensive evidence of learning disabilities among school-age children in the Faroe Islands in the North Atlantic, where mercury-tainted whale meat is a dietary staple.

Grandjean measured the mercury in the hair and blood of hundreds of children, measured their heart beats, tested their cognitive abilities and studied the electrical activity of their brains.

The higher the children's blood mercury levels, the poorer their language skills, attention span and information-processing. Those with higher contamination also had higher blood pressure.

Grandjean's research was a factor in the 2001 decision to lower the U.S. guideline for mercury in maternal blood, said David Acheson, director of food safety and security at the U.S. Food and Drug Administration.

"The previous advice was developed in the mid-'90s and the Science changed," said Acheson. "That earlier advice was not taking into account the newer information from the Faroe Islands . . . in terms of the impact of mercury on childhood development."

The U.S. Environmental Protection Agency now says mercury in maternal blood should not exceed 5.8 micrograms per litre. That is more than three times stricter than Health Canada's limit of 20 micrograms of mercury per litre.

Applying U.S. standards to Inuvik women leads to some alarming conclusions.

Under the Canadian guideline, 16 per cent of Inuvik women of childbearing age have unsafe levels of mercury. Under the U.S. guideline, 79 per cent have unsafe levels.

"The Canadian exposure limit is much too high," says Grandjean. "I even think the U.S. EPA limit is too high. We can see clear effects on brain function below the EPA limit, which means there are effects on brain development."

Grandjean says regulators have been slow to move on the mercury issue because they "hesitate to impact on a very substantial part of the American economy, namely the fishing industry."

In Canada, fishermen defend their product and point out that heavy-metal pollution, including mercury, is a global problem they can't do much about.

"I'm eating fish," says Pierre Verreault of the Canadian Council of Professional Fish Harvesters. "I don't think it's worse than chicken. But we're all concerned about pollution."

Experts say the mercury problem can't be addressed without international co-operation. Most of the mercury in Canada comes from other countries including the United States, Russia, China and India.

So far mercury has not triggered the public concern that led to the Montreal Protocol on protecting the ozone layer and the Kyoto protocol on climate change. But that may change as new research findings become more publicly known.

"Canada seriously lags the European Union and United States in mercury-reduction policy," says Ken Ogilvie, executive director of Toronto-based Pollution Probe.

"I don't think that Health Canada treats it with the sort of priority that we would like to see it treated with. Strangely enough, when I talk to Health Canada they say, 'We've got bigger problems.' "

Jay van Oostdam, adviser in Health Canada's environmental contaminants bureau, says the department has to be careful in communicating the risk of mercury for fear of driving people away from nutritious fish. Protecting the traditional lifestyle of aboriginals is a major concern, he adds.

"We've got to be careful that we address the important health issues up there and we don't scare them off traditional foods and they have to buy expensive southern foods which are not as nutritious as their traditional foods."

Van Oostdam describes the mercury problem as minor compared with other public health issues. "It's very small effects. Fetal Alcohol Syndrome is probably much bigger problem than mercury."

But Donna Mergler, director of the Institute for Science and the Environment at the University of Quebec at Montreal, says the effects of mercury on fetal development are important, even if they're subtle.

"It's a collective effect that we experience as a society," she says. "It weighs on us as a society because you're going to have so many more kids with learning problems and fewer bright kids."

Dan McDermott of the Sierra Club says mercury deserves far more attention than it's had.

"It's brain poison, it makes you stupid," he says. "A society that puts up with it is complicit in its own decline."

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