Compostable fast-food containers, designed to be more environmentally friendly than single-use plastic ones, can release toxic per- and polyfluoroalkyl substances (PFAS) into the air, according to an analysis of samples from retailers in Toronto (Environ. Sci. Technol. Lett. 2023, DOI: 10.1021/acs.estlett.2c00926). The results suggest that polymers with fluorinated side chains, which are used to make paper-based food packaging grease resistant, break down over time into volatile fluorotelomer alcohols and fluorotelomer methacrylates.
Researchers screened 42 samples—including molded fiber bowls, burger wrappers, and popcorn bags—for total fluorine content. The molded fiber bowls contained the highest levels. Analysis of eight of the samples revealed up to 14 PFAS in each. The most abundant PFAS in all but one of the eight samples were 6:2 fluorotelomer alcohol and 6:2 fluorotelomer methacrylate.
Surprisingly, total PFAS levels dropped by up to 85% after storing the products for two years, says Marta Venier, an environmental chemist at Indiana University and one of the corresponding authors of the work. The researchers attribute the loss to volatilization of fluorotelomer alcohols and other PFAS.
Packaging manufacturers typically don’t reveal what’s in their products, but Venier and her colleagues have some indication that they contain polymeric PFAS with fluorinated side chains. Their work suggests that the polymeric PFAS degrade to fluorotelomer alcohols and other chemicals. “These fluorotelomer alcohols, in turn, can degrade into carboxylic acids, which are toxic as well,” Venier says.
The US Food and Drug Administration raised safety concerns about 6:2 fluorotelomer alcohol in food packaging in 2020, and several manufacturers subsequently phased out the chemical for such applications. Polymeric PFAS have been promoted as safer alternatives because they are more stable, but the study by Venier and colleagues raises questions about that stability.
The researchers are urging regulators to ban all PFAS, including polymeric PFAS, in food packaging. “For Canadians, it’s particularly important because of the legislation passed to limit the use of single-use plastics in Canada,” says Miriam Diamond, an environmental chemist at the University of Toronto and coauthor on the study. “It’s very reasonable to anticipate that there should be greater use of these paper-based materials” because of that legislation, she says.