• Elemental (metallic) mercury and all of its compounds are toxic, and exposure to excessive levels can permanently damage or fatally injure the brain and kidneys.
• For children, infants and fetuses, the primary health effects of mercury involve neurological development. Impacts on memory, attention, language and other skills have been found in children exposed to moderate levels in the womb.
• Elemental mercury can also be absorbed through the skin and cause allergic reactions.
• Ingestion of inorganic mercury compounds can cause severe renal and gastrointestinal damage.
• Organic compounds of mercury such as methyl mercury are considered the most toxic forms of the element, and exposures to very small amounts of these compounds can result in devastating neurological damage and death.
Source: National Institutes of Health
Raw water at the Eastside Utility District in Tyner and the Tennessee American Water Plant in Chattanooga is being checked three times a day for mercury contamination, according to state environmental regulators.
Olin Corp. spokeswoman Elaine Patterson and regulators said Tropical Storm Lee's 12.7-inch record-breaking rainfall filled the Charleston chlorine plant's discharge treatment lagoon in Bradley County until it reached a point of overflow.
About 50 pounds of mercury spilled into the Hiwassee River over the past three days, according to Tisha Calabrese-Benton, spokeswoman for the Tennessee Department of Environment and Conservation.
Normally Olin is permitted to release on 70 pounds of mercury in a year, she said.
The Hiwassee drains to the Tennessee River.
Patterson said Olin workers have shut down plant production and are working hard to reduce the discharge.
"We are implementing a TDEC-approved plan that will allow us to meet daily permitted levels as soon as possible," Patterson said.
Calabrese-Benton said first water utility test samples -- taken Thursday and analyzed Friday on water from Eastside's and Tennessee American's raw water intakes and finished water, show "everything at this point meets drinking water standards for mercury."
But Calabrese-Benton said it could take several days for the mercury to be carried in the rivers for 42 miles to the first intake: Eastside.
Olin, a caustic soda and chlorine manufacturing plant, is one four chlorine makers in the U.S. that still uses mercury in its production process. Plant operators have said they will phase out the use of mercury in the plant next year.
Patterson said Olin's staff notified the National Response Center and state regulators as soon as they realized the lagoon was flooding.
"Although the plant had made extensive preparations for increased rainfall, the water treatment system at the plant could not support the record-breaking volumes of rainfall," she said.
Precautions and remedies
TDEC officials said carbon filtration can remove mercury from water.
Tennessee American has that technology, but Eastside does not, according to TDEC spokeswoman Meg Lockhart.
But Lockhart said water experts say mercury in raw river water "should not make it past flocculation and sedimentation processes" at a water treatment plant because mercury is heavier than water and it should sink.
Flocculation is the separation of particles in suspension from a liquid.
Sedimentation is the settling out and sinking of the particles.
Tennessee American supplies water to about 400,000 residents in the Chattanooga area and North Georgia. The water company couldn't be reached for comment. A call to the company's emergency customer number also did not prompt a response.
Eastside supplies about 20,000 customers, and Don Stafford, who heads the utility, said he is not concerned about the mercury threat.
"I don't think it will ever reach us," Stafford said. "A boat can't float down here in three days."
Stafford said Eastside officials are in contact with Olin and TDEC.
"We're on top of everything," he said.
Calabrese-Benton said it's too soon to know if Olin will face state sanctions.
"It is a violation of their permit, but it also was due to a severe weather event. The first order of business is for them to get the treatment at the [lagoon] working," she said. At the moment the lagoon is still too flooded.
Tennessee Wildlife Resources Agency biologist Bobby Brown said time will tell how TWRA will react.
"If we start seeing fish popping up dead, we'll get more involved," he said, noting that for now TDEC is taking charge in the oversight of the spill monitoring and remedy.
Mercury often accumulates in sediments and is eaten by aquatic bottom feeders. Because it doesn't biodegrade, over time the toxic element accumulates up the food chain as larger fish and animals eat the smaller ones.
Already much of lower section of the Hiwassee River is posted with warnings about eating mercury contaminated fish caught there.
Eating fish with elevated levels of mercury puts people at risk for mercury poisoning and neurological problems, according to health and environmental officials.