Update on New Hampshire PFAS Drinking Water Standards (MCLs)

In 2019, the New Hampshire Department of Environmental Services (NHDES) adopted rules that establish health-based drinking water standards or Maximum Contaminant Levels (MCLs) and Ambient Groundwater Quality Standards (AGQS) for four per- and polyfluoroalkyl substances (PFAS) that include:

• 12 parts per trillion (ppt) for perfluorooctanoic acid (PFOA)
• 15 ppt for perfluorooctane sulfonic acid (PFOS)
• 18 ppt for perfluorohexane sulfonic acid (PFHxS)
• 11 ppt for perfluorononanoic acid (PFNA)

The effective date upon which the rules became enforceable standards was September 30, 2019. However, effective December 31, 2019, the Merrimack County Superior Court issued a preliminary injunction barring enforcement of these rules due to the alleged failure of NHDES to appropriately consider the costs and benefits of the rules. Accordingly, there are currently no enforceable drinking water MCLs for the four chemicals. The former AGQS rule of 70 ppt for PFOA, PFOS, or combined concentrations of the two chemicals, as adopted by NHDES in 2016, remains in effect, while the 2019 rules are under an injunction. Please note that these rules do not require testing by owners of private water wells. NHDES does recommend for health reasons that private wells meet the standards.