The Landscape of PFAS Contamination in the United States: Sources and Spatial Patterns

The scope and scale of per-and polyfluoroalkyl substances (PFAS) contamination remains unknown. Using two nationwide data sets, we provide a profile of PFAS contamination in the United States and compare site categories with groundwater PFAS detections to identify site characteristics and sources of concern. We use data from the PFAS Project Lab's Known PFAS Contamination Tracker (N = 2219) and presumptive PFAS contamination data set (N = 79,891), developed to characterize the distribution of known and likely PFAS sources. In this data set, all categories of known PFAS contamination sites are associated with average groundwater PFAS concentrations above health-based regulatory levels (4 ppt); 94% of detections exceed this limit. Aqueous film-forming foam (AFFF) use was associated with the highest average PFAS detections in this data set, and metal plating facilities account for the greatest proportion of industrial contamination sites that likely utilize PFAS (53%), though we also identified testing gaps of non-AFFF contamination sources. We conducted spatial cluster analyses, identifying hotspots of PFAS sites at national and regional levels. These findings can support multiscale approaches to PFAS remediation, including testing, siting, permitting, and community outreach, though cautious interpretation is necessary because of data set limitations. This analysis demonstrates the utility of a presumptive contamination model.