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The science behind the advisory | Where does mercury come from?
Dispelling mercury myths and fears
Another fine reason not to eat loons
What about fish from restaurants and grocery stores?
Inside the walls of the State Lab of Hygiene, it's an eclectic assortment of rubber boots, white lab coats, fish guts and country music. At this office "getaway," Jim Amrhein, DNR fish contaminant specialist, performs his studies on Wisconsin fish. Like most anglers, he'd rather be catching tonight's supper instead of working, but Amrhein's proud of his role in protecting the health of Wisconsin's visitors and residents for the past 16 years.
Long-term studies by the Department of Natural Resources, the Division of Health and the State Lab on mercury levels in fish led to changes in the advice that Amrhein and his colleagues offer people about eating sport fish during the 2001 fishing season. First, the annual fish advisories now cover all Wisconsin inland lakes and rivers. Second, the guidelines on consuming fish are much easier to interpret.
Mercury levels haven't changed much in fish. In fact, levels have remained remarkably constant in waters where fish are sampled.
"What's changed is we're learning that mercury is more widespread in the environment, and we're concerned about exposure to smaller amounts of this contaminant," Amrhein explained. Fetuses and young children are especially susceptible to neurological changes and possible learning disabilities from continued exposure to even the small amounts of mercury in sport fish.
Our aim is giving people reasonable guidelines to continue enjoying the many benefits of eating fish while minimizing health risks throughout their lifetime, said Dr. Henry A. Anderson, chief medical officer for the Wisconsin Division of Public Health. To reduce mercury exposure, it's time to get a little more cautious by spreading out the number of meals of fish eaten during a week or month, particularly for pregnant women and young children, Anderson said.
"It's not a 'don't eat fish' advisory, but instead a guideline on how much to eat,"said Amrhein.
The mercury guidelines this year suggest that:
The science behind the advisory
In the past, mercury advisory levels were set one lake at a time following fish sampling by DNR, analysis by the State Lab and interpretation by the Division of Health.
Each year Amrhein sends fish managers a list of lakes that will be sampled. Using fyke nets or boom shockers, fisheries crews collect about 10 top-level fish, such as walleye and northern pike, of varying sizes from each lake on the list. It's safe to assume that if predators have low levels of mercury than other fish down the food chain, like panfish, will also have low levels.
The collected fish are frozen and shipped on ice to Madison. What looks like the preparation for a Friday night fish fry is actually the beginning of the contaminant research. Each fish is thawed and filleted.
Amrhein also records the sex of each fish, examines its stomach contents and includes the information in notes about each sample. Since mercury accumulates up the food chain, there is a direct correlation between what the fish eats and its mercury level. Unlike the contaminant PCB (polychlorinated biphenyl), mercury is stored in muscle. You can't trim away the skin and fatty portions of fish to reduce mercury concentrations.
An atomic absorption spectophotometer is used to detect
|What about fish from restaurants and grocery stores?|
Restaurants and grocery stores sell fish that is commercially raised in fish farms or commercially netted from rivers and the ocean. Some kinds of ocean fish have mercury levels on a par with walleyes, northerns and bass. Other species have even higher mercury levels. In fact, the U.S. Food and Drug Administration (FDA) has warned pregnant and nursing women not to eat shark, swordfish, king mackerel and tilefish because they contain higher levels of mercury (above one part per million).
On the other hand, ocean species that are the staple of Friday night fish fries – cod, ocean perch and haddock – are relatively lower in mercury, on a par with our panfish. These fish are unlikely to concentrate as much mercury because natural conditions in the oceans are less conducive to forming methylmercury that moves through food chains.
Farm-raised fish are also less likely to accumulate mercury unless the controlled pellet diet they receive contains high levels of mercury.
Commercially raised and harvested fish are inspected and regulated by the FDA News accounts suggest that bacterial contamination in handling fresh fish and moving them to market is a larger issue for commercial fish than mercury contamination.
The main source of mercury in the water is actually the air. Fine particles of mercury released from coal-fired power plants and other sources drift in the air, attach to fine water droplets and fall into lakes and rivers. The particles are so light that they can travel across several states before rain and snow wash them from the sky onto land and into lakes, rivers and streams. Some of the emissions falling in Wisconsin come from sources within the state, some from regional emissions; just as some of our emissions drift to other states and provinces.
