Legislators probed a question Wednesday that has bedeviled regulators and hundreds of North Carolina households: How can contaminants that are deemed safe in public water systems be labeled risky in private wells?
The state Health Department last spring advised more than 400 well owners, neighbors of Duke Energy power plants, not to drink their water. Most warnings cited detections of two substances that might come from Duke’s coal ash ponds.
But similar levels of the contaminants, hexavalent chromium and vanadium, also appear in the municipal water of Charlotte, other North Carolina cities and across the United States. That water is judged safe to drink under federal standards.
“We’re telling people that their water is unsafe, and now we’re telling them that maybe it might not be,” Sen. Andrew Brock, R-Mocksville, said as the Environmental Review Commission met Wednesday. “Nothing gets more personal than messing with somebody’s water.”
The state’s environment and health agencies sparred for months, internal records show, over how to assess contaminants in private wells in the absence of relevant standards.
Officials worried most about hexavalent chromium, a form of the metal that may cause cancer in people who drink tainted water. Hexavalent chromium figured in “Erin Brockovich,” the 2000 movie based on real-life groundwater contamination in California.
Research and the understanding of acceptable levels of toxic substances in the environment is evolving.
In 2008, the Environmental Protection Agency began considering whether to set limits on hexavalent chromium. The EPA has called it likely to cause cancer in humans if ingested in drinking water because of tumors found in rats and mice, and because of some evidence of stomach cancers in humans.
But North Carolina, like the federal government, has set no limit on how much hexavalent chromium in drinking water is safe.
In North Carolina, as officials prepared to test nearly 500 wells near Duke’s power plants, they needed a benchmark by which to compare results. The Department of Health and Human Services used its own calculations: the level that might cause one cancer in 1 million people over a lifetime of exposure.
Department of Environmental Quality officials expressed alarm that the newly calculated screening level for hexavalent chromium in wells, 0.07 parts per billion, was too tough. Public water systems have only to meet a far higher federal standard for total chromium of 100 ppb, which includes hexavalent chromium.
Conflicting standards, DEQ argued, would mislead the public.
“Directing people to undertake certain mitigating activities with perhaps negligible health benefit is very different than alerting them to their risk in an understandable way,” Jessica Godreau, chief of the state’s public water supply section, wrote another DEQ official last March.
DEQ eventually consented to the tougher standard. While 424 of 476 well owners got don’t-drink advisories, only 12 wells broke federal water standards.
Nearly a year later, Assistant Environment Secretary Tom Reeder told the commission, “It’s incredibly confusing to the consumer.”
“Decide which agency is in charge,” said Sen. Ronald Rabin, a Harnett County Republican. “It can’t be two different agencies in charge of water or it’s chaos.”
Municipal, private water
Health officials say they followed protocol in developing the screening levels on which their recommendations were based.
“One reason it’s complex is that we have municipal water, groundwater, new wells and old wells. You’ll hear different (standards) for all those things,” said Dr. Randall Williams, deputy secretary of health services. “We’re aware that different agencies and different parts of the government look at each of these four entities in different ways.”
While public systems have to comply with federal standards, private well owners are essentially on their own to ensure their water is safe. The state investigation of Duke’s groundwater contamination followed a 2014 ash spill into the Dan River and state legislation that ordered a broader look at ash issues.
The health agency will reassess its recommendations when more groundwater test data are reported in the next month, he said.
Amy Brown, a neighbor of Duke’s Allen plant in Gaston County, said she appreciated Williams’ personal visit after Christmas. But after eight months on bottled water, she added, her neighborhood is “in limbo. We have no real answer. We can’t sell our houses. And we didn’t ask for this, not one bit of it.”
Duke says groundwater data indicate the well contaminants come from natural sources, not ash ponds.
Similar levels of hexavalent chromium and vanadium occur in soil and rock miles from ash ponds, Duke says. With one exception, it says, the boron that serves as an indicator of ash has not been found in private wells.
“We strongly agree that clarity is needed on state drinking water standards so plant neighbors and others across the state who have been told not to drink their water get this issue resolved soon,” spokeswoman Erin Culbert said by email.
Hexavalent chromium is used to make stainless steel and tan leather and to preserve wood. Pacific Gas & Electric, which settled a class-action lawsuit over groundwater contamination in California, used it to reduce corrosion at a power plant.
North Carolina officials, in calculating a screening level for the substance, relied on California’s work with hexavalent chromium.
In 2011, California set the nation’s first “public health goal” for hexavalent chromium in drinking water: 0.02 ppb, even lower than North Carolina’s screening level. A public health goal is not an enforceable standard but represents the level that does not pose a significant health risk.
But in setting a regulatory standard in 2014, California set a much higher bar of 10 ppb after weighing the technical feasibility of detecting the contaminant at low levels and treatment costs.
Jacqueline MacDonald Gibson, who specializes in risk assessment at UNC Gillings School of Global Public Health, said North Carolina’s screening level is “extremely, extremely, extremely conservative.” Among other assumptions, she said, it makes the leap that humans will develop tumors as rats did.
“It’s kind of unfair to ask homeowners to answer what does 1 in a million mean,” she said. “If it were just me, it’s a judgment call,. But if it were my well and the standard is much below what California says is acceptable, I would go ahead and drink the water.”
Whether the level is too conservative, she added, is for policymakers to decide.