What Are "Forever Chemicals" and How Do We Deal With Them?

Perfluoroalkyl and polyfluoroalkyl substances, or PFAS, were first discovered in the mid-20^th century¹ and were quickly adopted by product manufacturers looking to develop new waterproof materials and non-stick coatings for cookware. Following a deadly fire onboard a U.S. naval aircraft carrier,² PFAS came to the rescue once again; scientists were able to develop a new PFAS-containing aqueous film-forming foam (AFFF) that was an exceptionally effective fire retardant.

The extreme chemical stability of PFAS is key to their utility, but this unfortunately also makes them a troublesome class of long-lasting environmental contaminant, which can be spread around the globe easily without breaking down. Nicknamed the “forever chemicals”, traces of PFAS have recently been discovered in the most remote regions of Antarctica³ and in the blood of people and animals worldwide.⁴

Yet, despite their blanket environmental presence, still relatively little is known about the risks of PFAS contamination and how to control it. Identifying PFAS of concern, detecting their presence in nature and eventually removing these contaminants are all key research priorities for today’s environmental engineers.

Identifying PFAS and their potential dangers

According to the U.S. Environmental Protection Agency,⁵ exposure to PFAS in high quantities may lead to reproductive issues in pregnant women, adverse developmental effects in young children and an increased risk of developing prostate, kidney and testicular cancers.

But studying the health effects of PFAS is a surprisingly difficult endeavor. In order to assess the risk that these PFAS contaminants may present to human and animal health properly, scientists first need to know exactly what PFAS are present in the environment and in what concentrations. Unfortunately, the answers to such questions are far from straightforward.

“Those compounds that occur at the highest concentration may not be the most relevant in terms of, say, risk to ecosystem services or humans,” commented Jens Blotevogel, PhD, research assistant professor in the Department of Civil and Environmental Engineering at Colorado State University,. “It may be hidden somewhere in these lower concentration species, and then there are transformations happening among PFAS too.”

Dr. Blotevogel is one of a team of researchers looking to unravel the complexities of PFAS. Using the 21 tesla Fourier-transform-ion cyclotron resonance mass spectrometer (21T FT-ICR MS) at the National High Magnetic Field Lab, Blotevogel and his colleagues have developed a new technique that is able to identify tens of thousands of PFAS from a single environmental sample.⁶

“The FT-ICR MS is the instrument with the highest mass resolution in the world,” Blotevogel explained. “So, we were able to resolve peaks in the mass spectrum that no other instrument would be able to resolve, meaning we can see species that you can’t see on any other instrument and tell them apart.”

The research team is currently working to build a PFAS library using this data, so that other researchers and government departments can utilize the detailed information gathered on these PFAS via 21T FT-ICR MS.

“We want to develop a PFAS library that expands the current library available and develop tools for forensic analysis,” Blotevogel continued. “Ultimately, because not everyone has an FT-ICR MS in the basement, we want to identify important marker compounds that could be source- and product-specific markers for forensics.”

“That could be [identifying] molecules of interest for risk and toxicity or transport-based studies so that they hopefully could then be synthesized by producers. They could then be analyzed on lower resolution mass spectrometers, such as a tandem mass spectrometer, for instance.”

So far, the team has studied the PFAS present in firefighting AFFFs and in natural organic matter, with plans to study PFAS presence in groundwater in the future.

PFAS Testing: Overcoming Challenges and Meeting Regulatory Requirements

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Early detection can curb environmental risk

The only real way to prevent PFAS from entering the food chain and becoming a potential health risk is to minimize or remove these chemicals from the environment. However, testing a site for possible PFAS contamination currently requires samples to be sent away to off-site laboratories for chemical analysis — a process that can be costly and time consuming.

Researchers at Curtin University, Australia, in collaboration with Universidad Nacional de Córdoba, Argentina, recently developed a new on-site testing method⁷ that can near-immediately detect and quantify the levels of common PFAS in water samples. Published in the journal Analyst, the researchers demonstrate the application of the technique in detecting and quantifying perfluorooctanesulfonate (PFOS⁻), one of the more prominent emerging PFAS contaminants, in spiked drinking water and seawater samples.

“Our method is based on electrochemistry, specifically voltammetry, which is a method that allows us to control the voltage applied between electrodes and measure the current,” Professor Damien Arrigan of Curtin University explained. “The magnitude of the current gives us an indication of the concentration of a substance.”

The method uses these electrodes to push ionized PFOS⁻ across an immiscible oil–water boundary, using special glass membranes that contain microholes. The movement of PFOS⁻ ions changes the electrical properties of the oil–water interface, which can be analyzed and used to quantify even very low concentrations of PFOS⁻ in a sample.

“We essentially collect all the PFOS⁻ together in the oil phase in a very small volume. We can build up a relatively high concentration in the oil phase, and then push it back across the interface, giving us a current that is proportional to the concentration,” Arrigan explained.

One of the strengths of this method is that it is very flexible. The technique can be applied to most common PFAS compounds with minimal changes being made to the testing apparatus.

