The EPA’s Fifth Unregulated Contaminant Monitoring Rule, or UCMR 5, shows PFAS in 200 additional public-water systems across the nation, adding approximately 7 million people to the risk pool. That brings the total exposed to PFAS-contaminated drinking water to over 172 million Americans. Figures reflect about 75 percent of systems tested under UCMR 5, with 3,309 sites showing PFAS presence and a total of 9,552 contaminated locations across the U.S. These data will be central to helping professionals track emerging risks and prepare effective, real-world responses to tackle them. This week, Water Treatment 411 dives into what these latest EPA numbers mean for your facility.
How UCMR 5 Updates Your Understanding
The UCMR 5 spans 2023–2025, requiring testing for 29 PFAS and lithium. It’s published about 83 percent of expected results through recent data releases, and you can access raw results, reference doses, and occurrence summaries via the Data Finder and quarterly data summaries. These will prove essential tools for planning risk assessments and response strategies moving forward. The EPA is expected to release more UCMR 5 results in the coming months.
The Regulatory U-Turn
In a controversial change, EPA announced it will keep enforceable MCLs for PFOA and PFOS, extend compliance deadlines from 2029 to 2031, and rescind MCLs for PFHxS, PFNA, GenX (HFPODA), PFBS, and the combined hazard index.
EPA frames this move as offering flexibility and cost relief for utilities. Critics argue it weakens public health safeguards and violates the Safe Drinking Water Act’s antibacksliding provision.
EPA has petitioned the D.C. Circuit to lift the stay on litigation challenging these MCLs. A briefing schedule is in place, with clarification due by September 10 and proposed schedule by September 17, 2025.
Your Tactical Moves
Don’t wait on the EPA. The uneven regulatory landscape demands proactive strategies now. Here are a few to consider:
- Roll out treatment upgrades targeting broader PFAS groups, not just PFOA/PFOS.
- Implement or reinforce home filtration recommendations in high-exposure areas. Remember, old or exhausted filters may do more harm than good.
- Invest in source control dialogue. PFAS can originate from industrial sites, chemical plants, and consumer product use, so work with a range of stakeholders to limit releases.
- Stay plugged into state-level policy, since many local governments are stepping in to regulate PFAS more tightly than the federal baseline. (Psst…. Water Treatment 411 has your back here. Subscribe for ongoing updates and policy tracking.)
The Reality Check
Based on current UCMR 5 data, an estimated 172 million Americans are exposed to PFAS-contaminated drinking water, a figure that likely underrepresents the true scale of contamination. At the same time, EPA’s regulatory rollback is moving forward, with compliance deadlines extended, multiple MCLs rescinded, active litigation underway, and a revised rule anticipated by spring 2026.
While the PFAS OUT technical assistance program may provide some support, it is no substitute for comprehensive treatment systems and rigorous monitoring infrastructure that can effectively safeguard public health. Expect more shifts in regulation, and consider investing in broader PFAS control to continue protecting public health no matter what Washington decides next.
SOURCES: EPA