Not all waters are equally susceptible to the damaging effects of mercury. In shallower waters with soft bottoms that become depleted of oxygen, mercury particles settle and are digested by bacteria that thrive in these low-oxygen conditions (anoxia). The mercury is converted to methylmercury that moves more readily into tiny plants and animals that fish feed on. It's this form of methylmercury that accumulates in food chains, fish and people.
Mercury is much more of a concern in inland lakes because the Great Lakes don't develop a low-oxygen zone near the lakebed and don't contain large numbers of anoxic bacteria. So the majority of mercury that falls in the Great Lakes is not converted to a form that would move through food chains. The same holds for ocean water. The oceans don't contain as many of the bacteria that could readily convert mercury into a form that is easily absorbed by living organisms.
"There has always been a small amount of mercury entering waterbodies and fish," Amrhein said, "but we're concerned that manmade sources add more mercury more quickly to the environment."
Under the Clean Air Act, utilities are required to meet standards to reduce the risks of inhaling mercury, but the act doesn't address the problem of mercury deposition on lakes. In response, DNR staff is drafting a rule to reduce mercury air emissions that will be presented to the Natural Resources Board this summer.
Amrhein is the first to see how mercury can accumulate in fish. So how come he is not afraid to catch and eat them? He knows the nutritional benefits of eating fish outweigh the risks when the guidelines are followed.
"When people put into perspective how much fish they eat per year, they will realize they probably don't have much to worry about," Amrhein said. "Most people already follow the advice without trying."
Eating a meal a week of panfish or a meal a month of game fish gives mercury a chance to get out of the body. Unlike PCBs, which accumulate over a lifetime, mercury is water-soluble and half the amount ingested will be expelled from the body within 70 days. Amrhein calls it the "everything in moderation advice." If fish are eaten in moderation, mercury in the blood will not reach harmful levels.
"Most of us know from our upbringing that too much of anything can be harmful," Amrhein said. Since 1971, DNR and the Division of Health have partnered to offer the angling public advise on which fish could be eaten freely, which should be eaten in moderation and which should be avoided to reduce the risks of the environmental contaminants mercury and PCBs. Even though updated advisories were produced and publicized every year, "we want to create awareness, but we don't want people to misinterpret the advice and stop eating fish," Amrhein said.
Although Wisconsin took greater efforts than other states did to alert its anglers, only a third of people in angling households, and fewer immigrants knew about the advisory. Clearly, the annual publicity wasn't enough and the information was difficult to interpret for many people.
Now, the Department of Natural Resources has partnered with the Division of Health to create a campaign called "Hook Into Healthy Fish." Funded by grant money, the campaign aims to promote awareness of mercury issues without creating undue alarm.
The DNR is taking the "Hook Into Healthy Fish" campaign to Women, Infant and Children (WIC) groups, minority groups, especially those that don't speak English as their primary language, tribes, and angling associations. Instead of just relying on information in written advisories, the healthy fishing message will be printed on coffee cups, T-shirts, posters, magnets, perhaps children's sippy cups, bibs and other props. It is hoped that the promotional items will make their way into doctors' offices so people can get advice from their physician in addition to contacting the Department of Natural Resources.
The team also plans to work with the Great Lakes Indian Fish and Wildlife Commission, tourism outlets, electric utilities, fishing guides, physicians and health maintenance organizations to spread the word wider about the simpler health advice for the fish-eating public.
One partner, Richard "Moose" Speros, secretary of the Wisconsin Department of Tourism, has already commended the streamlined approach for being honest and straightforward.
"That's quite an endorsement given that Mr. Speros is not only the head of tourism, but owns and operates a resort and is a lifelong angler," Amrhein said. "We understand, as he does, that discriminating anglers want advice on which fish in their catch are safest to keep and eat."
The DNR also published a revised advisory booklet this spring that included the new guidelines about mercury in fish and continued PCB advisories that are still listed for individual waters that have been tested. These booklets can be picked up at DNR service centers and ranger stations. All of the information is also listed at Department of Natural Resources.
|Another fine reason not to eat loons|
Loons, of course, are a protected species, are not eaten by people, and are a true joy to watch on the water. According to DNR mercury researcher Mike Meyer, loons may also be the ideal animals to study to measure the spread of mercury through animal food chains. Loons accumulate more mercury than most fish or other animals for several reasons: