Forever chemicals, also known as per- and polyfluoroalkyl substances (PFAS), are pervasive in the environment, and a recent study by the University at Buffalo has revealed intriguing insights into their distribution across the food web. The research, published in the American Chemical Society's Journal of Agriculture and Food Chemistry, highlights the importance of distinguishing between different isomers of PFAS, as their unique molecular structures can lead to varying behaviors and impacts on the environment.
The study analyzed samples of water, fish, and bird eggs, uncovering a fascinating pattern in the distribution of PFOS isomers. While more than half of the PFOS detected in wastewater and supermarket fish were branched isomers, which are spherical and compact, the egg yolks of fish-eating birds revealed a different story. In these bird eggs, nearly 90% of PFOS was linear, an elongated form that tends to bind to proteins and remain in tissues longer.
This finding suggests that as PFOS moves through the food web, from water to fish to birds, its linear isomers become more prevalent. The study's corresponding author, Diana Aga, PhD, emphasizes the significance of this discovery, stating that PFOS isomers can bioaccumulate at different rates and should not be treated as identical. This is a crucial distinction, as it challenges the current U.S. and European regulations that lump all isomers together when measuring PFAS.
To distinguish between different isomers, the researchers employed advanced separation techniques, including cyclic ion mobility spectrometry. This technique separates isomers based on their shape differences, which influence their movement through a tube filled with gas. The study's results showed that benthic fish, which feed on the bottom of water bodies, contained a higher total PFOS concentration and longer-chain PFAS compared to pelagic fish, which live in open waters. This finding suggests that consumers who frequently eat bottom-dwelling species may have a higher exposure to PFAS.
In a separate study, the team identified PFOS isomers in wastewater and bird eggs. The wastewater samples, collected from a municipal treatment facility, had a higher concentration of branched isomers, while the bird eggs, collected from abandoned nests near Buffalo Harbor, contained a significant proportion of linear isomers. These findings provide valuable insights into the environmental fate of PFOS and suggest that linear isomers may persist more as they move through the environment.
The study's authors, including PhD students Mindula Wijayahena and Jenise Paddayuman, emphasize the need to examine the differences in the toxicological effects of PFAS isomers. This could potentially lead to the development of molecules with branched structures, which may have reduced bioaccumulation. As the research progresses, it may be time to reevaluate the regulations surrounding PFAS, considering the unique characteristics of each isomer.
