The North Carolina Department of Environmental Quality has prepared and submitted a human health risk assessment of 1,4-dioxane in drinking water, as directed by the General Assembly (Session Law 2023-137, Section 9(b).)

1,4-Dioxane is a clear liquid primarily used as a solvent in manufacturing processes. It 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 3rd highest measured concentration of 1,4-dioxane in drinking water in the nation. The state ranked 4th 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.

DEQ enlisted assistance from experts in the field and used the latest scientific information to complete the assessment.  DEQ’s human health risk assessment supports the application of a science-based cancer slope factor in determining a water quality standard for 1,4-dioxane that provides protection of drinking water supplies.

DEQ continues to use its existing authority under state and federal law to address 1,4-dioxane discharges and protect public health and drinking water supplies.

The assessment is available online.

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