Despite upstream spike, local levels of 1,4-dioxane below immediately available detection

NEW HANOVER COUNTY ––– Recent test results of 1,4-dioxane in the raw and finished drinking water supply for about 80% of public customers in New Hanover County show the likely carcinogen is below immediately available detection levels. 

Cape Fear Public Utility Authority requested expedited lab results from a consultant –– which typically takes two weeks to produce results –– after being informed of an upstream spike in the compound, first detected June 30 in Greensboro. 

RELATED: GenX got attention. Progress on 1,4-Dioxane has lagged behind


With the lengthier turnaround, the lab can detect 1,4-dioxane at levels as low as 0.07 parts per billion (ppb); in the latest round of expedited testing, the threshold was higher, with detection reported as low as 2 ppb. 

The industrial solvent has been observed in alarming levels upstream on the Cape Fear River in recent years, notably in Pittsboro and Greensboro. Despite maintaining an internal log of 1,4-dioxane dischargers, the N.C. Department of Environmental Quality long safeguarded the companies’ identities. The department only caved in revealing one company in 2019 by releasing Pittsboro’s source of 1,4-dioxane (Shamrock Environmental Corp.) –– responsible for an accidental spike in drinking water levels to 300 times the Environmental Protection Agency’s lifetime cancer risk threshold –– the day after N.C. Health News published an article with a headline stating the regulators wouldn’t reveal the company’s identity. 

1,4-dioxane is not regulated by the Environmental Protection Agency. The Environmental Protection Agency and the Department of Environmental Quality have cited a non-enforceable drinking water health advisory of a maximum of 35 ppb for the compound, representing a lifetime exposure cancer risk threshold of one in 10,000, based on the EPA’s findings. (The EPA’s initial one-in-1,000,000 risk standard of 0.35 ppb was established in 2010; in 2018, its updated recommendations were more relaxed, at 35 ppb at a one-in-10,000 cancer risk level.)

CFPUA’s Sweeney Water Treatment Plant is currently equipped to filter out about two-thirds of 1,4-dioxane present in raw water through the process of ozonation and the use of biological filters. The authority’s removal rate of 1,4-dioxane will not improve with the onset of new granular activated carbon filters, as part of its $215 million overhaul to enhance per- and polyfluoroalkyl substances (PFAS) removal efforts –– a response to the contamination crisis triggered by Chemours in Fayetteville. 

1,4-dioxane was observed as high as 1.3 ppb in finished CFPUA drinking water in September 2019, 3.7 times higher than the EPA’s one-in-1,000,000 threshold.

The latest 1,4-dioxane results show the compound measured at 0.46 ppb in finished drinking water as of June, below the 35 ppb recommendation but still above the EPA’s tighter non-enforceable limit of 0.35 ppb. 

Thousands of the so-called “forever chemicals” exist, with testing standards established to detect just a fraction of known PFAS (1,4-dioxane is not considered a PFAS). CFPUA regularly tests for 53. 

Combined PFAS (of which there is no official drinking water standard or advisory level) were measured at 109.31 ppb in finished CFPUA drinking water as of May 11, the most recent sampling results. This is the highest observation in a nine-month period. Testing standards are only established for two PFAS: PFOS and PFOA, set at a combined –– not individual –– health advisory limit of 70 ppb. CFPUA’s latest measurements of combined PFOS and PFOA are well below the federal recommendation, at 2.5 ppb as of June. 

The Environmental Working Group, an advocacy organization active in trying to get PFAS regulated, recommends a combined PFAS limit in drinking water at 1 ppb.

Levels of combined PFAS in finished and raw water at CFPUA have fluctuated over time. (Port City Daily/Courtesy CFPUA)


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