On March 14th, U.S. EPA released its advanced pre-publication notice of proposed rulemaking which, if finalized, will establish for the first time national drinking water standards for PFAS under the Safe Drinking Water Act (SWDA).  While many states have adopted drinking water standards, the U.S. EPA has yet to establish any national drinking water standards for PFAS.  The implications if this rule is finalized will be very significant as discussed below.

What is the anticipated timing of the draft and final rule?

The proposed rule has not yet been published in the federal register but is scheduled to published on March 29th.  Once it is published, U.S. EPA will have a sixty (60) day public comment period.  U.S. EPA has stated their goal is to finalize the standard by the end of 2023.

What standards is EPA proposing and for which PFAS compounds?

When establishing new drinking water standards, U.S. EPA first establishes a Maximum Contaminant Level Goal (MCLG), which are non-enforceable public health goals.  The MCLG is based on current scientific analysis of the risk presented by the chemical compound. With regard to PFOA and PFOS, EPA’s review of the scientific literature resulted in it designation of PFOA and PFOS as likely carcinogens (specifically liver and kidney cancer).  EPA’s proposed rulemaking concludes that the MCLG for the PFOA and PFOS compounds is zero.  EPA has determined that there is “no dose below which either chemical is safe.” 

While the MCLG is based on a determination of the level of exposure which is determined to be safe, the actual regulatory standard –  Maximum Contaminant Level (MCL) – takes into consideration two additional practical considerations when establishing the standard: 1) what is the lowest detection level that labs across the country can reliably detect (i.e., the lab analytical detection limit); and 2) the level proven treatment technologies are capable of achieving.

From the U.S. EPA’s proposed rulemaking, the primary driver in establishing the MCL for PFOA and PFOS was the lab analytical detection limit using EPA’s recognized laboratory procedures (i.e., EPA methods 533 and 537.1).  In theory, this means that if labs get more sophisticated in reliably measuring levels of PFOA and PFOS below 4 ppt, the standards could go even lower.

Here is a summary of the proposed standards:

CompoundsProposed Maximum Contaminant Level
PFOS4 parts per trillion (4.0 ng/l)
PFOA4 parts per trillion (4.0 ng/l)
PFHxSHazard Index = 1.0
GenX ChemicalsHazard Index = 1.0
PFNAHazard Index = 1.0
PFBSHazard Index = 1.0

What is the Hazard Index? 

EPA concludes that persons exposed to a mixture of PFAS compounds can have a so called “dose additive” response, which means health impacts can occur at lower levels than if exposed to that compound alone.  To address the risk of exposure to a mixture of PFAS compounds, EPA decided to propose a drinking water standard tied to a hazard index of 1.0 for the remaining four PFAS compounds.

Every drinking water system would measure the levels of these four compounds in their system.  The levels would be compared to the following Health-Based Water Concentration (HBWC), which is the level no health effects are expected for that specific compound. Because EPA determined the MCLG for PFOA and PFOS is zero, both of these compounds are not considered in the health index analysis.  

The measured value is divided by the HBWC then those four values are added together.  If the total sum of those values is greater than 1.0 it is considered a violation of the standard.  The HWBC’s for each of the four compounds are as follow:

CompoundHBWC (ppt)
GenX Chemicals10

If the rule goes final what requirements will apply to public drinking water systems?

Initial monitoring of the system will be required within three years after the rule’s promulgation.  Systems must be in compliance with the MCL and health index within three years.  Due to the engineering planning and construction timeframes, public drinking water systems will likely need to initiate engineering shortly after the rule is final in order to have treatment systems in place within the three year time period allowed for compliance.  There are recognized treatment systems that are effective in removing PFAS compounds, including activated carbon, anion exchange (AIX) and high-pressure membrane technologies.  All of these treatment systems are expensive to install and have ongoing operation & maintenance (O&M) costs.  Another issue is that the material used to filter PFAS, such as carbon filter, must be managed as a PFAS containing waste, which increases disposal costs.  As discussed below, due the large number of public drinking water systems that could be affected, the rule will result in very significant compliance costs during the 2024-2026 time period.

EPA’s analysis of cost of compliance and anticipated health benefits

When developing new MCLs under the Safe Drinking Water Act, U.S. EPA is required to analyze the anticipated health benefits and cost of compliance of the proposed rule.  EPA estimates there are approximately 66,000 public drinking water systems that could be affected by the rule.  The proposed rule includes a very detailed cost/benefit analysis of the proposed rule.  EPA used a time period of 80 years to evaluate the annual cost and annual health benefit of the proposed rule.  EPA’s analysis included a range of estimated annualized compliance costs of between $700 million to $1.3 billion dollars.  While this is an oversimplification from EPA’s proposed rule, over an 80 year time frame, the total cost would have estimated range of between $56 billion to $104 billion.  However, those costs will be front loaded because the most significant engineering and construction costs will be in the early years as drinking water systems install treatment. 

What is the next significant regulatory action anticipated by EPA regarding PFAS?

EPA has indicated it will propose a rule designating PFOA and PFOS as “hazardous substances” under CERCLA sometime in the summer of 2023.  If PFOA and PFOS are defined as hazardous substances under CERCLA, it will provide clear legal authority to those seeking cleanup of property contaminated by PFAS.