“The limitation of our approach is that the PFAS substances must be ionized or ionizable, so they must be charged in solution,” Arrigan said. “There are some PFAS-replacement compounds that have come in in the last few years that are actually neutral, so we can't detect those.”

With further development and commercialization, the researchers believe that this technique can be made into a portable, robust testing solution for the environmental industry. Government agencies could also make use of such a testing solution to survey PFAS levels in the environment quickly and mark areas that may need remediation.

Improved Throughput for the Analysis of PFAS in Drinking Water

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Removing PFAS from our water

The stability of PFAS makes them a particularly tricky class of compounds to remediate, even if the contaminant’s presence can be detected and identified quickly. Many of the most common environmental cleanup technologies, such as chemical oxidation or bioremediation, are largely ineffective at addressing PFAS.⁸

Current remediation technologies available to treat PFAS contamination in water normally rely on adsorption or ion-exchange mechanisms. For example, granulated activated carbon has previously been shown to be an effective sorbent media for removing long-chain PFAS from water.⁹ However, short-chain PFAS have remained difficult to deal with.

Recently, scientists from the University of North Carolina at Chapel Hill reported the development of a new filtration resin that is able to capture both long- and short-chain PFAS.¹⁰ The resin—an ionic fluorogel—contains a fluoronous component that helps to attract PFAS to the resin, as well as an ionic component that initiates ion exchange to collect the PFAS and keep them held in the resin.

Additionally, unlike other filtration resins that may become less effective over time, this new ionic fluorogel resin can be washed with a simple methanol solution and reused multiple times.

In water spiked with 21 common PFAS seen in North Carolina, the ionic fluorogel resin was able to remove around 85% of all PFAS, including 100% of the troublesome PFOS and perfluorooctanoic acid (PFOA), as well as 70 to 80% of short-chain PFAS.

Such a resin is not dramatically different from other filtration resins used for non-PFAS contaminants in water, and so the researchers are hopeful that with adequate funding this technology could become commercially implemented within the next five years.

While there are efforts being made to phase out PFAS¹¹ and reduce the number of PFAS-containing products circulating in the market, the long-lasting nature of these compounds means that PFAS contamination will likely continue to be an environmental concern for years to come. But with the advent of new detection, analysis and treatment options, this modern problem is well on the way to finding its modern solution.

References

1. Interstate Technology Regulatory Council. History and user of per- and polyfluoroalkyl substances (PFAS). https://pfas-1.itrcweb.org/fact_sheets_page/PFAS_Fact_Sheet_History_and_Use_April2020.pdf. Published April 2020. Accessed April 2022. 

2. Vergun D. Naval research lab chemists search for PFAS-free firefighting foam. U.S. Department of Defense. https://www.defense.gov/News/News-Stories/Article/Article/2017249/naval-research-lab-chemists-search-for-pfas-free-firefighting-foam/. Published November 15, 2019. Accessed April 2022.

3. Greenpeace. Microplastics and persistent fluorinated chemicals in the Antarctic. https://www.greenpeace.org/static/planet4-international-stateless/2018/06/4f99ea57-microplastic-antarctic-report-final.pdf. Published 2018. Accessed April 2022.

4. PFAS in the US population. Agency for Toxic Substances and Disease Registry. https://www.atsdr.cdc.gov/pfas/health-effects/us-population.html. Published June 24, 2020. Accessed April 2022.

5. Our current understanding of the human health and environmental Risks of PFAS. U.S. Environmental Protection Agency. https://www.epa.gov/pfas/our-current-understanding-human-health-and-environmental-risks-pfas. Published October 14, 2021. Accessed April 2022.

6. Young RB, Pica NE, Sharifan H, et al. PFAS analysis with ultrahigh resolution 21T FT-ICR MS: Suspect and nontargeted screening with unrivaled mass resolving power and accuracy. Environ Sci Technol. 2022;56(4):2455-2465. doi: 10.1021/acs.est.1c08143

7. Viada BN, Yudi LM, Arrigan DWM. Detection of perfluorooctane sulfonate by ion-transfer stripping voltammetry at an array of microinterfaces between two immiscible electrolyte solutions. Analyst. 2020;145(17):5776-5786. doi: 10.1039/d0an00884b

8. Treatment Technologies – PFAS — Per- and Polyfluoroalkyl Substances. https://pfas-1.itrcweb.org/12-treatment-technologies/. Updated August 2021. Accessed April 2022.

9. Ochoa-Herrera V, Sierra-Alvarez R. Removal of perfluorinated surfactants by sorption onto granular activated carbon, zeolite and sludge. Chemosphere. 2008;72(10):1588-1593. doi: 10.1016/j.chemosphere.2008.04.029

10. Kumarasamy E, Manning IM, Collins LB, Coronell O, Leibfarth FA. Ionic Fluorogels for remediation of per- and polyfluorinated alkyl substances from water. ACS Cent Sci. 2020;6(4):487-492. doi: 10.1021/acscentsci.9b01224

11. What are PFAS chemicals?. Environmental Working Group. https://www.ewg.org/what-are-pfas-chemicals. Accessed April 2022.