Levels of 1,4-Dioxane, a likely carcinogen, have increased in Pittsboro’s drinking water over the past week, as an illegal discharge makes its way downstream, according to town officials.
The release came from Greensboro’s TZ Osborne wastewater treatment plant on April 5. The plant discharges into South Buffalo Creek, a tributary of the Haw River, which is Pittsboro’s drinking water supply. Lanxess, an international chemical company with a plant in south Greensboro, discharges into the Patton trunk line, one of several that feed the wastewater treatment plant. Lanxess informed the city that self-monitoring showed it’s the source of the 1,4-Dioxane, according to a press release.
A day after the release, on April 6, levels of 1,4-Dioxane in Pittsboro’s finished drinking water — which has been treated — were 5.12 parts per billion. On April 8, the levels had more than doubled, to 11.9 parts per billion. Traditional drinking water treatment systems don’t remove the compound, according to Town Manager Chris Kennedy. Additional sampling is ongoing, he said.
The EPA does not regulate 1,4-Dioxane in drinking water. The agency has set a health advisory goal of 35 ppb, which is equivalent to a 1-in-10,000 additional cancer risk over a lifetime. In surface water the rules are stricter: 0.35 ppb, is the legally binding standard. It represents a 1-in-1 million additional cancer risk. The compound has several industrial uses, including as a degreaser, and can be a byproduct of plastics manufacturing.
Preliminary levels of toxic 1,4-Dioxane were reported at 52 parts per billion in Greensboro’s wastewater. Further testing on April 5 and 6 showed lower levels, ranging from 22.1 ppb to 37.9 ppb.
A consent order and settlement agreement among Greensboro, state regulators, Haw River Assembly and Fayetteville Public Works Commission caps the amount of 1,4-Dioxane that can be released at 35 ppb. Starting May 1, the threshold decreases to 31 ppb.
Greensboro has installed monitoring stations on trunk lines within its citywide sewer system. Surveillance data shows the Patton trunkline measured 1,4-Dioxane at 95 ppb. Lanxess discharges into that trunkline.
However, additional data shows even higher levels of the compound — 599 ppb — entered the Bryan Park trunkline between April 1 and 4. That trunkline is south of Shamrock Environmental, in Browns Summit. That company was responsible for a previous discharge in 2019 that also contaminated Pittsboro’s drinking water. The source of two other 1,4-Dioxane releases last year have not been identified.
This story has been corrected to reflect the legally binding standard of 1,4-Dioxane in surface water.