Per- and polyfluoroalkyl substances, commonly referred to as PFAS, may take more than 40 years to completely clear from contaminated groundwater in Cumberland and Bladen counties of North Carolina, according to a recent study conducted by North Carolina State University. This research utilized an innovative mix of PFAS data, groundwater age-dating markers, and groundwater flow rates to predict PFAS levels in groundwater that flows into the tributaries of the Cape Fear River.
The team collected groundwater samples from two watersheds near the Fayetteville Works fluorochemical facility in Bladen County.
According to David Genereux, a professor of marine, earth, and atmospheric sciences at NC State and the study’s lead, “A large area of groundwater contaminated with PFAS affects both residential and agricultural lands, impacting the local population in two significant ways.”
He explained, “Over 7,000 private wells are affected directly by this contamination. Additionally, groundwater that contains PFAS flows into tributaries of the Cape Fear River, which poses a risk to people using river water downstream, particularly around Wilmington.”
The research team analyzed the samples to identify types and concentrations of PFAS, and then combined this with groundwater age markers, contamination data from the N.C. Department of Environmental Quality, and groundwater flow rates to build a model that predicted historical and future PFAS concentrations in the groundwater that discharges into tributary streams.
PFAS was detected in groundwater that was as old as 43 years, with the most common substances — hexafluoropropylene oxide-dimer acid (HFPO−DA) and perfluoro-2-methoxypropanoic acid (PMPA) — showing average concentrations of 229 and 498 nanograms per liter (ng/L), respectively. In comparison, the maximum contaminant level (MCL) set by the U.S. Environmental Protection Agency for HFPO-DA in drinking water is 10 ng/L, which is an enforceable safety standard.
Genereux noted, “These findings indicate that it might take decades for the natural flow of groundwater to cleanse PFAS remaining from the high emission years, which were approximately between 1980 and 2019. This estimate could be conservative; if PFAS is seeping into and out of less permeable areas, like clay layers below the water table, the timeframe could extend beyond 40 years.”
The researchers emphasized that while emissions of PFAS into the air have dropped significantly since 2019, they haven’t stopped entirely, meaning atmospheric PFAS deposition will likely continue to contribute to groundwater contamination.
Genereux stated, “Even in a best-case scenario, where there is no further atmospheric deposition, the PFAS released in previous decades will gradually move from groundwater to surface water for another 40 years. We anticipate that PFAS contamination in groundwater will be an issue that spans multiple decades, and our research provides specific projections for this situation. We intend to expand upon this study by modeling future PFAS levels at specific drinking water wells and collaborating with toxicologists to connect past PFAS concentrations at those wells to measurable health effects.”
