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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

February 1998

Loon and young. Loons can accumulate mercury in their flesh from the fish they eat. Mike Meyer, © 1998
Loon and young. Loons can accumulate mercury in their flesh from the fish they eat.

© Mike Meyer

The metal that slipped away

The costs of reining in the ubiquitous spread of mercury are high. The costs of not reining it in may be higher.

Katherine Esposito

Loons as sentinels || Seeking the truth || How mercury moves
How much mercury is too much for people?
Reducing mercury emissions || Merc work

Broken Bow Lake is as charming as they come in northern Wisconsin. Only six miles from the Lac du Flambeau Indian reservation, its 300 acres are surrounded by oaks and pines, in which eagles perch scouting. Its serene, transparent waters are interrupted twice by small wooded islands. And on one of those oases, a female common loon and her mate have prepared a nest each year since 1992.

In the nest, scratched together from lakeweeds, bulrushes, and mud, the same female, known by the color bands circling her legs, laid two eggs every spring.

But chicks have been seen only twice. The first year, 1992, neither egg hatched. In 1993, the pair hatched twin eggs, and one of the nestlings was discovered, lost, clear across the lake. A soft-hearted field technician prevailed on DNR researcher Mike Meyer to reunite the four. The following year, the same thing happened, and this time, nature was allowed to take its course. The chick disappeared. By the time someone later checked on the last one, it, too, was gone.

Since then, three years running, not a single loon chick has survived to migrate from Broken Bow Lake. They may have hatched, but none has ever been seen. What has been found in the female, however, are strikingly high levels of the toxic metal mercury, in a form, called methylmercury, that can reside in body tissues and blood of animals.

It could be an anomaly, a complete coincidence. There could be a logical explanation for the missing chicks, or it could be a series of mishaps. But the female loon on Broken Bow Lake does fit into a larger, dispiriting picture, one taking place all across North America east of the Rockies: fish in thousands of lakes and reservoirs, and the wild creatures that eat them, are showing up with mercury in their bloodstreams.

Mercury matters because excessive doses are known to damage the human nervous system and cause irreparable harm to the brain. Smaller, chronic, doses can also be trouble, especially for a developing fetus. Severe poisoning episodes in Minamata, Japan in 1956 and Iraq in 1971, in which hundreds of people died and thousands more, were permanently injured, form the most shocking examples of mercury's toxic potential. Today, finding mercury in a rustic setting, six hours from Chicago, has scientists scurrying to learn where it is coming from and what damage it is doing to all animals, humans included.

Some scientists support controls now. Minnesota's Edward Swain, a mercury specialist with the Minnesota Pollution Control Agency and principal author of a report documenting increases in Midwestern mercury fallout rates, is among them. "Research is interesting and important, but the basic knowledge is already there. There's too much mercury in the environment," he says. "The big picture isn't that difficult, so the overall decision isn't that difficult."

But Meyer, whose latest research is being published this month, believes that policy decisions should be based on firmer conclusions.

On a sparkly fall day, less than an hour's drive southeast from Broken Bow, the setting sun frames a second study lake. Called Washburn Lake, it also shelters loons, but something here is different: the birds here have raised five generations of chicks to free-flying adulthood. "It's one of our most successful pairs," Meyer says.

The truth, he argues, is that we really don't know if mercury is causing those chicks on Broken Bow Lake to die. Other scenarios are just as likely.

"It could be, every year an eagle comes in to take and eat the young while we're not there," Meyer continues. "I don't think the data for wildlife is sufficient to make a case one way or another. But I think it's plausible it could be having an effect."

Loons as mercury sentinels

Gavia immer, the common loon, a lifelong fish eater and beloved lake resident, seems at particular risk. With its haunting, trembling wail, it steals our attention on warm summer nights, superimposing its songs on those of crickets and cicadas. With its stiletto-sharp beak and its diving and underwater swimming prowess, the loon leads a simple life, needing little but unblemished shorelines and clean water. To the dismay of many, though, we don't seem to be keeping the water as clean as we thought.

Loons are considered sentinel species for mercury contamination in Wisconsin, though high levels have been found in other fish-eating animals, including mink and otter. Now, studies from all over are pointing to certain patterns of mercury pollution.

