The Science-Regulatory Pipeline for PFAS
The journey from PFAS health research findings to enforceable water treatment standards involves multiple steps—epidemiological research, risk assessment, regulatory action levels, MCL development—each with its own timeline and decision criteria. Understanding this pipeline helps explain why treatment requirements are constantly evolving and why today’s compliant water may not be tomorrow’s standard.
Health-Based Values and MCL Derivation
EPA derives maximum contaminant level goals (MCLGs) from health-based values using reference doses (RfD) for non-cancer effects and cancer risk ranges. For PFOA and PFOS, the MCLG is zero (reflecting inability to establish a safe threshold for carcinogens). The MCL of 4 ng/L reflects the lowest concentration achievable by best available treatment technology—treatment feasibility sets the regulatory floor above the health-based goal.
How Emerging Research Changes Treatment Needs
As epidemiology reveals health effects at lower and lower exposure concentrations, both MCLGs and MCLs face potential future tightening. The 2024 MCLs of 4 ng/L were substantially more stringent than the 2016 health advisory of 70 ng/L—a 17-fold tightening driven by improved health research. Treatment systems designed for 70 ng/L compliance were suddenly non-compliant at 4 ng/L, requiring capital reinvestment that exemplifies the treatment challenge of a moving regulatory target.
Future PFAS Regulatory Evolution
Research pipelines suggest additional PFAS MCLs for currently unregulated compounds are likely as health evidence accumulates. Treatment systems being designed today should consider flexibility to address additional regulated compounds—including short-chain PFAS that current regulations allow at high concentrations. Adaptive treatment infrastructure design that can incorporate additional treatment capabilities as regulations evolve provides the most cost-effective long-term compliance pathway