PFAS are persistent synthetic chemicals that accumulate in soil, water, and in tissues of organisms. These compounds have been shown to travel through food webs and may disrupt aquatic and terrestrial ecosystems. Scientists are working to better understand their movement, persistence, and risks to ecological health.
Understanding PFAS and Their Ecological Impacts
My colleagues have addressed several topics relevant to environmental PFAS, including developing and changing PFAS regulations, techniques for monitoring PFAS in the air, and the recently updated PFAS drinking water standards. Some scientific studies have indicated that direct exposure to certain PFAS compounds can impact ecological communities (U.S. Environmental Protection Agency Office of Water, 2024). Additionally, indirect impacts have been observed as a result of these persistent chemicals accumulating in the environment and the tissues of living organisms (Prosser et al., 2015; Kelly et al., 2024).
The ecological impacts and potential human health risks of PFAS were also discussed in the United States Environmental Protection Agency’s (EPA) PFAS Strategic Roadmap: 2021 – 2024, with a greater focus given to human health impacts than environmental or ecological effects. As the roadmap notes, further research is needed to understand the ecological impacts of PFAS and develop effective mitigation strategies. In the interim, available testing methods can be used to assess the bioaccumulation potential of different PFAS compounds and evaluate potential ecological risks.
The History and Persistence of PFAS
The term ‘PFAS’ covers a class of man-made chemical compounds first invented in 1938 and used starting in the 1940s for their water-, flame-, oil-, and grease-repellent properties. A notable application was in the production of Teflon™ coating on pots and pans. Today, more than 6,500 PFAS compounds are believed to be in the environment, including in remote areas such as the Arctic Circle. The chemical bond between the fluorine and carbon of the PFAS compound is one of the strongest chemical bonds due to the electronegativity differences between these elements. The strength of this bond lets PFAS compounds persist in the environment longer than other chemicals, with some studies estimating that some of these compounds will last for thousands of years (Kwiatkowski et al., 2020).
How PFAS Move Through the Environment
PFAS emissions can be released into the air, water, and through waste management processes, subsequently accumulating in soils and migrating into aquatic and ecological systems over time. They also have the potential to bioaccumulate in living organisms, including plants, shellfish, and large mammals. Bioaccumulation is a process through which environmental contaminants tend to more substantially impact certain categories of animals—i.e., those that occupy niches high in the food web (predators) or have exceptional lifespans (e.g., turtles, sharks) are impacted more than species that occupy low niches in the food web (prey, plants, microbes) or are short-lived. Bioaccumulation is the process that causes mercury, for example, to be a contaminant of concern for consumers of swordfish, which is a long-lived, predator animal. While bioaccumulation of PFAS is recognized to occur (Ahrens and Bundschuh, 2014), less is known about its associated risks to impacted species.
Detecting PFAS in Environmental Samples
The EPA has published a number of methods for detecting PFAS in environmental samples. EPA Method 1633 can quantify 40 PFAS compounds in wastewater, surface water, groundwater, soil, biosolids, sediment, and tissues. However, 40 compounds represent a small fraction of the more-than-6,500 known PFAS compounds, and more information is needed. To begin closing this information gap, EPA Method 1621 was developed as a screening tool to detect compounds containing carbon-fluorine bonds, including PFAS and other species. As such, Method 1621 results represent the maximum plausible extent to which unidentified PFAS species may be present. However, these are overestimates since the results include some non-PFAS species as well. When interpreted together, Methods 1633 and 1621 deliver some insight about what is specifically quantifiable relative to what may yet be unknown about the presence of PFAS in an environmental system.
PFAS Bioaccumulation Testing and Evaluation
As mentioned above, PFAS compounds are persistent in the environment and can bioaccumulate in the tissues of organisms. Empirical bioaccumulation testing can be performed to better understand these processes. Our laboratory in Port Gamble, WA, has been performing bioaccumulation testing with marine, freshwater, and terrestrial test organisms since its inception in 2004.
The results of these bioaccumulation studies can be used to calculate bioaccumulation factors, which shed light on the availability from the sample. These results can then be applied in trophic models to predict the exposures of other organisms living at the same site. A risk quotient can also be calculated, usually by dividing the environmental concentration of PFAS by a predicted no-effect concentration (when available). When the resulting ratio is greater than 1, it suggests that the PFAS concentration may exceed levels considered to cause no effect, indicating that further evaluation may be necessary.
In 2024, EPA released aquatic life criteria for 10 PFAS compounds. These criteria, established under the Clean Water Act, put forth environmental concentrations of PFAS that are considered protective of aquatic life. States and Tribes can use this information to establish water quality standards in their jurisdictions. These values, expressed as both water column and tissue concentrations, can also be used to evaluate potential risks.
Key Takeaways on PFAS Ecological Risk
- PFAS persist in soil, water, and biological tissues, and can bioaccumulate through food webs.
- Detection relies primarily on EPA Methods 1633 and 1621, which provide complementary insights.
- Aquatic-life criteria now exist for ten PFAS compounds under the Clean Water Act.
- Understanding ecological risk requires assessing concentration, exposure duration, and organism sensitivity.
As with any contaminant, it is important to understand the potential ecological risk of PFAS in the environment. For a compound to pose an ecological risk, that compound has to react with an appropriate receptor site of an organism, have a high enough concentration to do so, and have sufficient contact time to elicit an effect. Laboratory studies can help better understand the relationship between the environmental sample concentrations and potential ecological effects.
About the Author
Jay Word is a Project Manager at Spheros Environmental with over 20 years of experience in marine, estuarine and freshwater toxicology and ecological evaluations, remedial investigations, and scientific sampling. He has held lead roles in numerous freshwater and marine studies. Mr. Word has developed changes to test methodologies for the Puget Sound Estuary Protocols, and has been involved in a variety of projects ranging from bioassay testing conducted following specific protocols to more creative research-oriented programs. He is proficient in performing, conducting analysis, and reporting for toxicity tests of water and sediments using invertebrates and fish. Mr. Word has collected samples from Brazil to the American Arctic and many ports and waterways in between. Mr. Word has also performed taxonomic identifications and conducted multivariate analysis on many benthic communities.