Hoosier Streams Still Have High Mercury Levels

Hoosier Streams Still Have High Mercury Levels
Indianapolis Star (2/2/2009)
Shari Rudavsky

Levels of mercury remain high in several Indiana streams and rivers, despite years of effort to reduce the contaminant, which can cause neurological damage.

More than 80 percent of samples taken from Indiana streams from 2004 to 2006 contained detectable levels of mercury, according to a U.S. Geological Survey study. Preliminary analyses on data collected in 2007 and 2008 indicate that not much has changed.

The 2004-06 study also found that 10 out of the 25 streams monitored had at least one reading that exceeded the safe level for mercury, and about 6 percent of more than 200 samples contained enough mercury to harm humans. Analysis of the 2007-08 data is still under way.

People and wildlife consume mercury through contaminated fish. The amount of fish that can be safely eaten depends on the size, the species and the stream in which it is caught.

For instance, people are advised to eat no more than one meal a month of flathead catfish caught in the West Fork of White River downstream of the Broad Ripple Dam. Pregnant or breastfeeding women and children younger than 15 are advised not to eat any of the fish.

"It's a very complicated story that we're trying to unravel here, and there are a lot of different things that play into it," said David Gay, coordinator for the Mercury Deposition Network, a national consortium of scientists tracking mercury in rain.

State and federal efforts to decrease mercury in streams have focused on reducing emissions from power plants. But recent USGS studies suggest that strategy hasn't had a significant impact.

While many of the state's regulatory efforts have focused on local emissions into the air, contamination could be coming from many sources, said Dan Murray, the Indiana Department of Environmental Management's assistant commissioner for the office of air quality.

Mercury can stay in the atmosphere for up to a year and travel thousands of miles. Eventually, the USGS study may shed light on where Indiana's mercury originates, IDEM officials say.

"We're trying to understand the amount that's being deposited and where it may be coming from," Murray said.

Mercury emissions in Indiana's air decreased by 28 percent from 2002 to 2005. However, the amount of mercury detected in precipitation decreased by only 3 percent, according to the USGS.

"It's not a real dramatic percentage by anybody's rating, and we're not really seeing . . . change in the streams," said Martin Risch, a USGS scientist who studied the issue.

Conducted in conjunction with IDEM, the USGS studies aim to gather information on how Indiana is faring over time. Few other states have projects under way to study mercury over time.

The study serves as "a tool to help us understand what sort of reality we face in Indiana and what kinds of things we need to do more of to address the mercury issue," said Bruno Pigott, assistant commissioner for the office of water quality at IDEM. "It raises questions and helps us move forward."

Risch and colleagues spend about an hour every week at each of five rain stations around the state. Four times a year, they sample water from 25 streams statewide.

Mercury can also leach into streams through industrial wastewater. Automotive switches, dental fillings, thermometers and other medical waste can contribute, if they are not disposed of properly.

IDEM limits the amount of mercury that wastewater treatment plants can release, and the agency also provides guidance on how households and commercial users can limit mercury emissions.

Environmental activists around the state said they did not find the USGS findings surprising.

Water tested at Clifty Falls, a recreational site near Madison, had levels of mercury that were among the highest of any precipitation collection in the nation.

Richard Hill, president of Save the Valley, an environmental group in southeastern Indiana and northern Kentucky, noted that the site sits close to a number of power plants and is downstream from an older plant.

"I think it's just more than a coincidence that the higher levels are here," he said. "It just makes sense that such a big polluter that is based here has readings that high close to it."

Some state environmentalists believe that the USGS study failed to include the region most affected by mercury.

Power plants in southwestern Indiana emit more mercury than most others, but there is no testing site for precipitation there, said John Blair, president of Valley Watch, based in Evansville.

"They didn't want to have true data from the area that truly is the largest concentration of coal-fired power plants in the world," he said.

Scientists have no answer on when, if ever, a decrease in mercury emissions will translate into a decrease in mercury in streams.

Some scientists believe that one eventually will follow the other, Risch said. While some say that will take less than 10 years, others are not so sure.

"That time lag is uncertain because it's going to vary from place to place," he said.

Blaming mercury in streams on power plant emissions alone misses the big picture, said Hill, whose group advocates for a range of solutions, including energy alternatives.

"One of the main things to consider is not to get into a real bad argument about where it's coming from, because you can't show that," Hill said. "It's an overall effect that needs some overall action."

Call Star reporter Shari Rudavsky at (317) 444-6354.