National Drinking Water Standard for PFAS


On March 14, 2023, the Biden-Harris administration announced its proposal for a first-ever National Primary Drinking Water Regulation (NPDWR) for six per- and polyfluoroalkyl substances (PFAS). The legally proposed enforceable limits are 4 parts per trillion (ppt) for perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). If finalized as proposed, public water systems (PWSs) have 3 years to bring their systems into compliance.

PFAS, also known as “forever chemicals” due to a strong chemical bond that makes them hard to break down, are a category of manufactured chemicals that can cause serious health problems, including cancer, if people are exposed to them over a long period of time. When drinking water is contaminated with PFAS, it can be a significant portion of a person’s total PFAS exposure.

“PFAS tend to co-occur with each other,” according to the EPA PFAS website. “This regulation will also remove many other PFAS when they co-occur with these six regulated PFAS. EPA is following recent peer-reviewed science that indicates that mixtures of PFAS can pose a health risk greater than each chemical on its own. Concurrent with the proposed PFAS NPDWR, which was published in the Federal Register on March 29, 2023, the EPA also announced it is making preliminary regulatory determinations for [perfluorononanoic acid (PFNA)], GenX Chemicals, [perfluorohexane sulfonate (PFHxS)], and [perfluorobutanesulfonic acid (PFBS)] in accordance with the Safe Drinking Water Act regulatory development process. EPA proposes to regulate PFNA, GenX Chemicals, PFHxS, and PFBS using a Hazard Index formula.”

If finalized, the proposed rule would establish:

Maximum contaminant levels (MCLs) and maximum contaminant level goals (MCLGs) for PFOS and PFOA;

A Hazard Index for PFHxS, GenX chemicals, PFNA, and PFBS;

Monitoring requirements for PWSs;

Reporting requirements for PWSs that are community water systems; and

Treatment requirements for reducing PFAS levels for PWSs.

MCLGs and MCLs

“MCLGs are non-enforceable public health goals,” states the EPA Fact Sheet on the proposal. “MCLGs consider only public health, not the limits of detection and treatment technology effectiveness. Therefore, they are sometimes set at levels which water systems cannot meet because of technological limitations. For example, if a contaminant is a known or likely carcinogen, EPA sets the MCLG at 0. MCLGs also consider adverse health risks to sensitive groups, including infants, children, the elderly, and immuno-compromised individuals. Once the MCLG is established, EPA determines the MCL. MCLs are enforceable standards. An MCL is the maximum level of a contaminant allowed in drinking water, which can be delivered to users of a [PWS]. For this rule proposal, EPA evaluated available methods and treatment technologies, that are shown to measure and remove these six PFAS and set the proposed MCLs as close as possible to the MCLGs. EPA also evaluated costs and benefits in determining the proposed MCLs.”

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EHS Daily Advisor, 04-04-23