Small Fish, Big Problem: Bioaccumulation in Iowa's Waterways

As the sunlight shimmered across the surface of the water and the wind jostled my 6-year-old hair, I felt a tug on my fishing line. Excitedly, I yanked my hands above my head! The fish recoiled and began to pull away with strength rivalling my own. As the reel repeatedly wound and my line moved closer and closer, the fish finally emerged from the water. There it was — dangling in the sunlight, a 2-inch bluegill. My dad chuckled beside me, helped me get the fish from my line, and returned the fish to the water. “NO!” I yelled, “We could have eaten that!” My dad laughed, knowing what I did not: “That fish has just started its life. Let it be food for another fish. We want to catch bigger fish.” Little did I know that in that moment, my dad taught me about a foundational principle driving one of Iowa’s water quality issues 25 years later. 

Microplastics, per- and polyfluoroalkyl substances (better known as PFAS), antibiotic resistance genes, pharmaceuticals and personal care products, and pesticides are all contaminants of global concern. Many of these contaminants can be found within Iowa waterways, rural, urban, large, and small. Microplastics and PFAS have been described as “forever chemicals” because they resist breaking down, and they move readily through soil, water, and living organisms. Surface water runoff is one of the most common ways that these chemicals can move throughout the environment, leading to increased levels of forever chemicals in both urban and rural water pathways. A recent study by University of Iowa researchers (Meppelink et al., 2025) found that both microplastics and PFAS were found throughout the water, sediment, and fish of small, agricultural waterways in Iowa. Indeed, fish had the highest concentration of PFAS when compared to the water and stream bed sediment. Because fish cannot break these chemicals down, PFAS and microplastics buildup over time — the older the fish, the higher the concentration. This process is known as bioaccumulation. 

“Let it be food for another fish,” my dad said to me — and as it turns out, that is exactly the problem. As PFAS and microplastics accumulate in these smaller fish as they age, they can be eaten by predators (e.g., largemouth bass). If a largemouth bass eats one of these smaller fish, where do the PFAS and microplastics go? If the smaller fish are unable to break down these chemicals, the larger fish cannot either.  

Biomagnification is the process where forever chemicals in smaller fish end up making their way up the food chain, leading to increased concentrations at the top of the food web. As a largemouth bass eats a guppy, the PFAS found within these smaller fish accumulate due to the persistence of the forever chemicals. Since humans sit at the top of the food web, our bodies accumulate what could not break down in the links before us. 

For many Iowans, fishing is not just a hobby; it’s dinner. When humans consume forever chemicals, they increase their risk for increased cholesterol levels, lower birthweights, decreased antibody responses to vaccines in children, various cancers (e.g., kidney, testicular, prostate, ovarian, non-Hodgkin lymphoma), pregnancy-induced hypertension or preeclampsia, changes in liver enzymes, as well as other health effects (ATSDR, November 2024; IEC, 2025). IEC’s recent “Environmental Risk Factors and Iowa’s Cancer Crisis” report includes more information about specific cancers associated with PFAS exposure.  

The next time you cast a line into an Iowa lake or river, I hope you feel that same excitement I felt as a 6-year-old. Fishing connects us to this land and to each other in ways that matter. But understanding what is in our water, and in our fish, is part of that connection too. Iowa's waterways deserve the same care and attention we give to the traditions they make possible. 

Kean Roberts is the Water Program Associate for the Iowa Environmental Council. 

Citations: 

Agency for Toxic Substances and Disease Registry. “Health Effects: PFAS Information for Clinicians – 2024." ATSDR, https://www.atsdr.cdc.gov/pfas/hcp/clinical-overview/health-effects.html. Accessed June 11, 2026. 

Butzlaff, A. H., Deighton, J., Le, T., Brougham, A., Bessler, S. M., McKnight, T., & Ateia, M. (2025). PFAS, 6-PPD-Q, and microplastics in urban sewer overflows: co-occurrence and high-rate treatment assessment. Emerging Contaminants, 1(1), 5. 

Ghosh, D., Ghosh, A., & Bhadury, P. (2022). Arsenic through aquatic trophic levels: effects, transformations and biomagnification—a concise review. Geoscience Letters, 9(1), 20. 

Iowa Environmental Council. (2026) Environmental Risk Factors and Iowa’s Cancer Crisis.  

Meppelink, S. M., Kolpin, D. W., LeFevre, G. H., Cwiertny, D. M., Givens, C. E., Green, L. A.,  Hubbard, L. E., Iwanowicz, L. R., Lane, R. F., Mianecki, A. L., O’Shea, P. S., Raines, C. D., Scott, J. W., Thompson, D. A., Wilson, M. C., & Gray, J. L. (2025). Assessing microplastics, per-and polyfluoroalkyl substances (PFAS), and other contaminants of global concern in wadable agricultural streams in Iowa. Environmental Science: Processes & Impacts, 27(5), 1401-1422. 

Phillip, A. (2025). Understanding per-and polyfluoroalkyl substances (PFAS): Environmental persistence, health risks, and regulatory challenges. European Journal of Scientific Research and Reviews, 2(4), 199-211.