Mercury has poisoned some of Lake Murray's most popular game fish for years, but the state's environmental department says the pollution hasn't been widespread enough to justify health warnings.
Unlike most major waterways from Columbia to the coast, Lake Murray does not carry a state health advisory against eating fish polluted by the toxic metal.
But recently released federal data show Lake Murray is among hundreds of reservoirs with fish that have exceeded a federal public health standard for mercury.
Nationally, nearly 49 percent of the 500 lakes tested contained fish with mercury in amounts above the recommended federal safety limit of 300 parts per billion, a Nov. 10 report said.
Lake Murray is one of those reservoirs, according to the U.S. Environmental Protection Agency.
The EPA, which produced the Nov. 10 report on contaminants in lake species, found that fish at Lake Murray registered 427 parts per billion. That's not only above the recommended federal health level but also a stricter state standard of 250 parts per billion.
While the data in the EPA study were collected nine years ago and only released last month as the nation's first baseline inventory of toxics in lake fish, state officials have been doing their own testing.
Those state test results, released recently by the S.C. Department of Health and Environmental Control, show mercury has continued to register each year of this decade in some species at Lake Murray. DHEC provided the data at the request of The State newspaper after the EPA released its report.
The state test results show about 40 percent of the lake's largemouth and striped bass tested from 2000 to 2008 had mercury levels above South Carolina's health safety limit, according to the newspaper's analysis.
DHEC's records also show that 35 of 43 fish found to have unsafe mercury levels were either largemouth bass or stripers, popular gamefish that people also like to eat.
Agency officials say people should not be overly concerned because higher mercury levels can be expected from time to time in some fish. But they say high mercury readings since 2000 in certain species have been sporadic and not consistent enough to justify warning the public.
Overall, the lake's fish are free of dangerous mercury levels, the agency maintains. DHEC tests a variety of fish, not just bass, and records show many of those are free of high mercury levels.
"Mercury has been consistently low in the many fish species that have been tested by DHEC," the agency said in a written response Friday to The State newspaper.
Finding mercury in any Lake Murray game species might shock some people.
Long known for its clear, sparkling water, the lake is arguably the Midlands top recreational attraction. On summer weekends, the 50,000-acre lake is full of boaters, water-skiers and swimmers. The lake also is home to thousands of residents and regularly attracts bass fishing tournaments. In 2008, the lake hosted the Forrest Wood Cup, one of professional bass fishing's richest tournaments.
Lake resident Bob Keener, who has been active in water protection efforts for years, said it's unnerving to think some fish have mercury levels above safety standards.
"It should be a concern to anybody," Keener said. "If the level is high enough, this can be detrimental to your health. This is such a beautiful, wonderful lake, to think there is anything that detracts from its benefits is disconcerting."
Other leaders of shoreline community groups said the levels could be a warning of things to come. Some fishermen said more study is needed.
"It's a cause of concern, but we need to learn if it's a consistent problem," veteran bass angler Rick Kellemeyer of Chapin said. "I don't know if I'll be doing anything different."
Mercury is a threat to people who regularly eat tainted fish because it can cause brain damage, kidney problems and nervous system disorders in those exposed to elevated levels. High levels in the bloodstream of unborn babies and young children may harm the developing nervous system - which makes the child less able to learn, according to the EPA's Website.
One retired state fish biologist said he wouldn't eat any largemouth bass from Lake Murray - even if DHEC hasn't issued an advisory. Most large, long-lived predators, such as bass, accumulate enough mercury to make them unsafe to eat, said Charlie Moore, who studied the mercury problem at the S.C. Department of Natural Resources for part of 28 years.
"In the Southeast, any largemouth bass that is over a 3- to 4-pound fish is going to test over the limit," Moore said, noting that "I would not eat largemouth bass from freshwater in the Southeast."
The heavy metal is a problem in fish nationally, but of particular concern in the South because the chemistry of many rivers and lakes can easily convert one form of mercury into the more dangerous methylmercury. The mercury comes mostly from air pollution, particularly released at coal-fired power plants. The air pollution rains back to earth and settles in rivers or lakes.
