Levels of 1,4-Dioxane in finished, or treated, drinking water in Pittsboro are below the EPA and North Carolina’s drinking water health advisory level, but much higher than stricter advisory goals for surface water.
The Town of Pittsboro released the results today, based on sampling from July 1 through July 6, shortly after Greensboro illegally discharged the toxic compound from its TZ Osborne wastewater treatment plant on June 30. The source of the 1,4-Dioxane has not been publicly disclosed, but state documents show that the City of Greensboro has required additional sampling from one of its industrial customers, Shamrock Environmental.
Treated drinking water levels in Pittsboro ranged from 1.06 parts per billion to 5.56 ppb. The highest level was detected on July 6 at the Chatham Forest tank.
The EPA health advisory goal for 1,4-Dioxane in drinking water is 35 ppb, which represents a 1 in 10,000 lifetime excess cancer risk.
The drinking water goal is controversial because the EPA recommendation for 1,4-Dioxane in surface water is more stringent — 0.35 parts per billion. That represents a
1 in 1 million lifetime excess cancer risk for humans, which the scientific community considers “acceptable.”
If the EPA and North Carolina’s drinking water recommendation for 1,4-Dioxane were as rigorous as that of the surface water, Pittsboro’s levels would be three to 15 times above the guidelines.
Six states have enacted stricter guidelines for 1,4-Dioxane in drinking water than North Carolina, all of them below 1 ppb: Colorado, California, Massachusetts, New Hampshire, New Jersey and Washington.
The raw water taken from the intake along the Haw River showed that on July 1, levels of 1,4-Dioxane were not detected. But on July 2, two days after the Greensboro release, concentrations in the Haw River hit 76.5 parts per billion. Levels decreased to 2.46 ppb on July 3, possibly because it had rained, before rebounding to 43.7 ppb by July 5.
These concentrations are seven to 200 times the EPA guidelines for surface water.
Pittsboro town staff will continue sampling until the results show non-detections “for an extended period,” according to a press release from Town Manager Chris Kennedy.
1,4-dioxane is toxic to people, causing liver and kidney damage, and increases the risk of cancer. It is used, and created as a byproduct, when manufacturing chemicals, paints, cosmetics, cleaning products, dyes, textiles, paper, and other products.
Below is a screenshot of the press release with the results and sampling points.