June 17, 2024
PFAS National Primary Drinking Water Regulation
On April 26, 2024, EPA finalized national primary drinking water regulations for six per- and polyfluoroalkyl substances (PFAS) and PFAS mixtures. [89 FR 32532] The final rule sets individual enforceable maximum contaminant levels (MCLs) and recommended maximum contaminant level goals (MCLGs) for five PFAS. The rule also sets an MCL and MCLG for mixtures of two or more of four specific PFAS at a hazard index of ≤1 (unitless). A hazard index is the sum of ratios of the four PFAS concentrations and their associated health-based water concentration levels. All public water systems (PWSs) must comply with the MCLs by April 26, 2029. [§141.6(l)]
Substance | MCLG | MCL |
|---|---|---|
Perfluorooctanoic acid (PFOA) | 0 | 4.0 ppt |
Perfluorooctane sulfonic acid (PFOS) | 0 | 4.0 ppt |
Perfluorohexane sulfonic acid (PFHxS) | 10 ppt | 10 ppt |
Hexafluoropropylene oxide dimer acid (HFPO-DA, GenX) | 10 ppt | 10 ppt |
Perfluorononanoic acid (PFNA) | 10 ppt | 10 ppt |
Mixtures containing two or more PFHxS, HFPO-DA, PFNA, and PFBS (perfluorobutane sulfonic acid) | HI ≤1.0 | HI ≤1.0 |
HI = hazard index
Source: McCoy and Associates, Inc.; adapted from 40 CFR §141.903(d).
A public “right to know” provision is included in the final rule, requiring public notification and consumer confidence report (CCR) submittals. Under Part 141, Subpart O, community water systems must submit CCRs annually to their customers. The CCRs must include information on PFAS detection and provide potential health effects if MCL violations occur. MCL violations require a tier 2 public notification as soon as practicable but no later than 30 days after a system detects a violation. [Part 141, Subpart Q, Appendix A]
The final rule also includes monitoring and reporting requirements for PWSs. PWSs must sample each entry point using a monitoring regime based on EPA’s standard monitoring framework for synthetic organic contaminants. PWSs must complete the initial monitoring within three years of the rule promulgation and conduct periodic compliance monitoring at a frequency based on sample results. The final rule is effective June 25, 2024.
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This document addresses issues of a general nature related to the federal environmental regulations. Persons evaluating specific circumstances dealing with the environmental regulations should review state and local laws and regulations, which may be more stringent than federal requirements. In addition, the assistance of a qualified professional should be enlisted to address any site-specific circumstances.
