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PFAS Sampling: An Introduction to Methods, Challenges, and Best Practices BY RAUL DOMINGUEZ, KIMLEY-HORN & ASSOCIATES, INC. & AMLAN GHOSH, CORONA ENVIRONMENTAL CONSULTING, LLC. texas section awwa’s water science & research division
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er- and polyfluoroalkyl substances (PFAS) are a large family of synthetic man-made compounds that contain fluorine in their carbon backbone. Perfluorinated compounds have all their carbons completely fluorinated, whereas in Polyfluorinated compounds some of the carbons are incompletely fluorinated. The polyfluorinated compounds are susceptible to a certain amount of biotransformation in the environment, and they tend to transform into dead end perfluorinated chemicals that degrade at an extremely slow rate. Figure 1 illustrates the diversity of compounds that belong to the PFAS family tree. They have been widely used in industrial and consumer products because of their unique chemical and physical properties. These include resistance to water, stains, grease, oils, and temperature fluctuations.
Figure 1. Family Tree of Per- and Polyfluoroalkyl Compounds1.
PFAS can be classified into two groups: long chain (≥6) and short chain (<6). PFAS are extremely resistant to biodegradation and breakdown due to their exceptional chemical stability. There is a belief that the longer the carbon chain, the greater the persistence and bioaccumulation in the environment8. Their chemical properties enable them to migrate easily between matrices and concentrate in the soil, surface water, groundwater, air, breast milk, food, among others4. As a result, 95-99% of the U.S. population has measurable concentration of some PFAS in their blood2. An analysis by the Environmental Working Group estimates that water supplies for 110 million Americans (about one third of the population) may be contaminated with PFAS to different extents3. Perfluorooctanoic acid (PFOA) and Perfluorooctane sulfonic acid (PFOS) are two most common PFAS compounds due to their mass production by industrial facilities such as DuPont and 3M. Extensive toxicology studies on these two compounds strongly indicate that exposure to PFAS results in potential risks to human health. Possible risks include reproductive issues, developmental defects to fetuses during gestation, certain types of cancers, among others. Unfortunately, no federal drinking water standards have been established for PFOA, PFOS, or any PFAS for that matter. The regulatory process was started on February 20, 2020, when the USEPA issued a preliminary regulatory determination to develop drinking water standards for PFOA and PFOS. They are currently gathering public comments and drinking water occurrence data to determine if establishing a maximum contaminant CONTINUED PAGE 25 | pfas
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