hill country observerThe independent newspaper of eastern New York, southwestern Vermont and the Berkshires




Mercury threat persists, studies show

Health risks linger in region despite cuts in emissions



Contributing writer


Despite tougher pollution standards that have led to a sharp reduction nationally in emissions of airborne mercury, several new studies suggest that high concentrations of the toxic heavy metal are persisting in the environment and continuing to pose a health threat to people in the Northeast.

The new studies, conducted variously by the U.S. Environmental Protection Agency and several independent research organizations, include findings that even low levels of mercury exposure can lead to learning disabilities in children -- and that women of childbearing age are being exposed to just as much mercury as they were a decade ago, despite the unprecedented pollution controls adopted in recent years. 

Some environmentalists and public health officials say the studies suggest that mercury pollution is increasingly a global problem, with emissions cuts in the United States being offset by the proliferation of coal-fired power plants in China and elsewhere. A pending international treaty could help to reduce global mercury emissions but probably won’t take effect until at least 2020.    

Meanwhile, the EPA America’s Children and the Environment report, released in January, shows little progress has been made in limiting the average mercury exposure in women of childbearing age. Across a 10-year span, the report found, the median amount of mercury found in the blood of women ages 16 to 49 remained unchanged at 0.8 micrograms, despite a host of pollution controls that has cut domestic mercury emissions by 40 percent since the mid-1990s. 

Mercury is a powerful neurotoxin that is easily passed from mother to child in utero, and current EPA standards say that children born from mothers who have more than 5.8 micrograms of mercury in their bloodstream are at an increased risk of learning disabilities. Although the largest share of airborne mercury emissions are produced by coal-fired power plants in the Midwest, the EPA study found that New England residents on average are most at risk of elevated levels of mercury in the bloodstream.

Although the median mercury concentration of 0.8 micrograms per liter of blood found in women of childbearing age may not be close to the EPA’s threshold for concern, a recent Massachusetts study suggests that adverse health effects might occur at a much lower threshold. That study, completed last year by the Boston University School of Public Health, examined blood samples collected in New Bedford, the home of a Superfund cleanup site, and found that a child’s risk of developing symptoms of attention deficit hyperactivity disorder increased by 40 percent to 70 percent when mothers had mercury exposure of 1.0 micrograms per liter or higher, just 0.2 micrograms per liter higher than the national median level found in the EPA study.    

New England most affected

Concern about exposure to mercury is particularly strong in New England, which deals with more than its fair share of mercury despite strong regional efforts to curb air emissions and reduce or eliminate the use of mercury in consumer products. Past studies have shown high concentrations of mercury in the Deerfield chain of lakes in southern Vermont and in several lakes and reservoirs in the Berkshires.

Mercury often disperses far from its source, and much of the pollution that affects New England is carried by the prevailing winds from the Midwest, said David Evers, executive director of the Biodiversity Research Institute in Maine.

The institute, which has studied mercury pollution in the Northeast extensively, has found that although mercury is ubiquitous in the environment, what may be more important is the way regional ecosystems react to mercury. Some ecosystems, especially the acidic, high-elevation lakes and forests of New England, quickly convert mercury into an organic form that enters the food chain more readily, Evers said.

“New England is a very sensitive landscape to mercury input,” Evers said.  “You don’t need a lot of mercury falling from the sky to have problems.”

The easiest way mercury can jump from groundwater to the human body is through fish consumption, he said. That’s why state health officials across the region have for years been posting warnings urging women who are pregnant or might become pregnant to limit or avoid eating fish from local lakes and rivers.

Over the past decade, however, mercury levels appear to have remained steady in women of childbearing age.

That’s not because of a lack of outreach, said Sarah Vose, a toxicologist for the Vermont Department of Health. Doctors across the region have been diligent about informing pregnant women about the potential dangers of local fish consumption, she said. And women are heeding the warnings, she said.

“Pregnant women are somewhat hyperaware of things they should be worried about,” Vose said. 

But the EPA report concluded that women from the Northeast have the highest median blood levels of mercury in the country.  There may be several reasons for that, the report suggests, including that mercury levels in humans are highest near the coast, where fish is more readily available and more a part of the culinary landscape.

Another possible reason for the finding is the rise in mercury emissions elsewhere around the globe, environmentalists say. Fish consumed in the United States often come from international markets, and studies suggest the mercury concentrations in fish vary widely depending on the source.

Last year, for example, the Vermont Public Interest Research Group, Massachusetts Clean Water Action and seven other environmental groups tested samples of tuna sold for school lunches.  Larger fish, like tuna, often accumulate higher concentrations of mercury, but the groups found that mercury levels in tuna varied widely depending on where the tuna was caught. Tuna caught off the coast of Ecuador, for example, had three times the concentrations of mercury found in tuna caught in U.S. fisheries. 