Mercury concentrations in wildlife slowly decline, it appears, as one traces a line from the wilds of eastern Canada all the way west to Alaska. In Nova Scotia, in Kejimkujik National Park, "frightening" levels of mercury are found in some loons, says Joseph Nocera, a graduate student studying loon behavior and toxicology at Acadia University in Wolfville. The pristine 89,000 acre park, 40 miles from the Atlantic Ocean, is known for its many sphagnum bogs fringed by pines and darkened by natural tannic acid. Here, loons are having more trouble reproducing than anywhere else, Nocera contends.

In New Hampshire and Maine, contaminated lakes and wildlife are also being scrutinized. From there to the Midwest, the amounts found in wildlife gradually lessen, though the element in some Wisconsin birds approaches Nova Scotian levels. Alaskan loon data show only tiny amounts of mercury.

In southern Florida, other fish eaters such as great egrets, great white herons, great blue herons, roseate spoonbills, wood storks, and anhingas all have been found to have mercury in feathers, livers, or eggs. Much larger predators, too, have been affected.

Ironically, more loons than ever are being born in Wisconsin. From 1990 to 1995, their numbers rose from 2,600 to 3,200. But mercury's presence in our waters is a subtle and troubling challenge. If the work of Mike Meyer and others indeed shows that mercury pollution genuinely is causing many wild animals to be less fruitful, it reverts to policy makers to decide if we should do something about it.

Seeking the truth in the environment and wild foods

Meanwhile, we don't know whether humans most at risk – young children and fetuses – are being protected from mercury's harm. In Wisconsin and 39 other states, special advisories are issued to fish eaters, suggesting how to assess risks before eating certain fish from mercury-contaminated lakes. These include identifying the fish species, measuring the fish, and reading the chart. It's easy, but many people aren't that diligent. In other countries, children and mothers dependent on fish may not have the food choices nor the scientific information to avoid possible exposures.

Internationally, the scrutiny of mercury in our environment has reached unprecedented heights. In the Indian Ocean's Seychelle Islands and on the Faroe Islands off the coast of Norway, separate studies of children born into a fish-eating culture will be reported soon. In the United States, the Environmental Protection Agency's much-anticipated eight-volume, 1,700-page Mercury Study Report to Congress, is expected to be completed this winter with several Wisconsin researchers among the reviewers. In the Midwest, the EPA's Great Lakes National Program Office is dedicating considerable effort to a regional mercury reduction strategy.

Many private groups are also looking for answers. The research arm of the utility industry, the Electric Power Research Institute, has been spending millions for studies on mercury in rivers and lakes, and ways to control mercury emissions, if required, from coal burning. Meyer's studies and others have been supported by businesses, agencies, and environmental groups. Those include the Wisconsin Acid Deposition Research Council, the U.S. Fish and Wildlife Service, the North American Loon Fund, and the Sigurd Olson Environmental Institute.

With so many people fingering the pie, one onlooker already expects vigorous debate as these reports begin to circulate. Says Doug Knauer, a DNR research manager, "It's going to be an interesting time, the next 12 months."

How mercury moves

Since the mid-1970s, biologists sampling fish in northern Minnesota and Wisconsin have found mercury in high levels, but they didn't know where it was coming from. It took a decade of inquiry to determine it was coming from the air, especially from distant coal-burning power plants and waste incinerators – not swirled into riverwaters from chemical discharges, not drifted down from an industrial smokestack, because none existed for hundreds of miles.

Mercury is found in coal and wood burned to create electricity.

© Robert Queen
A smokestack. Mercury is found in coal and wood burned to create electricity.

Instead mercury attaches to tiny raindrops that settle after one or two years of floating in the atmosphere.

It's reminiscent of the nation's struggle with acid rain, which also sullies some of our cleanest, most remote lakes. In fact, it was acid rain research that first showed scores of fish tainted by mercury.

Lakes that are more acidic contain bacteria that convert mercury falling from the sky into methylmercury – an organic form that is easily absorbed by the tiniest plants and animals. On its spread through the food web, mercury levels rise in each predator. This process, called bioaccumulation, can result in a level of mercury in the topmost predator up to 10,000,000 times greater than the original amount in surrounding waters.

