Duke University researchers say they’ve found relatives of the chemical GenX in Jordan Lake, two of its feeder streams and in the town of Cary’s tap water.
The discovery, from Nicholas School of the Environment professors Heather Stapleton and Lee Ferguson, surfaced Thursday in a report by the interest group N.C. Policy Watch. Stapleton elaborated in an interview with The Herald-Sun, and supplied a map showing a colleague had drawn the feeder-stream samples from Northeast Creek in south Durham and Morgan Creek downstream of Chapel Hill.
Those samples, and a third drawn near Cary’s Jordan Lake water intake, all returned detectable levels of nine “perflorinated chemicals” that have been in use longer than GenX, Stapleton said, adding that she subsequently alerted Cary water-system officials and shared the data with them.
Cary officials responded by ordering some tests of their own, which likewise found small amounts of at least a few of the chemicals in their system’s water intake, treatment filters and tap water. But town spokeswoman Susan Moran said the findings suggest the two key contaminants aren’t present at levels the U.S. Environmental Protection Agency thinks are anything to worry about.
“We continue to meet or exceed all standards, and our water is safe,” she said, adding that Cary officials are “coordinating” with state regulators and the Duke scientists.
Stapleton indicated the discovery was happenstance, growing out of her efforts to help a group in Duke’s medical system unravel the mystery of why people in a community in Robeson County, in the southeast part of the state, suffer an unusual number of chronic kidney problems.
She decided to check its water and look among other things for GenX, the chemical that’s sparked controversy and worry since officials found out a factory near Fayetteville had spilled it into the Cape Fear River.
For the ensuing lab work, Stapleton needed a “control sample” to compare the Robeson water to. She decided to use tap water from her own house in Cary, and got a surprise.
“It turns out I found nothing in Robeson County and these chemicals in my own drinking water, at levels that seemed high to me,” she said, stressing that the testing “did not find” GenX itself anywhere she and her collaborators looked.
The next step was to have another lab re-run the tests, to verify them. That done, at the end of October a colleague pulled the samples from Jordan Lake and its feeder streams.
“That third analysis showed us the levels in the finished water were very similar to what’s in Lake Jordan,” Stapleton said. “We know these chemicals are not removed efficiently in drinking-water treatment.”
The map of the sampling sites showed that the Morgan Creek sample came from where the stream flows under Farrington Mill Road. The Northeast Creek sample came from a point near the stream’s passage under Grandale Drive, about 1,000 feet south of Grandale’s intersection with Scott King Road.
Sewage treatment plants
Stapleton thinks it’s unlikely the chemicals are “industrial effluent.” But she does suspect they come from a sewage treatment plant, and as it happens, both creeks receive treated waste from such facilities.
The Morgan Creek sampling point is roughly 2 1/2 miles below the Orange Water and Sewer Authority’s sewage plant, and the Northeast Creek one is close to where Durham County’s Triangle Wastewater Treatment Plant discharges effluent. The Durham County plant receives sewage from a portion of south Durham, but exists primarily to serve RTP because the law forbids the city of Durham from annexing the industrial land there.
Thursday’s report was news to Durham County Manager Wendell Davis, who said he’d refer it to aides who operate the Triangle plant. Officials will examine the testing “at that point and go from there,” he said.
Stapleton said the chemicals involved that have attracted the most regulatory and scientific interest are called perfluorooctane sulfonate and perfluorooctanoic acid, more commonly referred to as PFOS and PFOA, respectively. They’ve been used, like GenX, in non-stick coatings and also have figured in stain-prevention treatments.
An acting deputy director in the Durham County’s engineering department, Stephanie Brixley, later said county officials “are unaware of any users” that are discharging either chemical to the Triangle plant. “We do not have any sampling data for these pollutants on the effluent,” she added.
OWASA’s sustainability manager, Mary Tiger, said the Carrboro-based utility “definitely” wants to hear from the Duke researchers.
Tiger added that OWASA is “not testing for these compounds in the effluent, in the discharge from our wastewater treatment plant.”
She further said there are “no major industries” in OWASA’s Chapel Hill and Carrboro service area. But that comment overlooked that by definition the plant receives waste from UNC-Chapel Hill, which hosts a large variety of scientific and medical research labs.
PFOS and PFOA are the subject of a non-binding health advisory from the EPA that urges water departments to notify state regulators and residents if they’re found in concentrations above 70 parts per trillion – an amount Cary officials reckon is equivalent to about 70 drops of water in 10 million gallons. The EPA gears advisories to the needs of what it calls “the most sensitive populations,” namely “fetuses during pregnancy and breast-fed infants.”
Another EPA document noted that the two man-made chemicals have been found in surface water, sediments and sewage effluent elsewhere in the U.S., and can show up in unexpected places like the Arctic. They’re “extremely persistent” once they’ve been released, the document said.
One of Cary’s tests found 15 parts per trillion in of PFOA in its Jordan Lake water intake and 11 parts per trillion of PFOS there. By the end of the treatment process, that was down to 9.6 and 4.0 parts per trillion, respectively. Those levels declined only slightly before reaching the tap at two testing sites.
Stapleton noted that the EPA guideline isn’t as tough as those some states have issued. New Jersey regulators, worried about the chemicals’ effects on human development and links to other health problems, watch for concentrations of PFOA as small as 14 parts per trillion. Vermont looks out for PFOS concentrations larger than 20 parts per trillion.
The other seven chemicals the Duke professors found haven’t attracted as much research interest over the years and “we don’t know if they’re better or worse in their toxicity,” Stapleton said, adding that adding up the concentrations of all nine chemicals in the lake and stream samples yielded totals ranging from 115 to 277 parts per trillion.
Jordan Lake is Cary’s primary drinking water supply, but for now is only a backup source for the Durham city and OWASA systems. Both have their own, separate reservoirs that normally supply their communities’ daily water needs.