Evers said that conclusion makes sense to him. A study co-authored by the Biodiversity Research Institute found dozens of global hotspots where mercury deposition is much higher than average because of proximity to coal-fired power plants, gold mining and other localized human activity.  The levels of mercury in fish near these hotspots can spike, Evers said. 

Many non-governmental organizations in other countries have never had the data tools to monitor local mercury emission hotspots before this report, Evers said. And even when hotspots are identified, it’s difficult to track what happens to the mercury after it’s emitted, with scientists having to account for local environmental receptivity and prevailing winds. 

“It really takes some thought and time to kind of work through all that,” Evers said.

Local experience seems to underscore Evers’ point. Two years ago, a Harvard School of Public Health study examined hair and blood samples for 172 people who lived near the Lafarge cement plant in Ravena, just across the Hudson River from northern Columbia County. Tests showed that 12 study participants had mercury blood levels so high that they should seek medical attention, according to published reports at the time. Although the cement factory is considered one of the larger in-state sources of airborne mercury, the Harvard study did not attempt to pinpoint the source of the mercury found in the blood of people living nearby.   

Less here, more there

Despite the difficultly of pinpointing the exact sources of mercury found in the environment, there is a growing awareness among regulators that the United States cannot act alone in curbing the effects of mercury in its own ecosystems, said Noelle Eckley Selin, an assistant professor of atmospheric chemistry at the Massachusetts Institute of Technology.

Since the 1990s, U.S. mercury emissions actually have decreased by 40 percent, thanks to new pollution controls and the growing popularity of natural gas. But the cuts in domestic mercury emissions haven’t lowered mercury content in U.S. waterways; that’s because of rapidly increasing mercury emissions in India and China, Selin said. If anything, global mercury emissions have remained more or less stable.  

“What’s happening is the decreases in the U.S. and Europe are compensating for the increases in China,” Selin said. “But it will start going up again.”

The EPA under the Obama administration has made a series of efforts to curb airborne mercury emissions, including a revised set of Mercury and Air Toxics Standards, finalized in March, for new power plants. This new set of rules is part of a package of changes that also will aim to curb emissions of greenhouse gases.

Regulatory changes at the EPA and trends in natural gas prices have already encouraged many utilities to take some coal-fired power plants offline, said Carol Oldham, the Northeast regional outreach coordinator for the National Wildlife Federation. And the new air emissions rules should make it even less likely that new coal plants will go online in the United States. 

“The carbon rule for new power plants means it would be difficult to build a coal-fired power plant,” Oldham said.

But the newest EPA rules actually do little to cut mercury emissions in the United States, argued Russell Bailey, an engineer at Trinity Consultants, an energy consulting firm. He said that’s because utility companies either already have installed pollution controls scrubbers or have taken old coal plants permanently offline, and they aren’t likely to build new coal-powered plants. For this reason, the EPA had to justify its new rules based on a cost-benefit analysis for controlling carbon, rather than for controlling mercury, Bailey said.

“If they tried to do a benefit for mercury, they really couldn’t justify it,” Bailey said.

Global treaty, local action

Evers said the increasingly global nature of mercury pollution requires a coordinated global effort to combat it. That’s why environmentalists hope a United Nations treaty, agreed to by 140 countries, will lower global mercury emissions in the next decade. The Minamata Convention on Mercury, which would put caps on coal-power mercury emissions and attempt to limit mercury use in gold mining, is not a new accord; it had been languishing on the table for a long time -- until shortly after President Obama’s election in 2008. 

“That’s when the U.S. came to the table to help facilitate the global mercury treaty which had been sitting there for years,” Evers said. 

The treaty still needs Senate ratification, but Evers said he believes it won’t receive significant opposition there because it sets global mercury standards that U.S. utilities already have met. By tightening limits for other countries, it creates a more level playing field, he said.

But even the treaty’s supporters concede that it will do little to cut mercury emissions until at least 2020, and local environmentalists don’t want to wait. 

Steven E. Letendre, a professor of economics and environmental studies at Green Mountain College in Poultney, Vt., said states like Vermont must do what they can now.

As director of the college’s renewable energy and ecological design program, Letendre has been part of a team helping the college to move away from non-renewable resources of energy. In recent years, he’s helped with projects to capture methane as a power source and to install a wood-burning boiler on the Poultney campus. 

Letendre says he realizes that global mercury emissions might continue to rise even if the college goes 100 percent green. He can understand those who question whether local efforts will make a difference in a world where new coal-fueled power plants go online every week in China or India. 

But the question doesn’t negate a need for action, he said. 

“That’s an issue of debate,” Letendre said.  “We have to start somewhere.”