Lessons From Dioxins And PCBS Inform Smarter PFAS Site Investigations

Insights from decades of intense scrutiny of dioxins and PCBs in the environment, beginning in the 1960s, remain pertinent to our current challenges with PFAS. The lessons learned regarding detection and measurement, exposure, toxicity, and the investigation of dioxin- and PCB-contaminated sites are applicable to PFAS. George and Birnbaum (2024) ¹ provide an excellent review of this topic. Here, I highlight several practical considerations for risk assessment and site and source investigations.

Detection and Measurement

U.S. federal and state environmental agencies, along with several countries, have established health advisories for PFAS. However, the current limitations of PFAS analytical methodologies hinder environmental investigations that prompt these advisories ³. At present, among the thousands of unique PFAS substances, USEPA-approved laboratory testing methods apply to only 29 compounds in drinking water and 40 in wastewater, surface water, groundwater, soil, biosolids, sediment, landfill leachate, and fish tissue. Although PFAS analytical methods continue to advance, significant challenges persist in verifying their presence and accurately measuring concentrations in air, food, groundwater, sediment, soil, and surface water ³.

Measuring total dioxins or total PCBs and using screening tools like CALUX for dioxins have limited utility in risk assessment and environmental investigations. Similarly, evaluating total organic fluorine (TOF) or total adsorbable fluorine (AOF) has also shown limited utility for PFAS. Although TOF or AOF testing is often promoted as a screening tool for PFAS, positive results do not exclude the possibility that the fluorine originates from non-PFAS sources. A federal judge in California correctly ruled in Bounthon v. The Proctor & Gamble Company (Case No. 23-cv-00765-AMO) that relying on TOF screening for PFAS is insufficient for definitively confirming the presence of PFAS or specific PFAS compounds in consumer products. Improved analytical methods are still needed to clarify environmental risks and site cleanup strategies for PFAS.

Environmental sampling presents significant pitfalls. The ubiquitous nature of dioxins has prompted considerable attention to field sampling and laboratory methods for preserving the integrity of environmental samples and analyses, even in recent years ⁴. The potential for PFAS cross-contamination during sampling is well-established ⁵. Due to their prevalence in everyday items such as sampling gear, clothing, and food wrappers, even well-intentioned investigations can yield false positives. Laboratories capable of accurately detecting PFAS at parts-per-trillion levels remain relatively limited. Poor analytical detection thresholds and testing methods across jurisdictions add further complications and invite disputes regarding sample integrity and contamination levels ⁶.

Exposure and Risk

Understanding the historical evolution of dioxin and PCB risk assessment methods informs effective regulations and public health strategies for PFAS. For example, experiences with dioxin and PCB exposure assessments highlight dietary intake, particularly from contaminated food sources such as meat and dairy, as a significant pathway for persistent chemicals moving through food webs ⁷.

Dioxin risk assessment methodologies can guide the development of a similar calculation framework applicable to PFAS, emphasizing essential cancer and non-cancer endpoints and dermal, ingestion, and inhalation exposure pathways. Approaches such as using Biological Exposure Ratios (BERs), which integrate toxicity data and anticipated human exposure levels, can facilitate a structured evaluation for PFAS risk assessment ⁸. Bioaccumulation factors (BAFs) and biota-sediment accumulation factors (BSAFs) related to PFAS, comparable to those established for dioxins and PCBs, could be derived from existing models to estimate ecological impact ⁹.

Toxicity

While dioxins are also persistent and toxic ¹⁰, the larger number of PFAS compounds, their diverse chemical properties, and their persistence in the environment for decades without degradation raise alarms at a broader societal level ¹¹. The range of potential health concerns associated with PFAS is notably wider than that for dioxins and PCBs ¹².

The development of toxic equivalency factors (TEFs) for PFAS could enhance the public's understanding of these complexities. TEFs for dioxins and dioxin-like compounds have significantly improved the precision of health and ecological risk assessments, supporting regulatory decisions regarding the exposures and sources that present the most significant risks ¹³. A similar approach applied to PFAS and PFAS mixtures could yield comparable benefits ¹⁴.

Site Investigation

Currently, the inconsistent quality of PFAS contamination data complicates the process of extrapolating PFAS contamination conditions and results from one location to another. Research shows that many sites thought to be contaminated lack high-quality testing data, especially in areas near known sources such as firefighting foam discharge locations and specific industrial facilities ¹⁵. These same challenges continue to impact dioxin and PCB site investigations as well, leading to data and knowledge gaps that misguide remediation efforts and policy decisions.

Enhancing analytical testing is not the only solution. New geospatial methods and advancements in supervised data learning tools to optimize environmental data sets for identifying critical source areas and contaminants will strengthen public health protections and remediation strategies ¹⁶.

Footnotes

1. George and Birnbaum. (2024), https://doi.org/10.1289/EHP14449.
2. Simon et al. (2019), https://doi.org/10.1002/rem.21624.
3. Rehman et al. (2023), https://doi.org/10.1016/j.teac.2023.e00198 ; Guelfo et al. (2021), https://doi.org/10.1002/etc.5182.
4. Fiedler et al. (2022), https://doi.org/10.1016/j.chemosphere.2021.132449.
5. Bartlett and Davis (2018), https://doi.org/10.1002/rem.21549.
6. Wanzek et al. (2024), https://doi.org/10.1111/gwmr.12669.
7. Fernández-González et al. (2015), https://doi.org/10.1080/10408398.2012.710279 ; Zennegg. (2018), https://doi.org/10.2533/chimia.2018.690.
8. Patlewicz et al. (2019), https://doi.org/10.1289/ehp4555.
9. Burkhard and Votava. (2022), https://doi.org/10.1002/etc.5526.
10. White and Birnbaum. (2009), https://doi.org/10.1080/10590500903310047.
11. Abunada et al. (2020), https://doi.org/10.3390/w12123590.
12. George and Birnbaum. (2024), https://doi.org/10.1289/EHP14449.
13. DeVito et al. (2024), https://doi.org/10.1016/j.yrtph.2023.105525.
14. Goodrum et al. (2021), https://doi.org/10.1093/toxsci/kfaa123.
15. Salvatore et al. (2022), https://doi.org/10.1021/acs.estlett.2c00502; Cordner et al. (2024), https://doi.org/10.1021/acs.est.3c09746.
16. DeLuca et al. (2023), https://doi.org/10.1021/acs.est.3c03670 ; Dong et al. (2023), https://doi.org/10.1021/acsestwater.3c00134.