The class of per- and polyfluoroalkyl substances, short PFAS, is a large class of thousands of chemicals that can be separated into polymers and nonpolymers1. Nonpolymeric PFAS are small, highly mobile molecules like perfluorooctanoic acid (PFOA) that are known to be persistent and can accumulate in the environment and in living organisms. Fluoropolymers are a distinct subset of polymeric PFAS, based on a carbon-only polymer backbone with F atoms directly attached to it. They are known for their exceptional durability, thermal stability, and low-friction, non-stick properties. A well-known example is polytetrafluoroethylene (PTFE), sold under the brand name Teflon.
A Shift in Industrial Processing Aids
There is no sufficient evidence to consider fluoropolymers as being of low concern for environmental and human health2, partly due to the emission of small-molecule PFAS associated with their production. Fluoropolymer manufacturers have replaced the legacy processing aid PFOA with new per- and polyfluoroalkylether carboxylic acids. These new chemicals, such as HFPO-DA (hexafluoropropylene oxide dimer acid) have a shorter chemical chain and a different structure, leading to lower bioaccumulation potential in the human body. Nevertheless they have similar properties to PFOA, including resistance to breakdown and high mobility. HFPO-DA still raises environmental concerns as it has been found in surface water, groundwater, and drinking water in areas where it is produced.
Measuring the Impact of a New PFAS Abatement System
Fluoropolymer production plants have invested in abatement systems to curtail the emission of PFAS but their efficacy has not been reported in peer-reviewed literature. Researchers from Stockholm University measured the concentrations of HFPO-DA and other PFAS in airborne particulates 25 km downwind of a fluoropolymer production plant in Dordrecht, the Netherlands3. The 20-week sampling campaign was strategically timed to capture air quality before, during, and after the installation of a new activated carbon-based abatement system. The data was combined with meteorological information like wind speed and direction to validate the measurements and assess the local and long-range impact of the emissions.
Drastic Reduction in HFPO-DA Emissions
The results provided clear evidence of the abatement system’s success. Before the system was fully operational, HFPO-DA levels reached a maximum of 98.66 pg m⁻³ when the wind came from the direction of the plant. After the system’s implementation, the maximum detected concentration dropped to 12.21 pg m⁻³. The mean measured concentrations decreased by 89%.
The Role of SIRIUS in Uncovering a Complex PFAS Emission Profile
Beyond the targeted analysis of known processing aids, the team also employed a “suspect screening” approach to search for other potential PFAS emitted from the plant. The workflow involved UHPLC-high resolution mass spectrometry (HRMS) with data-dependent MS2 fragmentation. Using SIRIUS, they detected a homologous series of suspected PTFE polymerization byproducts identified as hydrogen-substituted perfluoroalkyl carboxylic acids (H-PFCAs). This series included at least seven homologues (from H-PFHxA to H-PFDoDA). The identities of three of these H-PFCAs were confirmed by acquiring authentic standards and reanalysing the samples. Air concentrations of these newly identified H-PFCAs peaked in the same samples that showed high levels of the known processing aid HFPO-DA, suggesting they were released from the same source—the fluoropolymer plant.
Finding Molecular Families in Complex Samples with SIRIUS
In SIRIUS 6, the Homologous Series view helps you quickly find groups of related molecules within your complex samples using a Kendrick Mass Defect (KMD) plot. This plot helps identify groups of molecules that share a common structural backbone but differ by a consistent repeating unit, such as a CH2 group. The KMD plot works by transforming mass data to the Kendrick mass scale, where the mass of the repeating unit is an integer. The KMD is then calculated as the difference between the exact Kendrick mass and its nominal (integer) mass. When plotted against the nominal Kendrick mass, molecules of the same homologous series align horizontally, as they share a very similar KMD. This alignment makes it easy to spot these molecular families. SIRIUS allows you to select a specific repeating unit to define the series you wish to visualize.
Implications for Environmental Monitoring
This study provides evidence that investment in abatement technology can be highly effective in reducing emissions of fluorinated processing aids. It also demonstrates that fluoropolymer production plants emit a complex mixture of PFAS, including polymerization byproducts that may be overlooked in routine targeted monitoring programmes. The successful identification of H-PFCAs highlights the power of combining high-resolution mass spectrometry with advanced computational tools like SIRIUS. Non-targeted and suspect screening approaches are crucial for developing a comprehensive understanding of industrial emissions and their impact on the environment.
References
- Buck RC, Franklin J, Berger U, Conder JM, Cousins IT, de Voogt P, Jensen AA, Kannan K, Mabury SA, van Leeuwen SP. Perfluoroalkyl and polyfluoroalkyl substances in the environment: terminology, classification, and origins. Integr Environ Assess Manag. 2011 Oct;7(4):513-41. doi: 10.1002/ieam.258. ↩︎
- Lohmann R, Cousins IT, DeWitt JC, Glüge J, Goldenman G, Herzke D, Lindstrom AB, Miller MF, Ng CA, Patton S, Scheringer M, Trier X, Wang Z. Are Fluoropolymers Really of Low Concern for Human and Environmental Health and Separate from Other PFAS? Environ Sci Technol. 2020 Oct 20;54(20):12820-12828. doi: 10.1021/acs.est.0c03244. ↩︎
- Dalmijn J, Shafer JJ, Benskin JP, Salter ME, Johansson JH, Cousins IT. HFPO-DA and Other PFAS in Air Downwind of a Fluoropolymer Production Plant in the Netherlands: Measurements and Modeling. Environ Sci Technol. 2025 May 6;59(17):8662-8672. doi: 10.1021/acs.est.4c13943. ↩︎
