Theme: 07. Per- and Polyfluorinated Alkyl Substances (PFAS)

Topic Area: 7l. PFAS Human Health and Ecological Risk Assessment and Toxicity

Formatted Title:

Detecting PFAS Human Serum: Testing beyond Legacy PFAS

Background/Objectives:

Per- and polyfluoroalkyl substances (PFAS) are a family of compounds and although the exact number is unknown, it is estimated that there may be >5000 unique PFAS in the environment. In the summer of 2022, National Academies of Science provided guidance on PFAS exposure, testing and clinical follow up, however, actions were limited due to cost and awareness of resources. Because they are so ubiquitous, it is estimated that >97% of people in the United States have PFAS in their blood. The major routes of exposure for the general population are through contaminated drinking water, food, personal care products and indoor dust. However, workers who manufacture products containing PFAS or work at or near fire training facilities have higher risk for PFAS exposure. Currently the only known way to rapidly reduce levels of PFAS in the body are plasma and blood donation. PFAS testing is additionally limited by the availability of standards, however there are numerous precursor-PFAS that can transform into legacy PFAS, thus leading to increasing body burden even after exposure has concluded. The objective of this study was to analyze samples of pooled human serum, serum standard reference material (NIST SRM 1957) and aqueous film foaming foam (AFFF) by gas chromatography (GC)-Orbitrap high resolution mass spectrometry (HRMS) and liquid chromatography (LC)-Orbitrap-HRMS for targeted quantitative analysis and qualitative non-targeted analysis.

Approach/Activities:

Human serum samples from an impacted community were pooled and extracted for PFAS. Pooled samples were split onto a GC-Orbitrap-HRMS and LC-Orbitrap-HRMS and analyzed. Twelve (12) PFAS standards were used on the GC-Orbitrap for quantitative analysis of volatile PFAS. Volatile PFAS such as FTOH and FASAs are known to transform into legacy PFAS once they are in the body. Seventy (70) PFAS standards were run on the LC-Orbitrap for quantitative analysis of legacy and precursor PFAS. Quantitation was performed using the parent ion. PFAS spectral libraries provided by Thermo Fisher Scientific and NIST were used for additional compound identification. Standards, when available, were used to determine predictable retention times for non-target hits. Finally, AFFF was analyzed in order to acquire additional spectral information on suspect hits and provide evidence of a potential source of precursor-PFAS. All non-targeted analyses were performed in Thermo Fisher Scientific software CompoundDiscoverer and the quantitative analysis was performed in TraceFinder.

Results/Lessons Learned:

Reporting limits of PFASs analyzed by LC-Orbitrap-MS ranged from 0.05 to 2 ppb and by GC-Orbitrap-HRMS reporting limits were 10 ppb. Quantitative results for NIST SRM 1957 were within 20% of the published results. PFOS, PFHxS, and PFOA were the major constituents in both SRM 1957 and the pool serum samples from the impacted community. Although results from non-targeted analysis of PFAS in serum are qualitative, results can still be used to assess the overall body burden. PFOS in serum was > 20 ng/mL, which the National Academies of Science considers a high exposure range, and the guidance encourages reducing the risk of exposure and increasing medical screening for lipids and cancers. The use of HRMS to determine the body burden of PFAS demonstrates that PFAS-impacted communities are exposed to a complex mixture of PFAS that may transform in the body after exposure.

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Mike Hauer