DHEC: No mercury warnings for Lake Murray

The state health department doesn’t plan to warn people against eating mercury-tainted fish caught at Lake Murray because agency officials say the fish don’t contain enough of the pollutant to threaten public health.

While the toxic metal has shown up in bass for at least a decade in the popular lake, a top state water quality official dismissed a report Wednesday that his agency was preparing to issue warnings.

“I don’t see us listing Lake Murray, that’s not what our data show,’’ said Jim Glover, who manages the aquatic biology section at the S.C. Department of Health and Environmental Control.

Lake Murray is one of the few major water bodies from the Midlands to the coast that does not carry an advisory against eating more than moderate amounts of some fish species. Some critics say that because mercury is so pervasive in the environment, DHEC should consider health advisories on big bass in every river and lake that does not carry a warning.

An expansive waterway that touches four counties, Lake Murray is the Columbia area’s top recreational lake. On a typical summer day, it is filled with boaters, skiers and anglers, and has been home to major national fishing tournaments. Thousands of people live along the lake’s shores.

People who regularly eat fish contaminated with elevated amounts of mercury can develop health problems over time. Among other things, mercury can cause brain damage and kidney system disorders. It is particularly toxic to developing fetuses and young children, whose ability to learn can be limited by chronic mercury exposure.

The question of whether to issue warnings at Lake Murray surfaced during a mercury discussion at a Clemson University water conference in Columbia. A conference participant said he had heard warnings were pending. But Glover said the amounts in Lake Murray fish remain below the limit the agency uses in deciding whether to issue warnings.

Glover said DHEC is finding some fish with mercury levels of .22 parts per million; the DHEC standard is .25 parts per million, or 250 parts per billion.

But a 2009 federal report and DHEC records show that some largemouth and striped bass in the lake contain elevated levels of mercury. Records reviewed by The State last year show that about 40 percent of the bass tested from 2000 to 2008 contained levels above South Carolina’s safety limit.

DHEC has not disputed that. But the agency typically relies on a three-year average of elevated mercury levels before considering warnings — and officials say that hasn’t happened.

Glover suggested mercury in Lake Murray fish has been influenced, in part, by decisions to raise and lower the lake’s water level for various reasons the past decade, a factor that sometimes can increase mercury. The lake provides hydroelectric power and is operated by SCE&G.

Mercury pollution in fish is a national problem that is of particular concern in the Southeast. Industrial plants, medical waste incinerators and coal-fired power stations are major sources of mercury pollution to the air. Once released, mercury falls back to earth, often in raindrops, and settles into waterways. Over time, the material builds up in fish that are constantly exposed to mercury, making some species unsafe to eat. Large predatory fish, such as bass, are most likely to contain high mercury levels.

South Carolina has been shown to have some of the highest mercury levels in fish of any state in the country, said Paul Bradley, a researcher with the U.S. Geological Survey. That’s more of a problem in the coastal plain, scientists suspect, because the region has so many more wetlands than the Upstate. Wetlands tend to help convert mercury that rains to earth into methyl mercury, the form of concern in fish.

The Upstate has only 1 to 2 percent wetlands, compared to about 15 to 20 percent in the coastal plain, Bradley said.

Although the Congaree River system contains elevated mercury in fish, Bradley said the influence of Piedmont flooding on the Congaree River system may keep the mercury levels lower than in the Edisto basin. The Edisto River is not influenced by the Piedmont and has significantly higher mercury levels in fish.

Mercury is more of a problem in the Southeast because the region has so much more precipitation than western states, according to data presented at Wednesday’s conference by Dennis Jackson, a researcher with the Savannah River National Laboratory. Jackson said the Savannah River, for instance, gets about 45 inches of rainfall per year. Western states routinely get only a fraction of that.