Karla Buechler gave a webinar presentation in association with TestAmerica on The Analysis of Polyfluorinated Alkyl Substance (PFAS) Including PFOS and PFOA. Her presentation is summarized in this blogpost.
Polyfluorinated Alkyl Substances (hereinafter referred to as PFASs) are a class of synthetic compounds containing chemicals formed from carbon chains attached to fluorine atoms. As defined, a PFAS must contain at least one fully fluorinated carbon atom. The Carbon-Fluorine bond is one of the strongest bonds in nature due to the short distance between the atoms. PFOS and PFOAs are part of the PFAS subgroup of PFCs denoting they are fully fluorinated. This means all carbons in the backbone have their hydrogens replaced by fluorine. Due to the strength of the Carbon-Fluorine bond, these chemicals are extremely resistant to degradation in the environment. Additionally, these chemicals have a charged functional group attached to one of the carbons at the end of the carbon backbone. This charged functional group is responsible for the molecules “sticky” property, allowing us to attach these molecules to different things for varying uses.
PFASs are released to the environment from manufacturing facilities as well as industries that incorporated PFASs into industrial and consumer products. Production, use and disposal of AFFF (Aqueous Film Forming Foams) such as ones used in fire-fighting foams, are also responsible for the introduction of PFASs to the environment. Secondary sources include secondary facilities that use PFCs in their consumer products that are tossed in the trash and end up in landfills, waste water treatment plants and evaporation into air as air emissions. Environmental exposure pathways can be found in the image below:
Exposure to PFASs can be from occupational exposure due to working with the chemicals or non-occupational (the category most people fall under) through air and food (predominantly fish consumption). Human and wildlife exposure can continue even with the chemicals no longer in use due to their resistance to degradation. PFOS and PFOA (fully fluorinated PFASs) have a half-life in humans ranging from 2 to 9 years (depending on the study). PFOA is associated with liver, pancreatic, testicular and mammary gland tumors in laboratory animals. PFOS is associated with liver and thyroid cancer in rats.
Technology advancements from the 1980s/1990s to the 2000s allowed us to detect levels from parts per million/billion to parts per trillion/quadrillion. We are now able to discover these chemicals in most water bodies in the world. The EPA has utilized these techniques from Liquid Chromatography Mass Spectrometry with two mass analyzers in one instrument (LCMSMS) to develop EPA Method 537 and Method 537 Version 1.1. Methods of manufactures of the chemicals that were adopted by the environmental industry include SW-846 and Method 8321. ASTM published D7979-14 for soils and D7979-15 for a variety of aqueous matrices. None of the mentioned methods have been multi-lab validated making it difficult to receive consistent quantitative results. However, progress is being made regarding methods that yield consistent results.