USGS PFAS study looks at which tissues the 'forever chemicals' build up in fish, plus land use & sources

Riverkeeper note: The following was written by Middle Susquehanna Riverkeeper John Zaktansky. You can contact him directly via email by clicking here.

U.S. Geological Survey (USGS) Fishery Biologist Vicki Blazer recently published an extensive study on PFAS in fish collected from nine sites, including five within the Susquehanna watershed, that show where these “forever chemicals” tend to congregate in a fish’s tissues and may shed more light on additional sources for PFAS contamination.

“PFAS tend to be higher in a fish’s blood, plasma and liver while its muscle tends to be much lower in PFAS,” said Blazer. “This, of course, is good news for people who may want to eat a fillet from the fish they catch in these waterways, but not good for the fish themselves.”

The study also looked at land use around the waterways where fish were collected as potential sources for PFAS contamination were factored into levels found in the fish.

“The highest levels of PFAS were at sites that have what would be considered major potential sources for PFAS, like military bases, airports, things like that,” Blazer said. “But some of the other sites lack some of those commonly assumed sources for PFAS but do have very high agricultural inputs. So that’s something we’re following up on, looking at those sites and factoring in possibly things like pesticides that have PFAS related to them or possible biosolids applications and what PFAS impacts biosolids can create.”

Pool of samples
In 2013, the USGS started to monitor small mouth bass in the Susquehanna River and other adjacent waterways due to an increase in species mortality, skin lesions and intersexing concerns. From 2014 through 2021, the agency collected samples from 10 different sites across multiple states to track these conditions.

“Whenever we go out and kill a fish, we take whatever we can, so we had a lot of samples and archived plasma was included with that. So when PFAS became such an issue that people were concerned about, I mentioned that we already had all these samples available, let’s have a look at them,” said Blazer. “For much of the older samples, we had mostly plasma, but we did go out to Swatara Creek and Little Neshaminy Creek with the PA Department of Environmental Protection and got fresh samples with additional tissue collection to compare levels in different parts of the fish.”

PFAS are a group of manmade compounds more commonly referred to as “forever chemicals” that all share some sort of fluorinated compound. These per- and polyfluoroalkyl substances are widely linked to serious public health and environmental impacts.

The sheer number of PFAS-related compounds can be overwhelming.

See the published study

Fig. 1 Locations and land cover surrounding smallmouth bass collection sites. Pine Creek (PC), Chillisquaque Creek (CC), West Branch Mahantango Creek (WBMC), Swatara Creek (SC), and Little Neshaminy Creek (LNC) in Pennsylvania; Cheat River (CR), South Branch Potomac River near Moorefield (SB-M), and near Petersburg (SB-P) in West Virginia; Antietam Creek (AC) in the Potomac River in Maryland; Chesapeake Bay watershed out lined in white. Credits: Homer et al. 2020; USCB, 2018, EPA; USGS, 2012; Projection USA Contiguous Albers Equal Area Conic USGS

“There are thousands of these sort of chemicals, which is one of the things that can make them so difficult to get a handle on, understand their effects and locate their sources,” Blazer said. "They’re particularly from point sources such as military bases and airports primarily because the first real public awareness of them was in firefighting foams that have been used on military bases and airports.”

Because of the strength of their chemical bond, and because they repel water so well, PFAS have been used in many other things.

“They used to be in wrappers that you’d get your Whoppers and other fast food in, although I think that has been phased out. They can be in carpeting and Teflon non-stick pan coating is another big source for people,” said Blazer.

“There are many other potential sources, and from such a wide variety of places, they get into our ground and surface water systems, and people can be exposed to them there or even through the food they eat or the air they breathe.”

Other known sources for PFAS-related compounds include stain-resistant products, paints, pesticides, certain shampoos and other personal care products, photography products, chemicals used for mining and drilling and various polishes.

According to information provided by Michael Parker of the PA Fish and Boat Commission: “PFAS are classified as emerging contaminants because their risks to the environment and human health is not completely understood yet.”

In 2018, then-Governor Wolf signed an executive order establishing the PFAS Action Team, and in 2019, PA DEP began sampling drinking water, surface water and fish tissue.

“Fish tissue sampling sites across the Commonwealth have been chosen based on evidence of high PFAS concentrations in water and in areas where angling is common,” added Parker. “There is currently only one fish consumption advisory in PA for PFOS. It is in the Neshaminy Creek watershed (Montgomery and Bucks Co.). For that entire basin, for all species, do not eat.”

Interesting findings
For the USGS study, samples were used from Pine Creek and Chillisquaque Creek in West Branch of the Susquehanna River, the Susquehanna River in Selinsgrove, West Branch Mahantango Creek and Swatara Creek off the Susquehanna’s main stem in Pennsylvania and Antietam Creek in Maryland. It also includes Little Neshaminy Creek in the Delaware River system in Southeast Pennsylvania and three sites from the Potomac River basin: Cheat River, South Branch Potomac-Moorefield and South Branch Potomac-Petersburg (all in West Virginia).

