PFAS As a Contaminant Class in a Changing Regulatory Environment

As per- and polyfluoroalkyl substances (PFAS) have emerged as contaminants of concern, the approach to regulating them has largely been to focus on individual compounds. State and Federal regulations have established maximum contaminant levels (MCLs) for five PFAS compounds. However, there are nearly 15,000 PFAS compounds that have seen at least some use since the 1930s, suggesting the need for a new approach to regulating these compounds as a class.

PFAS typically occur in the environment as mixtures of multiple PFAS compounds, so exposure typically occurs simultaneously to multiple PFAS compounds.  Regulation as a class can be accomplished in several ways, including 

• by hazard index where exposures to multiple PFAs are summed;
• by relative potency, where each compound is evaluated relative to a reference compound;
• or by total concentration, where concentrations of all PFAS compounds are summed.

A key benefit of making it a contaminant class would be consistency and standardization in addition to more directly addressing real exposures. Currently, nearly every state has some form of regulation around either PFAS compounds or products that contain them, such as aqueous film-forming foam (AFFF), in addition to overall federal regulation. Treating PFAS as a class would assist in both standardizing guidance and limiting confusion for stakeholders, as well as simplifying the regulating process. Similarly, it would provide guidance for less well-known compounds that may be encountered in the field by regulators and consultants.

The difficulty, however, is in the ubiquity of PFAS itself. PFAS compounds were, and in some cases still are, widely used across a wide range of consumer products and industries, often in waterproofing, lubrication, or “non-stick” applications. Due to the strength of the bond between carbon and fluorine, it’s difficult to eliminate or destroy, and thus can be found and transmitted through water, air, and soil.

Another issue is that current MCLs for PFAS are extremely low relative to other classes of contaminants, with standards set at parts per trillion, or ppt. As an example of scale, this is one thousand times less, as a unit, than lead in federal standards. This presents challenges in setting appropriate action levels, as well as in monitoring and testing. 

A final concern with regulating individual PFAS compounds is that it takes time to develop individual standards and with the ubiquity of PFAS in consumer products and the environment, development of standards is limited by the lack of an unexposed population for comparison of toxic effects (control group).   Regulating as a class could potentially speed up the regulatory process and avoid “reopeners”, sites that reopen settled claims due to regulatory changes or new information about site conditions, due to promulgation of standards for other compounds.  PFAS will be an issue for years into the future, and careful regulatory standards are needed to ensure that it’s treated safely and effectively.