Fish then take in the mercury-tinged water, and predator fish eat other species also exposed to the mercury. Over time, mercury builds up in the flesh of the oldest and largest predator fish. Mercury in fish depends on what they eat, how long they live and how high they are in the food chain.
Moore said many species of fish are virtually mercury free and safe to eat in South Carolina, but he said DHEC should consider issuing statewide blanket warnings against eating certain top predators, such as largemouth bass.
About three dozen states, including North Carolina, have blanket advisories against eating some species, no matter what river or lake the fish come from. North Carolina's advisory tells the average person not to eat more than one meal per week of largemouth bass anywhere in the state.
In South Carolina, the state issues advisories for individual waterways. All told, DHEC has issued more than 60, mostly in the coastal plain, but also some in the Upstate.
The EPA report that found high mercury levels at Lake Murray is significant because it shows the most common pollutants in lake fish across the country. Mercury and PCBs, which can cause cancer, were the top two pollutants.
Federal officials say the report gives a snapshot of contaminant levels at the 500 lakes tested, but they say the testing was limited and it is up to states to decide whether to issue mercury advisories. The report was only issued recently because it took so long to compile and analyze data, the EPA said.
DHEC's testing from 2000 to 2008 at Lake Murray showed at least 43 fish with mercury levels above the state safety standard of 250 parts per billion, according to agency data.
That's about 20 percent of the total fish tests from 2000 to 2008, but some species - primarily bass - were far more likely than others to register elevated mercury levels, according to DHEC data analyzed by The State.
State regulators did not release a breakdown of mercury testing data for 2009. Agency data collected from 2000 to 2008 by DHEC show that:
- 38 percent of the largemouth bass DHEC tested had elevated mercury levels. Twenty-nine of 75 fish tests were above the state safety standard.
- 55 percent of the striped bass the agency tested showed elevated mercury levels. Six of 11 tests by DHEC revealed levels above the state safety standard.
- 26 percent of the chain pickerel tested showed elevated mercury levels. Five of 19 fish tests were above the state safety standards.
Other Lake Murray species fared better. None of the bluegill or redear sunfish showed mercury contamination above safe levels, DHEC's data show.
Jim Glover, who manages the aquatic biology division at DHEC, said the higher levels noted in DHEC's records represent one-time tests.
DHEC uses a rolling three-year average for mercury in deciding whether to issue health warnings for certain species on different waterways. At Lake Murray, the average has never been high enough over any three-year period to issue warnings, agency officials said.
"Most authorities agree that you have to have multiple data points" or consistently high levels, Glover said. "You would not go out and just take a single data point."
Glover said some of the fish tested for the EPA's study in October 2000 were taken not far from the Saluda River as it flows into Lake Murray in Newberry County. The Saluda River above Lake Murray already carries health advisories against eating more than moderate amounts of largemouth bass, bluegill and mudfish.
"You've got to remember that Lake Murray is the Saluda River that has been dammed," Glover said. "If you come far enough up, it stops becoming a lake and starts becoming the Saluda River."
DHEC's tests show roughly the same number of elevated mercury levels in bass at both its upper lake monitoring station and the station near the dam on the lower lake.
Glover also said that mercury levels in fish are dropping across South Carolina, but he did not elaborate.
Statewide, DHEC has issued health warnings against eating certain species in many of the state's most popular recreational lakes, such as Marion, Moultrie, Russell, Jocassee and Thurmond. At Lake Marion southeast of Columbia, for instance, people are advised not to eat more than one meal of largemouth bass per week. The slower-moving rivers of the Pee Dee, between the Midlands and the coast, have had the most trouble with mercury.
Lake Murray resident Keener said he thinks his reservoir is likely affected by the same airborne pollution other rivers and lakes in South Carolina face: contamination from coal-fired power plants. Power company SCE&G has a small coal-fired power plant near the Lake Murray dam, but Keener noted that the state has many coal plants used to generate electricity.
"That's why the whole country is having a degree of contamination from mercury - coal has been so widespread," he said.