When it comes to evaluating the ways that PFAS can harm living organisms, there’s no simple way to start. There are often more questions than answers, followed by a series of decisions that must be made to make sure you’re limiting any sort of bias, contamination, or overly convoluted conclusions. As such, scientists are always looking for a way to simplify processes.
Enter the mobile fish lab. The mobile fish lab brings the experimental setup of a scientific laboratory you’d find on a university campus to the field. In this study, a team led by STEEP scientists used the mobile fish lab to expose fathead minnow fish to the contaminated groundwater of Joint Base, Cape Cod. This site has been extensively studied by several STEEP scientists and established as a local source of PFAS to area from historical use of aqueous film-forming foam (AFFF).
Why use this specific approach? Well, by using the groundwater from the contaminated site, the research team can understand how the fish uptake PFAS when they exist as a complex mixture. More importantly, the complex mixture is representative of a realistic mixture to which other communities may be exposed downstream. Using the mobile fish lab allows for controlled experiments over time with careful monitoring.
To evaluate how mixtures of PFAS may bioconcentrate, or be taken up into the fish tissue, STEEP trainee Izak Hill and the team sampled water and fish over 21-day experiments, with samples taken at days 0, 1, 7, and 21, with kidney, liver, and gonads taken from the fish. In addition to evaluating for many regulated and known PFAS compounds, a method known as suspect screening was also applied. Suspect screening enhances the number of PFAS compounds that can be detected within the samples. Unlike traditional PFAS analysis, known as targeted analysis, suspect screening cannot as accurately determine a quantity of PFAS present.
The results of this study identified that complex mixtures could result in different patterns of bioconcentration of PFAS in fish than previously observed. For example, two regulated PFAS compounds known as perfluorohexane sulfonic acid (PFHxS) and perfluorooctane sulfonic acid (PFOS) saw a surprising result. Typically, PFOS is observed to be more bioconcentrated than PFHxS in fish, however in this mixture study, it was reversed, with PFHxS showing increased bioconcentration. Furthermore, many unregulated PFAS, known as precursors that are associated with the use of aqueous film-forming foam, were detected in the water and in the liver of some fish.
In conjunction with the recent work of former STEEP trainee Heidi Pickard, PhD, this work highlights the need for considering the uptake and exposure to a wider range of PFAS than are typically regulated or researched. The impact of mixtures must be considered in ongoing efforts to evaluate the risks of PFAS to human health, as we are highly unlikely to be exposed to only one compound at a time.
Hill NI, Becanova J, Vojta S, Barber LB, LeBlanc DR, Vajda AM, Pickard HM, Lohmann R. Bioconcentration of Per- and Polyfluoroalkyl Substances and Precursors in Fathead Minnow Tissues Environmentally Exposed to Aqueous Film-Forming Foam-Contaminated Waters. Environ Toxicol Chem. 2024 Aug;43(8):1795-1806. doi: 10.1002/etc.5926.
