Forever chemicals – they're everywhere, and a new study reveals a surprising twist in how these persistent pollutants behave in our environment. This research, conducted by University at Buffalo chemists, dives deep into the world of per- and polyfluoroalkyl substances (PFAS), also known as "forever chemicals," and how their different forms, or isomers, move through the food web. Let's explore this fascinating and important topic.
First things first: what are PFAS? These are synthetic chemicals used in countless products, from nonstick cookware to firefighting foam. They're called "forever chemicals" because they don't break down easily, persisting in the environment and potentially harming our health.
But here's where it gets intriguing. The study, published on December 2, 2025, focused on a specific PFAS called perfluorooctanesulfonic acid (PFOS), once a common ingredient in many products. The researchers analyzed samples of water, fish, and bird eggs and found that PFOS appeared in different structural forms – isomers – depending on the sample.
Think of isomers like different LEGO arrangements using the same bricks. They have the same chemical formula but different shapes, which affects how they behave. For instance, in wastewater and supermarket fish, the researchers found that more than half of the PFOS were branched isomers, which are compact and dissolve more readily in water. However, in the egg yolks of fish-eating birds, nearly 90% of the PFOS was linear, an elongated form that tends to bind to proteins and remain in tissues longer.
"Taken together, these results suggest that as PFOS moves across the food web — from water to fish to birds — its linear isomers become more prevalent than branched isomers," explains Dr. Diana Aga, the study's corresponding author.
And this is the part most people miss... The study highlights a crucial point: existing regulations often treat all PFAS isomers as the same, but this research shows they don't behave the same way. The different shapes of isomers can lead to different levels of bioaccumulation, meaning they build up in living organisms at varying rates.
So, how do scientists tell these isomers apart? They use a technique called cyclic ion mobility spectrometry. Imagine two sheets of paper – one flat and one crumpled into a ball. If you drop them, the crumpled one will hit the ground first. This technique separates isomers based on their shape, allowing researchers to measure how quickly they move through a tube filled with gas.
The team analyzed PFAS in seven unfrozen supermarket fish samples, including both bottom-dwelling (benthic) fish like cod and pelagic fish that live in open waters like salmon. The results, published in the Journal of Agriculture and Food Chemistry, revealed that benthic fish generally had higher concentrations of PFOS and more types of branched isomers compared to pelagic fish. These bottom-dwelling fish also had higher proportions of longer-chain PFAS, such as perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA).
"These results suggest that consumers who frequently eat bottom-dwelling species may have a higher exposure to PFAS," says Mindula Wijayahena, a PhD student and first author of the study.
In a separate study published in the Journal of the American Society for Mass Spectrometry, the team analyzed PFOS isomers in wastewater and the egg yolks of double-crested cormorants, a type of fish-eating bird. While the wastewater contained more branched isomers, the egg yolks were overwhelmingly linear.
"Although we know linear isomers tend to accumulate more in tissue than branched, the reason why the eggs skewed so heavily to linear warrants further investigation," says PhD student Jenise Paddayuman, the first author of this study.
Controversy alert! The research suggests that we may need to rethink how we regulate PFAS. If certain isomers are less harmful or don't accumulate as much, should we consider designing new molecules with those specific structures? This opens up a fascinating debate about the future of chemical design and environmental protection.
What are your thoughts? Do you think current regulations are sufficient, or do we need to consider the different behaviors of PFAS isomers? Share your opinions in the comments below! This research was supported by the U.S. National Science Foundation and the Environmental Protection Agency.
