PFAS in Small Mouth Bass

 Blazer, V.S., Walsh, H.L., Smith, C.R. et al. Tissue distribution and temporal and spatial assessment of per- and polyfluoroalkyl substances (PFAS) in smallmouth bass (Micropterus dolomieu) in the mid-Atlantic United States. Environ Sci Pollut Res 31, 59302–59319 (2024). https://doi.org/10.1007/s11356-024-35097-6

The article below is to a large extent excerpted from the research paper cited above and the USGS press release.

Per- and Polyfluoroalkyl Substances (PFAS) do not occur in nature, they are an entirely synthetic substance. Yet, most people in the United States have been exposed to PFAS, and have PFAS in their blood, especially perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). 

There are thousands of PFAS chemicals, and they are found in many different consumer, commercial, and industrial products. Various PFAS chemicals have been widely used for over 80 years mainly for their ability to repel oil, grease, water, and heat. PFOS and PFOA found in Scotch Guard and in Teflon and traditional Aqueous Film-Forming Foam (AFFF) - the foam used to fight aviation and other chemical fires -were the first to become widely commercially successful.

PFAS are called “forever chemicals” as they do not easily breakdown, and so build up in the environment and in tissues, apparently both human and animal. Human exposure to PFAS has been linked to health issues, such as kidney and testicular cancer, thyroid disease, liver damage, developmental toxicity, ulcerative colitis, high cholesterol, and immune dysfunction. However, much less is known about the effects of PFAS on fish health and fish populations.

Fish and other aquatic organisms can ingest PFAS from water, and diet.  In 2013, the U.S. Geological Survey, in cooperation with state natural resource agencies in Maryland, Pennsylvania, and West Virginia, began monitoring smallmouth bass (SMB, Micropterus dolomieu) in response to fish mortalities, numerous types of skin lesions, intersex, and other signs of endocrine disruption and population declines (Blazer et al. 2007, 2010, 2020; Smith et al. 2015; Walsh et al. 2018, 2022; Keplinger et al. 2022). A suite of biological indicators and monthly surface water samples for analyses of pesticides, hormones, phytoestrogens, and pharmaceuticals were monitored at four sites (two in the Potomac River, Maryland, and West Virginia and two in the Susquehanna River, Pennsylvania).

Smallmouth bass are an economically important sportfish that have experienced disease outbreaks and populations declines in numerous Chesapeake Bay watersheds. PFAS may have adverse health impacts on smallmouth bass. Therefore, the goal of this study was to evaluate the concentration of PFAS in smallmouth bass tissue samples.

Adult smallmouth Bass were collected at ten sites between 2014 and 2021 by the U.S. Geological Survey (USGS), Maryland Department of Natural Resources (MD DNR), Pennsylvania Fish and Boat Commission (PA FBC), Pennsylvania Department of Environmental Protection (PA DEP) and West Virginia Division of Natural Resources (WV DNR). 

PFAS were not part of the analyte list; however, the researchers stored and archived the  plasma from four long-term monitoring sites. Four PFAS (PFOS, PFDA, PFUnA, PFDoA) were detected in every smallmouth bass plasma sample, and concentrations of PFOS were considerably higher than the other three compounds.

The sampled sites represented some area of urban, agricultural, and forested lands in and around the Chesapeake Bay watershed. The highest total plasma concentrations of PFAS were found in smallmouth bass collected from two sites. These two sites had the highest percentage of developed land and the greatest number of EPA-identified sources of PFAS (including military installations and airports). Intermediate PFAS concentrations were found at sites with agricultural land. The lowest PFAS concentrations were found at sites with the highest percentage of forested land.

The with the lowest concentrations of PFOS and total PFAS had the largest drainage areas (3150.6 to 2207.7 sq km), the lowest developed land cover (3.2–4.5%), moderate to low agricultural land cover, and low number of PFAS facilities.

PFAS were detected in the plasma of smallmouth bass at all sites, including sites with a low percentage of developed land and sites with a low number of PFAS sources. This suggests that PFAS may be widespread in Chesapeake Bay waters and in smallmouth bass.

Developed and agricultural land may be associated with PFAS in surface water, land application of biosolids and/or the food chain.

PFAS concentrations were low in the muscle tissue of smallmouth bass, even in fish that had high plasma concentrations. The low concentration of PFAS in muscles suggests a minimal risk of human exposure to PFAS from eating smallmouth bass.

Concentrations measured in blood and other organs may be associated with health effects observed in smallmouth bass populations and require further study.