The US EPA has finalized the Maximum Contaminant Level (MCL) for some of the Per- and Polyfluoroalkyl Substances (PFAS), which are a group of chemicals that have a variety of different health impacts after long term exposure through drinking water including thyroid, liver, kidney functions and development effects on fetuses. The following are the enforceable limits:
Perfluorooctanesulfonic acid (PFOS) MCL of 4 nanograms per liter (ng/L) or parts per trillion (ppt).
Perfluorooctanoic acid (PFOA) MCL of 4 ng/L or ppt.
Perfluorononanoic acid (PFNA) MCL of 10 ng/L or ppt.
Perfluorohexanesulfonic acid (PFHxS) MCL of 10 ng/L or ppt.
Hexafluoropropylene oxide dimer acid (HFPO-DA) and its ammonium salt (also known as a GenX chemicals) MCL of 10 ng/L or ppt.
The US EPA will also regulate the mixture of PFNA, PFHxS, HFPO-DA and Perfluorobutane sulfonic acid (PFBS) as a group Hazard Index.
Starting 3 years following rule promulgation (ie. year 2027), public water suppliers must start regular monitoring for compliance, including results in the Consumer Confidence Reports and conducting public notification for monitoring and testing violations.
Compliance with the MCLs will be required starting in 2029 (5 years following rule promulgation) to give public water suppliers time to implement treatment as required.
More details about the rule are available in the US EPA press release.
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