Directly Fluorinated Containers as a Source of Perfluoroalkyl Carboxylic Acid
By Heather D. Whitehead and Graham F. Peasle
Environ. Sci. Technol. Lett.
March 6, 2023
Direct fluorination of plastics is performed to impart chemical resistance via exposure of polyethylene to fluorine gas to produce a fluorine-modified surface layer. Leaching experiments were performed on a directly fluorinated container under various conditions and with different matrices, including foodstuffs. The average sum of per- and polyfluoroalkyl substances (PFAS) concentrations measured from extraction of a fluorinated container was 63.75 ± 13.2 ng/g plastic. Seven-day leaching experiments of fluorinated containers with water, methanol, and acetone produced sums of PFAS concentrations that ranged from 0.99 to 66.92 ng/g plastic. Leaching experiments with food matrices produced sums of PFAS concentrations ranging from 2.66 to 7.19 ng/g plastic. A subset of samples subjected to leaching at elevated temperatures generated sums of PFAS concentrations up to 830% higher. In all experiments, short-chain perfluoroalkyl carboxylic acids (PFCAs) were detected in the highest frequencies and concentrations with analyte concentration decreasing as chain length increased. An estimate for PFAS released into food ranged from 0.77 to 2.68 ng/kg body weight per week, showing ingestion of food stored in these containers could be a significant source of exposure. Based on the large number of applications where directly fluorinated containers find use, the observation of PFAS migration suggests use regulations are warranted, and future studies should explore their fate when disposed or recycled.