At the very core of understanding PFAS, whether delineating nature and extent, assessing risk, or treating the compounds, is understanding the chemistry of these compounds. PFAS comprises a large class of several thousand synthetic fluorinated compounds with unique chemical and physical properties. The carbon-fluorine chemical bond is the strongest in organic chemistry, making PFAS resistant to degradation and extremely persistent in the environment. PFAS compounds are also surfactants, making them very mobile in water.

PFAS compounds have been used in many applications for over 75 years, ranging from stain-resistant clothing and carpeting to aqueous film forming foam, a fire suppressant. As a result, there are many sources of PFAS contamination including industrial sites, landfills, wastewater treatment plants, areas where biosolids have been spread, and fire training areas.

With improvements in analytical chemistry instrumentation, PFAS can now be detected in areas where it had not been suspected in the past. Analytical methods continue to improve, with detection now possible in the low parts per trillion. Until recently, there had not been a commonly used EPA analytical method for the analysis of PFAS. EPA Methods 533 and 537 could be used for analysis of finished drinking water samples, but they were not designed or approved for use with other matrices. Another EPA method, Method 8327, has known difficulties with reproducibility, which limits its use as a tool for screening environmental samples.