RALEIGH — The North Carolina Department of Environmental Quality has submitted a human health risk assessment of 1,4-dioxane in drinking water, as directed by the General Assembly.
1,4-Dioxane is a clear liquid primarily used as a solvent in manufacturing processes that mixes easily with water and degrades slowly. The chemical is classified as a likely carcinogen by the U.S. Environmental Protection Agency, the U.S. Department of Health and Human Services, and the International Agency for Research on Cancer.
According to an EPA sampling program, North Carolina has the third highest measured concentration of 1,4-dioxane in drinking water in the nation. The state also ranked fourth-highest in the number of impacted drinking water systems, with most detections occurring in the Cape Fear River Basin.
The risk assessment concludes that North Carolinians are exposed to 1,4-dioxane concentrations that may be more than double the national average in drinking water and as much as four times the average in surface and groundwater.
The EPA has a Drinking Water Health Advisory Level of .35 ug/L for 1,4 dioxane in waters classified as water supplies.
The North Carolina Department of Environmental Quality has identified the City of Greensboro’s T.Z. Osborne Wastewater Treatment Plant, as a contributor to 1,4 dioxane in water sources, one of which is the Haw River, which flows to the Cape Fear.
According to NCDEQ data from last year, the facility reported a maximum concentration of 1,000 ug/L through 2019.
Though high amounts of 1,4-dioxane may be in untreated water sourced from the Cape Fear River, the water is filtered through the Cape Feear Public Utility Authority’s Sweeney Water Treatment Plant before consumption.
CFPUA began voluntary testing for 1,4-dioxane in 2017, CFPUA Vaughn Hagerty told PCD in 2019. The utility measured the likely carcinogen once in 2017 (0.18 ppb in finished water) and twice in 2018 (0.23 and 0.32 ppb in finished water).
As of April 2, 2024, CFPUA is reporting .47 in untreated water and .22 ug/L in finished water.
NCDEQ’s latest assessment is available online.
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