Characterization of PFAS-Containing Aqueous Film-Forming Foams and Their Thermal Degradation Products: Implication for Human and Environmental Health

Details

• Personal Author:
  Bhandari, Shristi ; Biswas, Kousick ; Bello, Anila ; Ross, M. ; Wang, Chen ; Liu, P. ; HewaSahabanduge, C. ; Stueckle, Todd A. ; Bello, Dhimiter
• Description:
  Background and Purpose: Per- and poly-fluoroalkyl substances (PFAS) have emerged as a major environmental health problem of our time. Aqueous Film-Forming Foams (AFFF) are traditional firefighter foams based on PFAS and a major source of PFAS environmental pollution. The main focus of this study was to analyze the chemical composition and thermal degradation behavior of AFFFs that can influence the fundamental physicochemical properties relevant to human exposures: phase distribution and mobility of contaminants (gas, vapor, nano aerosol, PFAS size distribution); chemical composition (generation of free radicals, chain reactions leading to new species, including fluorinated hydrocarbons, inter-species conversions, generation of HF gas and/or acid), toxic gases (CO, SO2, NOx). These thermal degradation byproducts are biologically relevant to human exposure because they alter lung dosimetry, mode of action, and lung toxicology. Methods: For this study, we constructed an environmental chamber testing platform suitable for characterizing thermal degradation behavior and physico-chemical transformation of common AFFFs under controlled experimental conditions. Six representative AFFF foam samples out of 16 characterized foams were burned using a standardized temperature ramp (25 0C to 800 0C, 10 0C/min) under sufficient O2 conditions (21%). We characterized foam emissions with a suite of instruments that measure nano aerosol properties (size and mass distribution and number concentration, HF gas and aerosols, toxic gases (CO, SO2, NOx), VOCs, ROS (by EPR), and aldehydes, and collected samples for subsequent chemical analysis by LC-MS/MS, NMR, SERs, total F by CIC, and other techniques. Extensive physicochemical characterization of the raw foams (LC-MS/MS, LC- Q-TOF MS, Raman, NMR, ICP-MS, establish a baseline for their input chemical composition, including PFAS content and foam matrix. Both targeted (50 species, LC-ESI-MS/ MS) and untargeted (HR-QTOF-MS/MS) PFAS analysis (against a database of >6k compounds) was completed in raw AFFF foam samples, nano aerosols collected in water impingers, as well as 1hr aged aerosols, and other collection media. Matrix components were quantified using both targeted (20 compounds) and untargeted analysis. Results: Thermal degradation of AFFF foams resulted in exclusive nano aerosol generation with the median particle size of 30-40 nm. Twelve to 26 species/ AFFF were quantified in targeted analyses and 18 to 54 species/AFFF were identified in untargeted analyses of foams and TDPs. PFAS concentrations in foams ranged from 23.03 to 40481.3 µg/g. PFOS, PFOSA, and PFNA were the most abandoned PFAS species in AFFF, while PFBA, PFBS, PFHxA, and PFHxS were also present in significant amounts. Untargeted analysis revealed 18 to 54 different PFAS species in the same AFFFs. New PFAS species were formed due to thermal degradation, with an average of four new species detected in the breakdown products. Additionally, high amounts of ROS were found by EPR in the fresh nano aerosols and the aged one suggesting persistent ROS. Toxic gases such as CO, SO2, and NOx were also generated during the burning of AFFFs in the 1-10 ppm range. High amounts of formaldehyde, acetaldehyde, propionaldehyde, acetone and smaller amounts of higher aldehydes were also formed across all AFFFs. No HF was detected under these TD conditions. F mass balance revealed that targeted analysis could account for 0.4% to 76% of total F, with a median value of 5%. At least 16 matrix components were quantified in AFFF foams and TDPs. Conclusions: Thermal degradation of AFFF containing PFAS results in the formation of nano aerosols, new PFAS species, significant amounts of reactive oxygen species, formaldehyde, acetaldehyde, and toxic gases, which have important implications for environmental and human health. This study provides critical insights into the chemical transformations and emissions resulting from the thermal degradation of PFAS-containing firefighting foams, highlighting the need to expand the safety evaluation of AFFFs and their replacements beyond raw foams and to incorporate additional metrics for exposure and risk assessment of firefighting foams - old and new-to mitigate environmental and health risks. Description provided by NIOSH
• Subjects:
  • Fires
  • Fluorocarbons
  • Hazardous Substances
  • Occupational Health
  • Safety
• Keywords:
  • Per- and polyfluoroalkyl substances; PFAS; Fire extinguishing agents; Thermal effects; Aerosols; Toxic gases; Toxicology
• Source:
  Toxicologist 2025 Mar; 204(S1):245-246
• ISSN:
  1096-6080
• Document Type:
  Text
• Genre:
  Abstract or Summary
• Place as Subject:
  Boston Region OSHA ; Massachusetts ; Philadelphia Region OSHA ; West Virginia
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  HELD - Health Effects Laboratory Division
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  3 pdf pages
• Volume:
  204
• NIOSHTIC Number:
  nn:20071575
• Federal Fiscal Year:
  2025
• NORA Priority Area:
  Manufacturing
• Peer Reviewed:
  False
• Download URL:
  https://stacks.cdc.gov/view/cdc/259350/cdc_259350_DS1.pdf
• File Type:
  [PDF - 301.15 KB]
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:622b1cf7f224e6218f727a36de7f1162721be856e08ccdfa1c156d9cba8f7d7c5d737030ca3020c2807e156cef32ca1c0a72b5fbf1ce0e17dc763589239af3cf