As scientists continue to learn more about the actions of chemicals in the environment and the body, the list of hazardous substances that were once widely used in everyday applications continues to grow. Per- and polyfluoroalkyl substances (PFAS) are a notable member of this list. This group of synthetic chemicals, which now includes nearly 5,000 different compounds, skyrocketed in popularity in the 1950s due to the grease, oil, water and heat-resistant properties of many of them. Consequently, PFAS became widely used in resistant coatings on fabrics and carpets, in firefighting foams, cleaning products, paints, food packaging, and cookware to name just a few.
Unfortunately, these substances have downsides in addition to their beneficial properties. Thanks to the strong bonds between the carbon and fluorine atoms that form the basis of PFAS, they can remain intact in the environment, leading to environmental contamination and bioaccumulation in humans and animals. While some members of the PFAS family have been studied thoroughly, this is very much a growing area for research. A number of these substances are less well researched, and the implications of PFAS contamination are not yet fully understood. Monitoring and further research on their modes of action are key to closing these gaps.
To learn more about the hazards posed by PFAS and the detection challenges faced by analysts, we spoke to Craig Butt, Staff Application Scientist in the cannabis, environmental, food and beverage division of SCIEX.
Karen Steward (KS): What is the typical route of entry for PFAS compounds into the human body? How can exposure to high levels of PFAS affect health?
Craig Butt (CB): PFAS exposure is complex and still not completely understood. Drinking water can be a significant exposure source for people living near contaminated sites, such as airports with aqueous film-forming foam (AFFF)-contaminated surface or groundwater. Several studies have shown that higher levels of PFAS in drinking water are associated with higher PFAS serum concentrations, demonstrating the importance of drinking water to PFAS exposure. For the general population, diet and drinking water can be significant sources. Finally, inhalation of dust and the metabolism of PFAS precursors may also be important, but those exposure routes are not well quantified. With respect to health effects, the most substantial evidence suggests an impact on the immune system.
KS: What are the challenges of testing human blood for PFAS? How does mass spectrometry help to overcome these issues?
CB: Ultimately, liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a very specific analysis technique that helps improve confidence in what is being detected. For example, early PFAS research showed the presence of several endogenous compounds in human blood that resulted in false detections. Using LC-MS/MS allows for an extra level of selectivity to eliminate those interferences. Further, increased specificity generally means lower background noise, which enables analysts to detect much lower levels of PFAS.
KS: Which PFAS are the most important to test for in blood?
CB: That is a difficult question… all of them? Mid-range chain-length compounds, meaning 6–12 carbons, appear to be the most bioaccumulative and thus typically have higher blood levels. But the PFAS industry has shifted production to shorter chain-length compounds and while these compounds are less bioaccumulative, it is important to understand if their presence is increasing in humans. In addition, it is also important to monitor other replacement PFAS chemicals, such as perfluorinated ether acids, to ensure that these novel compounds are not bioaccumulating.
KS: Are there other ways to monitor for PFAS exposure, such as urine testing?
CB: PFAS accumulate in the body’s protein-rich tissues – such as blood, kidneys and the liver – and can stay in the body for several years. PFAS behave much differently from traditional chlorinated and brominated contaminants, which accumulate in fatty tissues. Urine does not appear to be a good medium for monitoring PFAS body burdens. Previous studies show that only short-chain compounds, such as pentafluorobenzoic acid (PFBA), are detected in urine. Further, when PFAS is detected in urine, the levels are very low, making it difficult to measure with confidence. Alternatively, breast milk appears to be a good biomonitoring tissue and can provide information on early-life exposure to developing children.
KS: Do you foresee changes to PFAS regulations? How can testing labs stay ahead?
CB: Absolutely. The types of PFAS being manufactured and our knowledge of human exposure have changed drastically over time, and the scientific and regulatory communities have adapted accordingly. For example, the early 2000s saw a shift away from the manufacture of perfluorooctane sulfonate (PFOS) in most parts of the world, and in the late 2000s, there was a global movement to cease the production of perfluorooctanoic acid (PFOA) and longer-chain perfluorinated carboxylic acids. However, in the mid-2010s, we became aware that novel perfluorinated ether acids, such as GenX, were in the environment and several were subsequently detected in human blood. In addition, as our knowledge about the long-term health effects of PFAS improves, I anticipate that regulatory levels will change (presumably to be more protective). Further, I expect that we will see regulatory limits for additional exposure sources such as food and soil.
Most importantly, total organic fluorine analysis shows us that our targeted screening approaches are only capturing a small fraction of the fluorinated compounds in our bodies. Analytical chemists are very good detectives and they are continually finding new PFAS compounds in humans, wildlife and the environment. Regulations will presumably adapt as novel PFAS are found. To truly get ahead of the curve, labs can incorporate non-target screening methods to look for “unknown” PFAS or those that are not yet reported.
Finally, it is important to have a robust and comprehensive analytical method. Robust implies the ability to analyze large numbers of samples and dirty matrixes, such as fatty foods and soil. With respect to comprehensive methods, labs should be able to analyze the entire suite of PFAS, ranging from very short, polar PFAS to long-chain, hydrophobic PFAS.
Craig Butt was speaking to Dr Karen Steward, Senior Science Writer for Technology Networks.