PFAS exposure modelling and trigger points for investigation in recycled water irrigation applications

‘PFAS’ are a large class of chemical compounds, some of which can bioaccumulate or be toxic to humans and animals. Three PFAS: PFOS, PFOA and PFAS3; have been comprehensively investigated. An earlier study (WaterRA Project 2046) found PFAS in recycled wastewater and this raised concerns that crops irrigated with recycled water might lead to long-term chronic toxicity or bioaccumulation in soils. This research used existing datasets about PFOS, PFOA and PFAS3 to build a predictive conceptual model: the PFAS Exposure Model for Irrigation (PEMI). This was used to derive ‘Trigger Points for Investigation’(TPI); the levels of PFOS or PFOA or PFAS3 that, when measured in soil or recycled water, are high enough to cause concern and trigger investigation and action. Levels lower than the TPI’s are considered ‘safe’, and the PFAS3 TPI was higher than the median concentration measured in recycled wastewater from 17 Australian treatment plants (Project 2046). While these TPI are an excellent start to ongoing environmental and safety monitoring, the authors note that more data and research about plant uptake, animal transfer, degradation and leaching of additional PFASs will help validate and improve the PEMI.