Shamrock Environmental Corporation is the source of a recent 1,4-Dioxane release into the Greensboro wastewater treatment plant, the North Carolina Department of Environmental Quality announced today.

DEQ is investigating the discharge, which occurred in August but was not reported by the City of Greensboro until Sept. 27. Although the 1,4-Dioxane, a likely carcinogen, originated with Shamrock, the discharge permit for the pretreatment program is held by the city, DEQ said.

North Carolina Health News reported several weeks ago that there had been a spike in 1,4-Dioxane levels downstream in the Pittsboro drinking water supply — the Haw River. This week, Greensboro officials and DEQ declined to name the company to NC Health News.

City officials are cooperating with the investigation, DEQ said. As a result, DEQ has initiated weekly sampling for 1,4 dioxane at Greensboro’s wastewater treatment plant.

1,4-Dioxane is not regulated by the EPA. It is persistent in the environment and impossible to remove using traditional water treatment methods.

Shamrock is headquartered in Browns Summit; it has several facilities in North Carolina and one in Virginia. The Patton Avenue plant, responsible for the discharge, is a tanker cleaning facility. It also treats and manages wastewater, recycles and disposes of drilling mud, and hauls waste.

DEQ’s online waste management document site does not list any notices of violation; nor does the Division of Water Resources online records repository. However, neither is comprehensive.

1,4 dioxane has historically been used as a solvent stabilizer and is currently used for a wide variety of industrial and manufacturing purposes. The compound can be found in industrial solvents, paint strippers, and varnishes and is often produced as a by-product of chemical processes to manufacture soaps, plastics, and other consumer products.

It’s often a byproduct of plastics manufacturing. Earlier this year, a Policy Watch investigation found that very high levels of 1,4-Dioxane in wastewater sludge from DAK Americas, a plastics plant in Fayetteville along the Cape Fear River. The facility was shipping its sludge to McGill Environmental, which was using it to make compost. Although the finished compost didn’t contain 1,4-Dioxane — it likely had evaporated — it was contaminated with PFAS, also known to be in wastewater sludge.