From wastewater to feed: Understanding PFAS occurrence in wastewater-irrigated crops

Reusing treated wastewater for irrigation is a sustainable way to recycle nutrients and reduce reliance on freshwater use. However, wastewater irrigation inadvertently introduces per- and polyfluoroalkyl substance (PFAS) into agroecosystems, causing concerns regarding potential adverse impacts to ecosystem, animal, and human health. Therefore, an improved understanding of the pathways by which PFAS accumulate in forage is needed. A greenhouse study was conducted to: (1) quantify the relative importance of root uptake versus foliar sorption of PFAS in corn and orchard grass; (2) assess potential plant health effects of irrigation with PFAS-containing wastewater effluent; and (3) determine the implications for bioaccumulation into the food chain. The greenhouse study was comprised of four treatments for each forage crop: (1) PFAS-contaminated agricultural soil watered with treated wastewater; (2) PFAS-contaminated agricultural soil watered with tap water; (3) control soil watered with treated wastewater; and (4) control soil watered with tap water. Results suggested that foliar sorption was an unlikely contributor to PFAS concentrations in crop tissue. Root uptake was identified as the predominant uptake pathway. PFAS were detected more frequently in orchard grass samples compared to corn silage samples. Additionally, corn exhibited a lower uptake of long-chain PFAS compared to grass. Overall, no plant health effects on growth attributable to PFAS concentrations were observed. Lastly, cattle exposure to PFAS was largely short-chain PFAS or long-chain “replacement” compounds (>50%). This study provides insights on PFAS entry into the food chain and potential implications for livestock and human health.