Heavy Metal:
Are people, fish, and wildlife threatened by mercury?

At a junior high school in Ohio late last summer, custodians cleaning up after the removal of old lockers found the substance on the floor.
It was a small amount—one to three teaspoonfuls, according to the Akron Beacon Journal—and school wasn't open, so no children were exposed. But no chances were taken. City, county, and state public safety, health, and environmental officials went to work. A public meeting was called to address citizen concerns and tests were conducted over two days before the all-clear was issued.
Several weeks later it happened again. Another small amount of the substance was found, this time in a Wisconsin movie theater. Patrons were kept away and the theater was closed while a hazardous materials team cleansed the contaminated area.
Anthrax planted by Al Qaeda?
No, it was mercury—in the Ohio incident, a dusty blob of metal that evidently hadn't been disturbed in years; in Wisconsin, a tiny release caused by the malfunction of a popcorn machine.
In each episode, the media quickly pointed out that no one was harmed; it was welcome and perhaps unexpected news, given the frightening stories about mercury reported somewhere almost every day.
Those stories aren't really about misplaced souvenirs from 1950s Ohio chem-lab experiments or the escaped contents of Wisconsin electrical switches. They're about coal.
Coal fuels big power plants, and its combustion releases mercury. Once out of the smokestack, it can fall to earth nearby or float on air currents for thousands of miles and months on end. In a lake, organic activity may change some of it to methylmercury—toxic in sufficient doses—and some portion of that can get into the food chain, eventually eaten by fish that may later be eaten by people. In fact, a fish without some mercury in it would be very hard to find.
The critical question is: How much is too much? Methylmercury is a recognized threat to the nervous system and may delay development in young and unborn children.
At the extreme, mass poisonings have occurred. In the 1950s, thousands of Japanese were sickened and hundreds died from massive doses they consumed in seafood taken from waters polluted by the direct dumping of mercury-laden industrial wastes. In the 1970s, thousands of Iraqis were poisoned and hundreds succumbed when wheat intended for planting and treated with a mercury-based fungicide was mistakenly ground into flour and baked into bread.

Real Evidence Rare

But absent gross abuse or horrible mistakes, examples of harm to people are demonstrably rare. Researchers have gone looking specifically for harmful effects and failed to find them in studies of both people and wildlife. Not because mercury is benign but presumably because it takes an uncommonly large dose to do damage, and perhaps as some researchers have speculated, because other dietary factors mitigate the effects of mercury. It’s more than a little bit interesting that two studies with different outcomes suggested a mitigating factor may be the frequent consumption of fish.
One major study was conducted in the Faroe Islands, Danish territory north of Scotland. There, in the most worrisome findings concerning dietary mercury’s effects, researchers concluded that each doubling of an unborn child’s mercury exposure “may cause a developmental delay of approximately two months for several functions.”
The Faroes study is the one government health warnings in the U.S. rely on. Published in 1997, it analyzed the neurological development of more than 900 Faroese children at approximately age 7.
Faroese mothers and their unborn children are exposed to methylmercury through consumption of large quantities of pilot whale meat. Researchers said “a discernible, insidious effect seems to be present” below what were considered safe exposure levels, but they also acknowledged that pilot whale meat is cross-contaminated with PCBs (polychlorinated biphenyls), which can mimic the effects of mercury toxicity.
Alongside their concerns, the Faroe researchers suggested the children had been protected against low birth weight and developed excellent visual systems through their intake of seafood. “Accordingly, the reliance on a seafood diet could perhaps compensate for or counteract some adverse effects due to methylmercury,” their report said.
A University of Rochester study followed more than 700 children in the Seychelles Islands for more than a decade. A 1998 university news release reports no evidence of harm in this Indian Ocean society, “where most people eat nearly a dozen fish meals each week and [exhibit] mercury levels about 10 times higher than most U.S. citizens.”
“Indeed, no harmful effects were seen in children at levels up to 20 times the average U.S. level," the release continued, referring to the study published in 1998 by the Journal of the American Medical Association. The release went on to warn that regulatory actions reducing recommended safe levels of exposure “might also convince consumers who associate mercury with health dangers to limit their intake of fish, a remarkably healthy form of nutrition.”

Agencies Act Anyway

Two years after the Rochester scientists cautioned against regulatory overreaching, the Environmental Protection Agency (EPA) slashed its official safe-consumption level for mercury. The Wisconsin Department of Natural Resources (DNR), which had seen a mercury regulation bill die in the Legislature the prior year, followed suit early in 2001, adopting a safety standard one-tenth the previous level. Announced on Ash Wednesday when many of Wisconsin's large Catholic population traditionally increase their fish intake for the six weeks of Lent, the move put every inland lake in the state under a consumption advisory. More than 15,000 Wisconsin lakes now officially held dangerous fish, up from 341 the day before. Predictably alarming headlines appeared.
Considering all this, human health data from Wisconsin is strikingly thin.
More than two years into an often intense discussion as the DNR seeks to regulate mercury without legislative help, proponents of the regulation have offered a single Wisconsin case study involving a family of three who in 1994 experienced abnormally high bloodstream mercury levels after eating imported sea bass twice each week for several months.
The husband reported sleep disturbances and trouble concentrating.
“Other than the sleep and concentration difficulties reported by [the husband],” the 1995 study said, “none of the family members exhibited clinical symptoms of mercury toxicity.” Later, it adds, “While no overt clinical symptoms were observed in these individuals,” the husband's complaints “are consistent with the neurotoxic effects of methylmercury exposure."
Wildlife is getting more attention. Early in 2002, University of Wisconsin and DNR scientists gave their first report on the findings of a two-year study of common loons. A captive population of about 60 of the fish-eating birds received a diet containing mercury up to three times the concentration they'd likely consume in the wild, and showed no symptoms of mercury toxicity.
But today, fish advisories propel a drive by the DNR to eliminate 90 percent of mercury emissions from Wisconsin power plant smokestacks over a 15-year period.
They’re going to be disappointed. Not by a lack of regulatory power, which they’ll probably obtain, but by the results.

