PFAS in Peri-Urban Agricultural Water: Assessing the Hazard Index in an Organic Farming Environment in Maryland, USA

Global efforts to quantify per- and polyfluoroalkyl substances (PFAS) in irrigation water sources have substantially advanced understanding of their potential impacts on human health. The proposed Hazard Index (HI) tool can be used to assess the health risks of PFAS chemical mixtures. To address potential health impacts, irrigation water samples were collected from two organic farms and analyzed to quantify PFAS under non-ideal agricultural conditions with no known direct PFAS input. Results show perfluorobutane sulfonic acid (PFBS) (37 ng/L), perfluorobutanoic acid (PFBA) (24 ng/L), and perfluorohexanoic acid (PFHxA) (22 ng/L) as the most abundant PFAS compounds at agricultural site 1 (AG1). The HI indicates compliance with perfluorohexane sulfonic acid (PFHxS)_branched (0.39) and non-compliance with PFHxS_linear (1.51) when calculated at AG1. Additional results show the presence of hexafluoropropylene oxide dimer acid (HFPO-DA; GenX; 28 ng/L) at agricultural site 2 (AG2), where no known industrial activity, PFAS-containing compounds (e.g., pesticides) are distributed, or PFAS-related manufacturing facilities exist in the area of influence. The HI indicates non-compliance at AG2 (HI = 2.83) for AG2, with GenX contributing much of the calculated risk. These findings suggest the HI may serve as a useful water health indicator for small sites exhibiting very low PFAS concentrations.