Statistical\nMapping of PFOA and PFOS in Groundwater\nthroughout the Contiguous United States

Per-and polyfluoroalkyl substances\n(PFAS) are synthetic chemicals\nthat are increasingly being detected in groundwater. The negative\nhealth consequences associated with human exposure to PFAS make it\nessential to quantify the distribution of PFAS in groundwater systems.\nMapping PFAS distributions is particularly challenging because a national\npatchwork of testing and reporting requirements has resulted in sparse\nand spatially biased data. In this analysis, an inhomogeneous Poisson\nprocess (IPP) modeling approach is adopted from ecological statistics\nto continuously map PFAS distributions in groundwater across the contiguous\nUnited States. The model is trained on a unique data set of 8910 PFAS\ngroundwater measurements, using combined concentrations of two PFAS\nanalytes. The IPP model predictions are compared with results from\nrandom forest models to highlight the robustness of this statistical\nmodeling approach on sparse data sets. This analysis provides a new\napproach to not only map PFAS contamination in groundwater but also\nprioritize future sampling efforts.