It’s Everywhere, It’s Everywhere

Mercury is an element, one of the basic things the Earth is made of. In the words of Bill Kowalski, a chemist at La Crosse-based Dairyland Power Cooperative, “It’s everywhere. Just about anything you touch has some mercury on it or in it.” Kowalski’s work involves environmental testing to make sure Dairyland complies with state and federal regulations, and he described the rigorous cleanliness standards needed to ensure valid sampling:
“When you’re talking parts per trillion, the personnel involved, the garments they’re wearing, the glassware they use, all those things can affect the sampling,” he said. “If you have silver amalgam fillings in your teeth, you basically have a mouth full of mercury and breathing into the bottle will contaminate your sample.”
Kowalski recalled earlier research on copper emissions and the dramatic impact when samplers began having doors opened and closed for them by other people. “The copper content dropped about 50 percent after the samplers began to avoid handling brass doorknobs,” Kowalski said.
Like other coal-burning electricity providers, Dairyland has ample reason to be concerned about accurate testing and also about regulation getting results. Costs must be passed on to distribution co-ops served by Dairyland—and finally to their members—so it matters that regulations perform as advertised.
And it matters that the obvious alternative to coal-fired generation—natural gas—is hobbled in Wisconsin by limited pipeline capacity. And it also matters that many of those who dislike coal surely will oppose new pipelines as well as gas-fired plants because they emit carbon dioxide. Even wind turbines face strenuous opposition, and more than a thousand of them would be needed to replace Dairyland's existing generation capacity.
Dairyland says it can’t estimate the cost to reach the full 90-percent reduction because it doesn’t know how that would be achieved without closing and replacing power plants. But reaching the 50-percent reduction prescribed by the DNR at the 10-year mark will add expenses of $20 million annually, the co-op estimates.
The regulation would also trigger an environmental problem all its own, according to comments filed last summer by Dairyland with the utility-regulating Public Service Commission of Wisconsin (PSC). The most promising—if hugely expensive—technology for removing mercury from smokestack emissions involves injecting activated carbon into the flue. Dairyland’s comments to the PSC warn that will end a recycling program using fly ash in road building.
“Dairyland does not believe the carbon-adulterated fly ash will meet the quality standard that is expected in the market, and may force Dairyland to landfill its fly ash instead of recycling the fly ash for construction projects,” the document says.
The document is silent on the difficulty of siting new landfills and on the prospect that fly ash containing mercury-contaminated carbon might require disposal in landfills certified to accept hazardous waste.

Puny by Comparison

Environmentalists often claim power plants are the biggest source of mercury emissions worldwide. Power plants probably are the biggest source associated with human activity, but they're puny contributors compared with Mother Nature.
Half the mercury emitted to Earth’s atmosphere is released by natural sources beyond the reach of government regulation. These include vaporization from rocks, soil, and oceans; combustion of vegetation in forest fires; and volcanic activity.
Of the remaining half, roughly 1 percent comes from power plants in the U.S.
Roughly 2.5 percent of that 1 percent is emitted by power plants in Wisconsin—that is, by the only sources covered by the DNR’s proposed regulation.
The covered emissions total about one ton annually. That's approximately 1/800th the annual worldwide emissions from biomass burning as estimated last year by the federally funded National Center for Atmospheric Research.
Factoring in the uncontrollable variety of sources is not so much like going through a series of step-downs in regulatory effectiveness, as it is like plunging headfirst down 50 or 60 flights. A molecule of mercury in a Wisconsin walleye could almost as easily have come from a volcano in the Philippines, a wildfire in California, or a rock on the bottom of the lake as from a power plant in Wisconsin. When all the unreachable emissions are set aside, there isn't much left to reach.
And then there's the stuff that's been around forever.
Sedimentary records indicate that before any industry existed in what's now Wisconsin, fish living in northern lakes would likely have contained enough mercury to bring them under a government health warning, applying today's standards.
Dave Cravenhoft of the U.S. Geological Survey made a particularly telling statement in remarks broadcast this March by Wisconsin Public Radio. Reporter Gil Halsted said Cravenhoft was leading research “to find out how much of the mercury in lakes has been there for more than a hundred years and is just recycling through the system, and how much is new mercury being deposited from new emissions each year.”
Cravenhoft told the reporter, “We have to know whether the new mercury is equally contributing, more contributing, less contributing. If we don’t get at those questions, in my opinion we can’t prescribe effective ways to deal with the issue.”—Dave Hoopman