Beginning around 1990, scientists realized lake acidity wasn't the only important factor at play – it was the bacteria that thrived in those waters. And the same bacteria can live in less acid environments if certain conditions are present. Those include low oxygen levels from decomposing plants and higher sulfides. The best places to find such conditions are in wetlands. So if a lake or river has a wetland feeding water into it, the water will frequently be tainted with methylmercury.

Lakes in Nova Scotia, however, tell their own story. Most have received higher doses of acid rain and mercury than their Midwestern counterparts, swept by prevailing winds from hundreds of industrial sources. Most haven't any limestone to naturally buffer acid water. And when those conditions combine with natural tannins, the mercury levels in fish and wildlife can climb through the roof.

Wisconsin has its own unique scenario. Some lakes are not acidic at all, but receive their water from wetlands, with an abundance of methylating bacteria. Others can blame it on their geologic settings. In the north, almost half of our lakes receive most of their water from the sky, and very little from groundwater because they are perched high above the water table. If the rain and snow are acidic, the lake's chemistry becomes more acid. But five miles away, a lake set lower in the earth which receives more of its water from the ground and less from the air is likely to be less acid.

A pattern emerged, one in three of the 3,000 Wisconsin lakes that have been tested received a mercury warning. Twenty to 30 more lakes are added to the warning list each year. The rest of the state's 15,000 lakes are too small to be fished often, and so they aren't being checked for mercury, according to the DNR officials.

Meyer first showed that Wisconsin loons that made their homes on more acidic lakes carried higher blood mercury levels than those which nested on less acidic lakes. In a subsequent 1992 study, his team examined hatching and survival rates for chicks. Dismal results at Broken Bow Lake, gave them part of their answer. Washburn Lake, where loons raised chicks successfully, is one of the less acidic waters.

Meyer can't say for certain that mercury is directly responsible for the loons' reproductive failure or the chicks' deaths. It could be that acidic lakes spawn fewer fish for loons to eat. Clearly, he said, loons accumulate mercury for a while before it affects their reproduction. And it takes a lot less mercury to cause these kinds of problems than it does to poison adult birds.

How much mercury is too much for people?

Severe poisonings in Japan and Iraq show that people can be poisoned and killed by mercury, but we don't know what happens when adults, children and fetuses are exposed to tiny doses over a long time.

Regulators have assumed that people who like fish don't eat too much of any one kind. But in 1994, one Dane County couple and their toddler who ate storebought fish for dinner three to four times a week threw that assumption out the window. After requesting a mercury blood test, each was found to have elevated blood mercury levels but none showed symptoms of poisoning. Seabass imported from Chile, was found to be the cause, according to Lynda Knobeloch, a state health toxicologist. Mercury contained in the seabass was below federal limits, but the entire family ate enough fish to accumulate the toxin in their bodies.

After they ceased eating the fish, the family's mercury levels dropped. That is usually what happens. Small, steady doses of mercury are excreted from the body in about three months. But the case illustrates the scary side of the mercury issue, suggesting that existing laws may be inadequate.

No one knows if other people are receiving regular doses of mercury. In the case of lead, which also can harm the nervous system, doctors test children fairly routinely and use a certain blood level as evidence of poisoning, says Dr. Henry Anderson, Wisconsin's chief medical environmental officer. No such reference for mercury exists, however. So it's up to physicians to suspect something in a child's behavior or ask about possible exposure.

Lots of people in Wisconsin occasionally eat game fish, but doctors wanted to query those who eat a lot of fish to see if they show any symptoms of mercury poisoning.

In 1990, a team from Madison surveyed five Chippewa tribes to find whether walleye spearers and their families were being dosed with hazardous amounts of mercury in the fish they ate. The inquiry was spurred, according to Dr. Marty Kanarek, UW-Madison associate professor of preventive medicine, because there had been reports of hand tremors among the Chippewa. Researchers wanted to know whether the known mercury contamination in the walleyes was reflected in Chippewa blood tests, and what kind of threat that posed.

Tests showed those Chippewa eating a lot of walleyes had higher blood levels of mercury, but the levels were far below those that cause overt disease. But excessive alcohol and tobacco use and diabetes are known to cause sickness and trembling, and these conditions were documented among the Chippewa by the same panel in a different study. Whether mercury intake contributed to these factors to produce health consequences is anybody's guess.

