Motivated by “the quality and sustainability of drinking-water” due to rising water demand concerns in the United States, as well as “increasing contamination of drinking-water resources, and a growing understanding of potential human-health consequences associated with exposures to contaminants,” the U.S. Geological Survey recently conducted a study on the prevalence of PFAS in tap water.
To better understand human exposure to PFAS at the point-of-use, the authors conducted a standardized analytical survey of PFAS nationally.
“The overall objectives of the study were to (1) directly compare PFAS exposure in regulated public-supply tap water to tap water from unregulated private-wells, (2) provide information on potential aggregated human-health effects of PFAS using health-based screening tools, and (3) identify potential landscape-scale drivers of PFAS contamination in tap water,” the authors said.
In the United States, the EPA and related state-specific databases comprise PFAS testing results from samples collected from public drinking-water treatment plants after treatment and prior to distribution, “an approach that does not account for distribution-system changes that can affect consumer exposures at the tap.”
The authors noted that most national testing programs (e.g., EPA’s UCMR3) focus on community water supplies serving greater than, or equal to, 10,000 consumers, and “do not include private-wells and rarely capture information from rural communities (52 million people rely on small water supplies serving < 10,000).”
The authors believe that this indicates that “data on PFAS exposure and potential human-health effects … does not exist for over one-third of the US population …” Therefore, the authors pointed out that currently there is limited information that exists on drinking-water PFAS concentrations at the point of exposure (i.e., point-of-use tap water). Private well owners make up about 13–14 percent of the U.S. population (about 40 million people).
Specifically, for the study, tap water from 716 locations (269 private wells; 447 public supply) across the United States was collected during 2016–2021, including three locations where temporal sampling was conducted.
“The number of individual PFAS observed ranged from 1 to 9 (median: 2) with corresponding cumulative concentrations (sum of detected PFAS) ranging from 0.348 to 346 ng/L. Seventeen PFAS were observed at least once with PFBS, PFHxS and PFOA observed most frequently in approximately 15% of the samples.”
The upshot of the study is that the authors estimate that “at least one PFAS could be detected in about 45 percent of U.S. drinking-water samples.”
The authors also found that their results indicate that “1) detection probabilities vary spatially (8 percent in rural areas up to greater than 70 percent in urban areas/areas with a known history of PFAS contamination); 2) drinking-water exposures may be more common in the Great Plains, Great Lakes, Eastern Seaboard, and Central/Southern California regions, and 3) temporal variations in concentrations/detections may be limited.”