The case for a more precise definition of regulated PFAS

Area of Science:

• Environmental Chemistry
• Chemical Regulation
• Organic Chemistry

Background:

• Per- and polyfluoroalkyl substances (PFAS) are a diverse group of organo-fluorine compounds with widespread environmental presence.
• Current definitions of PFAS may be too broad, encompassing substances with limited environmental persistence or toxicity.
• There is a need for a refined definition to accurately assess and regulate PFAS impacts.

Purpose of the Study:

• To advocate for a more precise definition of PFAS.
• To exclude compounds with single CF3-, -CF2-, or -CF- groups and those degrading to trifluoroacetic acid (TFA).
• To establish a technically sound basis for PFAS discussions and regulation.

Main Methods:

• Reviewing existing definitions of PFAS.
• Proposing the U.S. Environmental Protection Agency's definition as a suitable model.
• Analyzing the structural criteria for PFAS identification.

Main Results:

• The U.S. EPA definition of PFAS as "per- and polyfluorinated substances that structurally contain the unit R-(CF2)-C(F)(R1)R2" with specific saturation and non-hydrogen R-group criteria is presented as an example.
• This definition excludes compounds with single CF3-, -CF2-, or -CF- groups and those that degrade to TFA.
• Adoption of such a definition would enhance technical and regulatory clarity.

Conclusions:

• A precise definition of PFAS is crucial for effective environmental risk assessment and management.
• Focusing on specific structural characteristics, like those in the U.S. EPA definition, will improve regulatory efforts.
• Implementing a refined PFAS definition will advance technical understanding and regulatory action on impactful organo-fluorine compounds.