Occurrence of per- and polyfluoroalkyl substances in tap drinking water in British Columbia, Canada

Per- and polyfluoroalkyl substances (PFAS) are high-priority pollutants posing significant environmental and health risks. British Columbia, Canada, is a large province in which communities rely on diverse drinking water sources with varying potential for PFAS contamination. However, research on PFAS occurrence in Canadian drinking water, particularly in British Columbia (BC), remains limited. This study presents the first province-wide, comprehensive assessment of PFAS in BC's tap water, analyzing 120 samples collected across the province and targeting 31 PFAS compounds with detection limits of 0.008-2.5 ng L^-1. While most total PFAS concentrations were below Health Canada's guideline of 30 ng L^-1, four samples exceeded this threshold. Short-chain PFAS (C6 and shorter) were detected in 74.5% of samples with detectable PFAS, which is consistent with the phase-out of long-chain PFAS, the environmental transformation of precursor compounds, and the greater mobility of short-chain PFAS. Centralized water systems exhibited consistent PFAS concentrations and composition profiles, whereas decentralized systems showed greater variability and appeared more susceptible to PFAS contamination, likely due to diverse contamination sources in the surrounding areas. Since most PFAS levels were low, further efforts should prioritize the small subset of communities with higher concentrations, representing 3.5% of samples collected in this study, and account for the relatively higher prevalence of non-regulated short-chain PFAS.