Imagine filling a glass with water, frying an egg on a non-stick pan, or wearing a waterproof jacket. Sounds mundane, but these actions connect you to a hidden crisis—one that’s been quietly unfolding for decades. At the heart of this crisis is a group of synthetic chemicals known as per- and polyfluoroalkyl substances, or PFAS. Often called “forever chemicals” because of their persistent presence in the environment, PFAS have become a ubiquitous part of modern life, but their impact is far from benign.
PFAS—A hidden crisis
PFAS compounds consist of a chain of carbon atoms fully or partially bonded to fluorine atoms, forming one of the strongest bonds in organic chemistry. This makes these compounds incredibly resistant to breaking down. “These are extremely stable compounds; they're hydrophobic, oleophobic, and have a remarkable ability to resist breakdown,” explains Carrie McDonough, PhD, assistant professor of environmental analytical chemistry at Carnegie Mellon University.
Get training in Risk Assessing and Characterizing and earn CEUs.
One of over 25 IACET-accredited courses in the Academy.
Risk Assessing and Characterizing course
Over the decades, these properties have led to the widespread use of PFAS in products designed to make life easier and more convenient. Increased production has unfortunately resulted in unintended consequences. PFAS don’t just stay in the products they’re designed for—they migrate into the environment, contaminating water sources and accumulating in the bodies of animals and humans alike.
"Most of what we know is based on a handful of compounds," notes McDonough. "There are thousands of PFAS, and the health effects of many of these are still unknown, especially when it comes to the mixtures of these chemicals that we're all exposed to daily."
Tracking PFAS—The scavenger hunt
"The first evidence of PFAS in human serum was actually quite a long time ago," McDonough points out. "In 1968, scientists started to see organofluorine in blood, indicating these compounds were already widespread." Unfortunately, the significance of this discovery was lost to the scientific community.
The advent of advanced analytical techniques such as liquid chromatography, and liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) helped researchers accurately identify and measure PFAS in environmental and biological samples. LC-MS/MS has now become the standard for detecting specific PFAS, revealing just how entrenched these chemicals are in our environment.
Widely used for quantifying PFAS concentrations in water, soil, and biological samples, LC-MS/MS provides high sensitivity and accuracy. However, it is time-consuming, expensive, and can require specialized laboratory infrastructure. Other approaches, like high-performance liquid chromatography (HPLC) and ion chromatography (IC), generally require sample pre-treatment steps, such as solid-phase extraction (SPE), to concentrate and purify PFAS from complex matrices. Although effective, these techniques can be labor-intensive and are limited to detecting known PFAS compounds, leaving unidentified substances undetected.
Building a library—The challenges of comprehensive characterization
The more one learns about PFAS, it becomes clear that challenges in fully understanding and managing their impact are far from over. Nevertheless, hope persists, with the emergence of tools such as high-resolution mass spectrometry (HRMS).
HRMS offers the sensitivity and selectivity required to detect trace amounts of known and unknown PFAS in complex samples. Unlike traditional methods, HRMS allows for high mass accuracy with precise identification of compounds, even when standards are unavailable, thus providing a more comprehensive view of exposure. This makes HRMS a critical tool in helping researchers bridge and narrow the knowledge gap that persists in PFAS characterization. HRMS’ non-targeted analysis, coupled with its sensitivity, high-throughput screening and adaptability, makes it an ideal technique to match ever-evolving PFAS characterization needs.1
Key improvements in HRMS include increased mass spectral resolving power and high mass accuracy. The latter enables researchers to predict molecular formulas from spectral peaks while the former helps minimize interferences and reveals minor features. Accompanied by additional advancements such as rapid full-scanning rates at frequencies greater than 1Hz allows for effective online chromatography coupling and high sensitivity. This paves the way for the detection of trace contaminants at extremely low levels, down to femtograms, in full-scan modes.
Commercial HRMS instruments also include time-of-flight, ion-trap mass analyzers, and Fourier-transform ion cyclotron resonance systems further providing researchers with varying levels of resolving power, mass accuracy, and scan rates for PFAS characterization. These developments are crucial for moving beyond the limitations of targeted methods and capturing the full PFAS burden in the tissues and fluids of living organisms.
There are thousands of PFAS, and the health effects of many of these are still unknown, especially when it comes to the mixtures of these chemicals that we're all exposed to daily.
McDonough’s research team has utilized these very features of HRMS to help assess various aqueous film-forming foams and complex mixtures of known and unknown PFAS. "With HRMS, we're able to detect a broader spectrum of PFAS, including those that haven't been identified before," says she says. “HRMS has enabled us to test various relevant exposure mixtures, for which we don’t have analytical standards, allowing us to understand what’s biologically relevant to informed biomonitoring, which is using trace concentrations and often really limited volumes of samples.”
Looking ahead: Addressing the PFAS challenge
The story of PFAS is a cautionary tale of how convenience and industrial progress can lead to unintended and far-reaching consequences. While significant strides have been made in detecting and understanding these chemicals, much work remains. Solutions will require not just advanced scientific techniques but also coordinated regulatory action, public awareness, and innovative approaches to remediation and prevention.
In her research, McDonough explores the various solutions that are in development. Using complex mixtures from commercial products such as aqueous film-forming foams (AFFF) in laboratory models has proven a key strategy in uncovering bioaccumulation mechanisms for novel perfluoroalkyl acids (PFAAs). However, the interpretation of results is complicated by the presence of unknown PFAS and non-PFAS compounds, making it difficult to isolate specific toxicological effects. In vitro data is also challenging to extrapolate to in vivo toxicity, suggesting a cautious approach when drawing conclusions.
Nontarget and surrogate analytical techniques, particularly high-resolution mass spectrometry (HRMS), are essential for identifying novel pre-PFAAs in the absence of analytical standards. These techniques help to characterize unknown precursors in environmental samples, though harmonized systems for reporting PFAS are still needed. Surrogate techniques combined with predictive modeling show promise for improving the accuracy and depth of PFAS detection.
Finally, high-throughput bioanalytical tools offer critical advancements for quickly screening the toxicological impacts of pre-PFAAs. Techniques such as ToxCast assays and high-throughput zebrafish models provide rapid insights, although challenges remain in capturing the full effects of transformation products. In silico models are increasingly useful for predicting molecular interactions, though their findings still require validation through laboratory testing.2
The implementation of HRMS could have a transformative impact on regulatory frameworks as well. As governments and environmental agencies push for stricter PFAS regulations, the ability to detect and monitor these chemicals with greater accuracy will likely lead to more comprehensive environmental assessments. HRMS can also play a crucial role in tracking PFAS fate in various environmental compartments, contributing to more effective remediation strategies. However, the high costs and the complexity of HRMS analyses remain barriers to widespread adoption, especially in smaller laboratories or regulatory agencies with limited resources. Nonetheless, the technology’s expanding capabilities make it a key tool for tackling the challenges associated with the comprehensive characterization of PFAS.3
As you turn on the tap, cook your meals, or put on your favorite raincoat, remember: PFAS are more than just hidden chemicals—they’re a legacy of our modern lifestyle that we’re still struggling to understand and control. The challenge of PFAS may be daunting, but with continued research and commitment, a safer, healthier future is within reach.
References:
1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7584354