Researchers noted that spearfishers seemed to avoid lakes they knew were on the state's mercury advisory, reducing their potential exposure. That underscores the value of the advisories, according to Kanarek. "As long as they [followed] the guidelines, everything was fine."

Limiting human contact with mercury-tainted fish is one way to prevent a possible disaster. But loons can eat up to 1,000 pounds of fish in a season. "Here's a resource at risk," says Doug Knauer. "They don't have any choice. They can't read that they shouldn't be eating fish out of these lakes. They just eat the fish, and eat a lot of it." If they are jeopardized, he wonders, how will we protect them?

Reducing mercury emissions

Wisconsin does have a plan. For the next few years, however, it will be entirely voluntary. Last fall, the DNR formed a "stakeholders" study group, to look at ways to control mercury emissions from different segments of society. In charge is Lynda Wiese, from the Bureau of Cooperative Environmental Assistance. Anybody with an interest in the issue can participate, representing those who need and use mercury, find it in their emissions, or are concerned with environmental effects.

In her windowless downtown Madison office, Wiese glances at the bright lights, and shrugs. Gradually, across the nation and in this room as well, incandescent bulbs have been replaced by energy-saving fluorescent tubes, and society has patted itself on its back. Now, we find that the mercury in these lights, about one-tenth the amount in a fever thermometer, is leaking into the air every time a lamp is broken, which commonly happens when they are tossed out. If we decided to return to incandescents, Wiese figures, we'd wind up burning more coal to produce as much light as a fluorescent.

That wouldn't be wise. Coal-burning power plants already account for more than a third of all Wisconsin mercury emissions. The federal Environmental Protection Agency is now studying toxic materials in utility emissions across the nation. Computers are modeling where mercury from a power plant goes after it leaves the stack, and how much it would cost to collect it. According to an estimate from the Electric Power Research Institute, removing one pound of mercury from a coal smokestack could cost $40,000. That compares with $1,000 or less to remove a whole ton of nitrogen oxide from a similar stack.

Ironically, no federal limits now exist for mercury in utility emissions, and those covering industry are extremely generous – the limits are set higher than the actual discharges. In fact, Vulcan Materials, in Port Edwards on the Wisconsin River, evaporates 1,100 pounds of mercury every year making caustic soda and other chemicals for paper production. That's close to half the total from all Wisconsin utilities combined and one-fifth of all Wisconsin mercury emissions. The mercury vapors which leak through doors and windows to the outside air, are legal because years ago, little was known about the dangers of methylmercury or how mercury can spread. As more has been learned, some sources such as municipal and medical waste incinerators have been required to control mercury in their emissions. And it has been removed as a component of latex paints and fungicides.

After concluding that much of that state's mercury is coming from landfills, Minnesota's Mercury Task Force banned the disposal of certain mercury-containing devices in 1992. Fluorescent lights, thermometers and thermostats, electric switches and more, all known to harbor minute amounts of mercury, must now have it removed before they can legally be thrown away. In 1990, mercury batteries also were banned from landfills, and no longer may be sold in the state.

Minnesota's stakeholder study group has developed incentives to reduce emissions even further. Some suggestions include fees on mercury disposal, emission limits for landfills and utilities, and a "cap & trade" approach, whereby an industry reducing its emissions below a capped level can sell the amount of the reduction to a second industry.

Wisconsin has also banned mercury in most batteries and in children's toys. But for now, most attention will center on ideas like recycling those fluorescent lights and finding substitutes for other small sources of mercury.

Many people are completely unaware that mercury is so ubiquitous, says Alexis Cain, EPA's mercury coordinator. "Emissions from coal burning are a more significant source, but deliberate use [of mercury] is sort of a low hanging fruit," and can be curtailed first, he explains.

Finding substitutes for mercury would be easier if the price of raw mercury reflected its treatment and disposal costs. The metal has been sold from federal stockpiles for as little as $1 a pound – hardly an incentive to use alternatives.

Meanwhile, scientists recently returned from China are concerned that the mercury drifting in the atmosphere and sprinkling into Wisconsin waters indeed may be coming from that country and others like it, as they modernize as cheaply and quickly as possible. Unfortunately, cheap and quick can mean older, polluting technologies, such as the kind used by Vulcan, rather than newer, cleaner ones. That presents a quandary – should the Midwest and the nation invest its time and money on an international issue that other countries might choose to ignore?

