A Fundamental Distinction: Regulatory Compliance vs. Health Protection
Water utilities achieving PFAS MCL compliance have met their legal obligations—a meaningful and important accomplishment requiring significant investment. But consumers and public health advocates deserve to understand that regulatory compliance and health protection, while overlapping, are not identical. This distinction is particularly important for PFAS, where the regulated six compounds represent a fraction of the PFAS universe in contaminated water.
Thousands of PFAS Compounds, Six Regulated
EPA’s MCL rule covers PFOA, PFOS, PFNA, PFHxS, HFPO-DA, and PFBS. An estimated 4,700+ PFAS compounds exist. The gap between regulated and total PFAS represents a compliance-protection disconnect: water below all MCLs can contain hundreds of unregulated PFAS at concentrations that may individually or cumulatively present health risks not captured in current standards.
The Short-Chain Treatment Gap
Even within the regulated six, the treatment gap persists: activated carbon—the dominant compliance treatment—cannot reliably remove PFBS below its 2,000 ng/L MCL at the low concentrations that health science suggests are harmful. A utility reporting PFBS at 1,800 ng/L (below MCL) in GAC effluent is technically compliant while delivering a compound at concentrations that may present health risks the high MCL does not reflect.
What Comprehensive Protection Would Require
True comprehensive PFAS protection—going beyond regulatory compliance—would require: monitoring for all PFAS using non-targeted analysis, treatment capable of removing short-chain and emerging PFAS as effectively as long-chain compounds, and standards based on cumulative PFAS burden rather than individual compound thresholds. No currently deployed technology meets these goals comprehensively, highlighting the frontier that next-generation PFAS treatment must address