One of the potential challenges with starting and completing site characterizations for PFAS compounds (in addition to the lack of approved cleanup standards for many of the environmental media) is the lack of approved and/or certified laboratory analytical methodologies, both at the federal and state levels (in many states), for media other than drinking water and groundwater.

As noted by ITRC in its Site Characterization Considerations, Sampling Precautions, and Laboratory Analytical Methods for Per- and Polyfluoroalkyl Substances (PFAS) (April 2020):

USEPA Method 537.1 and USEPA 533 contain specific requirements for sample preparation and analysis of finished drinking water samples. Currently, there are no USEPA methods for the preparation and analysis of other sample media.”  [Emphasis added.]

Later, ITRC explains:

Without a standard method for media other than drinking water, laboratories’ methods may vary greatly in their precision and accuracy.”

This issue is important to keep in mind both in undertaking an investigation and in evaluating or relying on data that have previously been collected.