Perhaps we should start the search closer to home.

There are no industries near the northern Wisconsin lakes where mercury is drifting in, notes Doug Knauer. We speculate it can originate in a distant land and float for years before settling here. Many also wonder if mercury contamination is more regional. Perhaps more of our mercury is coming from Midwestern power plants and incinerators and traveling shorter distances before reaching our lakes.

"You can't take a mercury sample and say where it's coming from," Doug Knauer says. "We have an idea how much is emitted by industry in each state. But we don't know how much falls locally. We're guessing." Where new power plants are sited could be influenced by those answers, as well as which ones should be outfitted with costly emission controls, he adds. The DNR and other groups are seeking money to focus on the Lake Superior basin to track mercury's fate after it leaves a stack. The U.S. Department of Energy, the EPA, EPRI, and several Canadian agencies are interested, too, according to Knauer.

As part of the global community, our responses to such challenges can contain small sources like fluorescent lights, and provide strategies to curtail larger sources like cleaner coal combustion.

"You've got to clean up your house first," Knauer says. "You can't be out there preaching control strategies unless you clean up your own act in your own back yard."

Merc work

One would hope a human mother would be a little suspicious if she came home and found a pink baby doll substituting for her infant.

But loons aren't quite that smart. After Mike Meyer left a plastic Easter egg painted Army green and filled with a tiny balloon of warm water in a nest last summer, the loons didn't notice any difference. Fishers and raccoons tried to make a meal of the egg, and left a pitiful relic behind. But the loons still didn't comprehend.

When the real chick, incubated in a warm lab for two weeks, was returned, nestled and peeping in a wet paper towel, its parents bustled from the water to welcome it into the world.

Loon eegs kept warm and cozy in transit to the incubator.

© Mike Meyer
Loon eggs on the way to the incubator.

Unfortunately, its stay was not long. A hungry fisher came back, and this time, found something much tastier than a plastic egg.

The only way a scientist could know what truly happened to that single loon egg on a single water – in this case, the Turtle Flambeau Flowage – would be to spend a great deal of time there and imbed radio transmitters in the birds. And that is what Meyer and a colleague, Kevin Kenow, a waterfowl biologist with the US Geological Survey, did. The two men want to figure out exactly why some loon chicks die and some live in northern Wisconsin lakes. Do they die from mercury? Or are there other routine pitfalls in a loon chick's universe?

It can be exhausting work. Each of 14 chicks, hatched in last summer's pilot program had its blood drawn, had a transmitter placed in its chest, and was settled in the nest within six hours of its birth. "We underestimated the amount of effort," Meyer chuckles.

This is the first time that researchers have been able to monitor loon chicks so closely before and after hatching. The radio signals track the birds' movements. If the chick survives to eventually fly off, the transmitters help Meyer to know where it is. Next summer, the goal is to monitor 40 lakes and collect 20 to 25 eggs, he says.

Meyer hopes this work will provide the proof that other studies have lacked. "The bottom line is, to tease out the effects of mercury, Meyer says. "Loon nests fail for lots of reasons. Over one-half of eggs laid in any given year do not hatch – they're eaten by eagles, raccoons, or skunks. Sometimes the nests get flooded. Sometimes they're abandoned if human disturbances are too great."

In addition to the loon studies, the DNR has other programs devoted to addressing mercury issues. Just a few of these include:

  • the Water Division is investigating the idea of a special status for Lake Superior, that would restrict future mercury loadings;
  • the Air and Waste Division is evaluating mercury emissions from landfills;
  • the Water Division is returning to lakes sampled 15 years ago, to check on mercury levels in walleyes;
  • the Enforcement and Science Division is cooperating with other federal agencies to research mercury in rivers and the Florida Everglades;
  • the Water Division is developing municipal mercury reduction programs for Milwaukee, Madison, Green Bay and Superior;
  • the Cooperative Environmental Assistance program has a business expert promoting mercury pollution prevention among energy producers, hospitals, and dental labs.

Additionally, the DNR has a manual, "The Mercury Sourcebook," containing a wealth of information to help communities reduce mercury use.

Katherine Esposito writes about environmental issues from the WNR office in Madison.