How PFAS Bioaccumulate in Shellfish and Shorebirds and What it Means for Human Health

By Muhammad OsamaReviewed by Laura ThomsonMar 7 2025

In a recent article published in the Journal of Hazardous Materials, researchers comprehensively explored the presence of unknown per- and polyfluoroalkyl substances (PFAS) in shellfish and shorebirds from the East Asian-Australian Flyway. They aimed to utilize the Total Oxidizable Precursor (TOP) assay to detect and quantify these PFAS precursors, enhancing our understanding of their ecological impact and potential risks to wildlife and human health.

Advancement in PFAS Detection Technology

PFAS are a group of synthetic chemicals widely employed across various industries due to their unique properties, such as water and grease resistance. However, their persistence in the environment and associated health risks have raised significant concerns. Traditional detection methods primarily focus on well-known PFAS compounds, often neglecting unknown precursors that can degrade into harmful perfluoroalkyl acids (PFAAs).

To address this limitation, the TOP assay was developed to convert unknown PFAS precursors into quantifiable PFAAs under controlled conditions. This method enables the semi-quantification of these precursors, offering clearer insights into their presence and potential ecological impacts. While the TOP assay has effectively analyzed samples like sediments and wastewater, its application in biological samples remains limited.

About this Research: Analyzing PFAS

In this paper, the authors analyzed PFAS and their precursors in shellfish collected from the Chinese coast and shorebirds captured in Australia. The aim was to determine the concentrations of various PFAAs, including perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs), before and after applying the TOP assay.

Shellfish samples were collected from mudflats at 11 critical stopover sites along China’s coast during the spring migration seasons of 2018 and 2019. A total of 30 samples, primarily of the Mactra veneriformis, were analyzed. In parallel, blood and liver samples were obtained from three migratory shorebird species in Australia: the bar-tailed godwit (Limosa lapponica), curlew sandpiper (Calidris ferruginea), and red-necked stint (Calidris ruficollis).

Curlew Sandpiper. Image Credit: Voodison328/Shutterstock.com

The researchers adapted the TOP assay to extract and analyze PFAS from biological samples. The process involved controlled oxidation followed by liquid-liquid extraction to isolate PFAAs for quantification using ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Comprehensive quality assurance measures, including procedural blanks and calibration curves, were applied to ensure the accuracy of the results.

Outcomes of Analyzing PFAS in Collected Samples

After applying the TOP assay, the study showed increased PFCA and PFSA concentrations in shellfish and shorebirds. In shellfish, total PFCAs ranged from 0.83 to 75 ng/g (median: 6.5 ng/g) post-assay, compared to less than 0.036 to 28 ng/g before the assay. Notably, increases were observed for perfluoroheptanoic acid (PFHpA) and perfluorooctanoic acid (PFOA), demonstrating the assay’s ability to detect previously unidentified PFAS.

Similarly, in shorebirds, total PFCAs rose significantly. Median concentrations increased from 2.4 to 10 ng/g in red blood cells and from 9 to 33 ng/g in serum. Liver samples exhibited the most dramatic changes, with total PFCAs rising from less than 0.072-126 ng/g (median: 2 ng/g) to 421-8,268 ng/g (median: 3,172 ng/g) post-assay. These findings highlight the potential for PFAS bioaccumulation in migratory shorebirds that consume contaminated shellfish.

Perfluoropentanoic acid (PFPeA) and perfluorohexanoic acid (PFHxA), which were undetectable before the assay, appeared in multiple samples afterward, indicating the presence of unknown precursors that degraded into harmful PFAAs. Interestingly, total PFSAs in liver samples increased from 2.8-312 ng/g pre-assay to 26-313 ng/g post-assay. These results challenge the assumption that the TOP assay converts precursors into PFCAs, showing the complexity of PFAS transformations in biological systems.

Could PFAS Be Detrimental to Biodiversity and Human Health?

This research has significant implications for environmental monitoring and wildlife conservation. The successful application of the TOP assay in biological samples demonstrates its potential as a valuable tool for assessing PFAS contamination across different ecosystems, particularly in regions with suspected exposure. Identifying previously unknown PFAS precursors can inform regulatory policies and management strategies to reduce environmental contamination.

The study emphasizes the need to examine the potential risks of PFAS exposure in wildlife and humans. As migratory shorebirds accumulate PFAS through their diet, the findings raise concerns about human health, particularly for communities that consume shellfish as a dietary staple.

Conclusion: Addressing the Challenge of PFAS Contamination

The TOP assay effectively revealed previously undetected PFAS in shellfish and shorebirds, providing deeper insights into these contaminants' ecological and health implications. The authors emphasized the urgent need for comprehensive investigations into the behavior and impact of PFAS precursors in biological systems.

As awareness of PFAS contamination grows, further research is essential to identify sources, pathways, and long-term effects on the environment and human populations. These findings highlight the importance of enhanced monitoring efforts and the development of strategies to reduce PFAS exposure in wildlife and humans.

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