Regional assessment of PFAS in drinking water in Miami-Dade and Palm Beach, South Florida: Implications for environmental exposure and exploratory links with liver cancer mortality.

Per- and polyfluoroalkyl substances (PFAS) are persistent anthropogenic contaminants of growing environmental and public health concerns. This study presents a regional assessment of PFAS contamination in tap water (n = 147) across 18 ZIP codes in Miami-Dade (MD) and 22 ZIP codes in Palm Beach (PB) counties, South Florida, U.S., selected according to liver cancer mortality quartiles to explore potential PFAS exposure-health associations. Sixteen PFAS were analyzed using solid phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Concentrations were higher in MD (mean ∑16PFAS = 79.6 ng/L) than in PB (10.2 ng/L). In MD, short-chain PFAS dominated (63 %), indicating potential fluorotelomer degradation and airport activities sources. PB had 56 % of long-chain PFAS, consistent with legacy contamination and deeper aquifer inputs. Exploratory nonparametric analyses identified compound-specific differences across liver cancer mortality quartiles; however, these patterns were attenuated after adjustment for population size, age, socioeconomic indicators, and county in ZIP code-level quasi-Poisson models, indicating no independent associations with liver cancer mortality. Principal component analysis indicated water supplier-level variability in PFAS profiles, with short-chain PFCAs driving variance in MD and mixed sources influencing PB. Exceedances of the U.S. EPA's Maximum Contaminant Levels (MCLs) were frequently observed for PFOA and PFOS in MD (56-99 % of samples), whereas exceedances in PB were limited (≤20 % for PFOS). Overall, this study provides a ZIP code-level regional assessment of PFAS occurrence and regulatory relevance in South Florida and frames exposure-outcome patterns as exploratory, supporting future longitudinal and individual-level investigations.