PFASs Forensic Characterization Methodology

Per- and Polyfluoroalkyl Substances

are a large family of complex and ever-expanding group of synthetic fluorinated organic chemical compounds. There are over 8,000 registered PFASs, each having unique chemical and physical properties as well as migration potential within the environment. These compounds have been developed to impart unique properties when applied to surfaces, including resistance to water, grease and stains, and are widely used to make various types of everyday products. PFASs are contained in most Class B firefighting foam (AFFF). PFOA and PFOS have been extensively manufactured and studied. Laboratory animal toxicology studies and human epidemiological studies suggest that adverse health effects may occur as a result from long-term exposure to certain PFASs at environmentally relevant levels. The USEPA completed toxicity assessments for the GenX chemicals and PFBS. They announced that five (5) additional PFAAs will be reviewed for toxicity assessment through the Integrated Risk Information System; but no timeline has been established. Estimating the physical and chemical characteristics of many PFASs continue to be active areas of research and investigation, including: site characterization, migration potential, and potential risks to humans and ecosystems.

PFASs Regulatory Setting

The contemporary PFASs regulatory setting is rapidly evolving. The USEPA classifies PFOS and PFOA as “emerging contaminants”: chemicals characterized by a perceived, potential, or real threat to human health or the environment; regulated under the Toxic Substances Control Act (TSCA). The USEPA has recently published the PFAS Strategic Roadmap: EPA's Commitments to Action 2021-2024, which goes into further detail about their approach to addressing PFAS contamination. Although there is limited guidance regarding the nature of PFASs in the environment, there are three (3) active areas of research and investigation:

1. Development of certifiable analytical laboratory methods which can quantify the concentration of PFASs in environmental media with Method Detection Limits nearing 2.0 parts/trillion (ppt);

2. Development of toxicity data to determine human health and ecological affects associated with PFASs exposure; and

3. Defining PFASs migration potential parameters such as absorptivity, decay rate and solubility.

Data collected during facility PFASs characterizations are being used to establish a baseline understanding of the environmental impacts from PFASs. Many state authorities are in the final stages of promulgating regulations and  developing interim guidance regarding PFASs corrective action limits. For example, on 6/1/2020, the state of New Jersey established Maximum Clean-Up Levels for two (2) PFASs (PFOA at 14.0 ppt and PFOS at 13.0 ppt).

Develop a PFASs Characterization Plan that can Differentiate Potential Sources

The complex nature of PFASs impacts within the environment together with the potential for contribution from multiple sources of PFASs dictate the need for a comprehensive, site-specific PFASs characterization plan. Leppert Associates’ PFASs Sampling and Analysis Plans (SAP) are designed to guide the collection and compilation of data which can be used to identify potential local PFASs sources. Our approach has  received regulatory approval for facilities located throughout the US. At a minimum, Leppert Associates data collection plans prescribe:

1.  Environmental media to be targeted;

2. Analytes selected for lab analysis;

3. Novel, regulatory accepted laboratory analytical methods;

4. Optimized data collection locations; and

5. Prescription of strict QA/QC protocols.

Regimented Media Sample Collection Following Strict QA/QC Protocols

Collecting media samples for certified analytical laboratory determination of PFAS concentrations requires significant experience and a detailed attention to prescribed quality assurance/quality controls protocols. The sampling team must follow strict QA/QC protocols to assure data meet established regulatory prescribed PFASs Data Quality Objectives (i.e. reporting limits approaching 2.0 ppt). Due to the potential presence of PFASs in: media sampling equipment; site construction materials (including well construction); and throughout the biosphere at low concentrations, sampling techniques which minimize cross-contamination are employed.

Evaluate Analytical Lab PFASs Results as Diagnostic Chemical Signatures

Analytical laboratory media concentration results are a primary source of precise and accurate data used to characterize PFASs occurrence within the environment. Our investigation plans request analytical laboratory certification of chemical compound results for between forty (40) & fifty-five (55) different PFASs. Analytical lab results are empirically evaluated as a family of chemical compounds having an identifiable chemical signature. A PFASs signature is delimited for each media sample. PFASs are grouped into ten (10) categories based on substance: toxicity, migration potential and whether it is a terminal product or a precursor product. For each media sample, concentrations reported for each PFAS included in a particular group are summed. The summed concentration for each group represents a diagnostic component of the sample’s chemical signature. PFASs signatures are graphically represented using recognized geochemical signature techniques; often as a Rose Diagram (shown).

Execute Forensic Analysis using PFASs Concentrations as Environmental Tracers

Data collected during a PFASs characterization may indicate the presence of PFASs at concentrations requiring corrective action consideration. Often, pervasive PFASs distribution within the local environment and the potential for off-site PFASs sources contributing to site media concentrations trigger the need for a forensics analysis to postdict potential PFASs sources. Leppert Associates forensic characterizations are performed using state-of-the-art, regulatory accepted: empirical analyses; process modeling; and conceptual modeling (simulation) techniques. These techniques are used to identify probable PFASs sources potentially comingling within site environmental media. PFASs chemical signatures, derived from site characterization media-quality data, are assessed as environmental tracers. Environmental tracers are chemical substances, released by human activities, that persist within the environment. Each tracer has a unique, quantified migration potential. The measured environmental media concentration of the tracer, its migration potential and an understanding of potential off-site sources are used to back-track the migration pathway from its source.