EPA’s Integrated Risk Information System (IRIS) program released a draft toxicological review of perfluorohexanoic acid (PFHxA) today, signaling another step in the agency’s ongoing research and regulatory initiatives focused on per- and polyfluoroalkyl substances (PFAS). This particular PFAS will be interesting to monitor because it is a breakdown product of other PFAS that may enter the environment through wastewater discharges, post-consumer product use and disposal, and other avenues. PFHxA has been detected in surface and groundwater, raising the potential for exposure through drinking water, but EPA is also evaluating other exposure pathways, including inhalation and dermal contact. Water sector followers can gain valuable insight in predicting future potential regulatory actions related to PFAS by monitoring EPA’s toxicity research and draft assessment process, as understanding and quantifying a chemical’s potential toxicity is foundational to whether and how the agency might later decide to regulate it.