PFAS: Final considerations in developing a rule to address PFAS that may include MCLs

In March and April 2022, Aqua Talk blogs discussed initial steps that EPA will likely be considering as it moves forward in developing a rule to address  per- and polyfluoroalkyl substances (PFAS) that may include MCLs. The first blog post discussed timing and health risk considerations, while the second blog article started to dig into the many variables and decisions that EPA must make determinations on to develop the rule. These determinations include which systems the rule will apply to, the compliance and monitoring framework, public notice requirements including health effects language, and treatment considerations. In this last article of the series we will cover other issues involved with regulating PFAS and the possibility that EPA will regulate PFAS as a group, similar to how disinfection by-products are regulated, and require treatment techniques to remove PFAS, similar to the approach for cryptosporidium. 

As EPA approaches this PFAS rule, it will need to determine which PFAS to regulate and whether to regulate them separately, group them together, or establish an overall treatment technique. If EPA chooses to regulate PFAS individually, it would first establish a Maximum Contaminant Level Goal (MCLG) for each substance. The MCLG is the highest concentration that people can be exposed to with no anticipated health effects. For many contaminants, including carcinogens, MCLGs are set at zero (0). But MCLGs are not enforceable; they serve as public health goals. Then, EPA would consider laboratory detection and quantification issues, treatment technology effectiveness and costs compared to benefits as it sets the MCL values. However, in general EPA is required to set MCLs as close to MCLGs as possible within technical limitations, such as laboratory detection values. For PFAS, EPA will also need to give serious consideration to the challenges associated with disposal.

If EPA chooses to regulate PFAS as one or more groups, it must determine how many and which PFAS to include. This could be done based on similarity of health effects, chemical structures or other considerations. Once the group or groups are determined, then the process would work similar to the above. From May 2016 to June 2022, the health advisory grouped two PFAS compounds with the level set at 70 parts per trillion (ppt) for PFOA and PFOS added together. Prior to that time, and also starting again in June 2022, the health advisories were separate. In June 2022, EPA also set individual health advisories for PFBS and GenX chemicals. Vermont and Massachusetts used a grouping method to develop their state PFAS rules.

Another alternative at EPA’s disposal would be to establish a treatment technique rule for PFAS. A similar structure exists within the surface water treatment rule for cryptosporidium. If EPA took a similar approach to regulating PFAS, then it could establish a monitoring schedule where water systems would periodically monitor for PFAS at water sources or entry points. The group of PFAS compounds to be tested would likely encompass most or all of them captured by available laboratory methods. Then EPA would need to establish a single threshold or multiple thresholds for requiring treatment of the impacted sources. EPA would also need to define the technologies and other technical criteria associated with the treatment technique. The benefit of this approach would be that the public could be protected more quickly from compounds likely to have health effects, while there is still insufficient health study information available to set an MCL. One of the PFAS chemicals often associated with firefighting foam is PFHxS. It is found at sites in Colorado with PFAS contamination and does not yet have a health advisory, though EPA is working to develop one. No states have taken this approach in developing their own PFAS rules.

At this point, the overall approach that EPA will take to develop the national PFAS rule is uncertain, but we should not have too long to wait. EPA is expected to publish its draft PFAS rule in December 2022. This will trigger a public comment period when water systems, states and the general public can comment on it. Then EPA plans to finalize the rule by December 2023. That is a very fast pace for EPA to move through a rulemaking process, but there is strong momentum for that to happen. The draft rule will give us a peek at some of the key decisions likely to inform the final rule that we have covered in this series of three articles. We should also learn more about the effective date, compliance monitoring period and final compliance date as well. After a final rule is published, then the division will move forward with a stakeholder process to set Colorado’s PFAS rule. 

I hope these articles have provided a sense of what is involved with developing a national PFAS rule, the key decisions to be made and various considerations to be undertaken as well. Perhaps it has given some ideas on areas to focus attention on when a draft rule is published and spurred thoughts about the types of comments you may have. Whatever happens, we will continue to work forward together at keeping tap water safe.  Thank you.

➽ Ron Falco, P.E. Safe Drinking Water Program Manager