A new study from North Carolina State University reveals a sobering truth about per- and polyfluoroalkyl chemicals (PFAS) – it could take over 40 years to flush them out of contaminated groundwater. These persistent chemicals, once used extensively in industries, have now become an environmental nightmare, with far-reaching consequences for communities reliant on the affected water sources. This article explores the implications of this finding and the challenges faced in addressing the PFAS crisis. PFAS and groundwater contamination are the key focal points.
Groundwater Woes: A Decades-Long Battle
The study, led by researchers at North Carolina State University, examined PFAS contamination in the groundwater of the Cumberland and Bladen counties in North Carolina. Using a novel combination of data, including groundwater age-dating tracers and groundwater flux, the researchers were able to forecast the future levels of PFAS in the groundwater discharging into tributaries of the Cape Fear River.
The findings are both alarming and sobering. The researchers detected PFAS in groundwater samples up to 43 years old, with average concentrations of the two most commonly found PFAS, hexafluoropropylene oxide-dimer acid (HFPO−DA) and perfluoro-2-methoxypropanoic acid (PMPA), at 229 and 498 nanograms per liter (ng/L) respectively. For context, the maximum contaminant level (MCL) set by the U.S. Environmental Protection Agency for HFPO-DA in public drinking water is just 10 ng/L.
A Multi-Decade Challenge: Flushing Out PFAS
According to the study, it could take decades for natural groundwater flow to flush out the lingering PFAS contamination, even with significantly lower air emissions since 2019. The researchers estimate that the process could take at least 40 years, and potentially longer if the PFAS diffuses into and out of low-permeability zones, such as clay layers and lenses, beneath the water table.
The study’s lead author, David Genereux, a professor at NC State, explains the gravity of the situation: “These results suggest it could take decades for natural groundwater flow to flush out groundwater PFAS still present from the ‘high emission years,’ roughly the period between 1980 and 2019. And this could be an underestimate; the time scale could be longer if PFAS is diffusing into and out of low-permeability zones (clay layers and lenses) below the water table.”
Tackling the PFAS Crisis: Challenges and Opportunities
The PFAS contamination issue extends beyond the immediate impact on groundwater, as the researchers point out. The affected groundwater discharges into tributaries of the Cape Fear River, which in turn impacts downstream users of the river water, including the population in and near Wilmington.
The study also notes that while air emissions of PFAS have decreased substantially since 2019, they have not been eliminated entirely. This means that some amount of atmospheric deposition of PFAS is likely to continue, further complicating the efforts to address the problem.
The researchers are committed to building on this work, with plans to model future PFAS levels at individual drinking water wells and collaborate with toxicologists to understand the potential health impacts of past PFAS exposure. These efforts will be crucial in developing effective strategies to mitigate the long-term consequences of this persistent environmental issue.