“There are other papers out there that support higher concentrations of PFAS in a fish’s blood or plasma vs. the muscle, but many of those look at one species compared to another. What was interesting to me here in our study,” said Blazer,” is that at Little Neshaminy and Swatara creeks, in the same species, we saw different tissue distribution. At Little Neshaminy, for example, we saw more total PFAS in their liver than in the blood or plasma. Does that mean they were getting more through their diet?”

The other interesting concept for Blazer at this site was comparing blood PFAS levels to plasma PFAS levels.

“Most studies have shown PFAS higher in plasma vs. whole blood, but there again at Little Neshaminy, it was higher in the whole blood, meaning at first, to me at least, it is accumulating specifically in the blood cells. Is it because in the plasma it is specifically tied to plasma proteins?” Blazer pondered. “There are just a lot of questions left to be answered, but to me, this is just one of many interesting takeaways from this study.”
 
Land use aspects of each waterway and the associated PFAS found in fish collected at those corresponding sites was also studied.

Little Neshaminy Creek was by far the most developed waterway (70.7 percent) compared to Antietam Creek (17.3) and Swatara Creek (13.9) next on the list. Those three also ranked the highest among the waterways in total PFAS facilities in their watersheds (60, 25 and 39, respectively).

Not surprisingly, Little Neshaminy Creek easily led the other waterways in total PFAS detected in the fish sampled. Antietam and Swatara Creek were second and third.

However, the next three highest total PFAS rates by a noticeable margin fairly equally spread across the Susquehanna-Selingrove site, Chillisquaque Creek and West Branch of the Mahantango Creek.

“These would be areas with higher agricultural and pesticide usage,” said Blazer. “There may not be as much infrastructure in these spots directly related typically with PFAS contamination, but it does lead us to want to take next steps looking specifically at pesticides that are known to contain PFAS that may be used in these areas or other potential sources.”

Another interesting outlier is the Pine Creek site, which tested as one of the lowest in terms of total PFAS in fish samples despite having one of the highest total PFAS facilities (23) on the list.

“We chose that site, which is our farthest north, to represent a mostly forested area back when we started the endocrine disruptor study,” Blazer said. “While Pine Creek does have a lot of facilities listed, a number of them are inactive unconventional gas and oil pads and things like that, so a little hard to tease out and not really sure what that means.”

Tissue concentration: Swatara Creek

Fig. 5 Tissue concentrations (mean in ng/g with standard error bars) in 17 smallmouth bass collected from Swatara Creek (SC), Pennsylvania. A Total PFAS; B PFOS; C PFUnA; D PFDA

​Tissue concentration: L. Neshaminy 

Fig. 6 Tissue distribution of specific PFAS compounds (in ng/g mean with standard error bars) detected in 11 smallmouth bass from Little Neshaminy Creek (LNC), Pennsylvania. A Total PFAS. B PFOS. C PFUnA. D PFDA

Land use by site

Table 2 Land use characteristics of the upstream watershed of the sites for spatial comparison

Total PFAS by site

Fig. 2 Spatial distribution of PFAS in smallmouth bass plasma. A Total PFAS, B PFOS, C PFDoA, D PFUnA, and E PFDA, at sites in the Cheat River (CR); South Branch Petersburg (SB-P), South Branch Moorefield (SB-M), and Antietam Creek (AC) in the Potomac River; Susquehanna River Selinsgrove (SS), Pine (PC), West Branch Mahantango Creek (WBMC), Chillisquaque Creek (CC), and Swatara Creek (SC) in the Susquehanna River; and Little Neshaminy Creek (LNC) in the Delaware River. Numbers indicate the sample size of each site

Blazer took time in the study to look at differences in PFAS based on fish gender.

“We didn’t see big differences in PFAS testing between gonads and ovaries, which kind of surprised me, Blazer said. “However, males still tended to have higher rates of at least three of the four PFAS compounds we tested for.”

What's next 
Blazer and her team are developing next steps around the potential biological effects of PFAS on the fish.

“We want to know if there are specific PFAS that have an adverse effect on the fish. Also, now that we have a baseline for what fish are experiencing regularly in their plasma as far as PFAS levels in the environment, we can replicate that in the lab and study it better,” she said. “For example, at our Columbia, Missouri, lab we are exposing young just-hatched smallmouth bass and collecting them at seven and 90-days exposure and looking a whole lot of end points.”

Blazer added that there is another study being done where smallmouth bass immune cells are being exposed to PFAS levels similar to what they’ve found in these bass “and seeing what sort of impact it has on disease resistance and immune response.”

And Blazer continues to advocate work toward better understanding how PFAS interact with a wide variety of other contaminants that fish and other species experience collaboratively.

“So from many of the same fish we have PFAS compound data, we also have mercury actually in the fish, and we have water concentrations of wastewater and pesticides and so much more. What we are trying to find is a statistician to help us – how do you factor in all those chemicals and different exposures,” Blazer asked. “The PFAS are accumulating in some organs. The mercury in other organs, and so on. How do you put that all together? We’re still wrestling with that.”

The key, for now, is to continue asking questions, gathering data and sharing the results with as many people as possible, she said.

“The more people know about this and how it impacts different levels of our ecosystem, the more they’ll be willing to get involved and hopefully make things better moving forward.”

Check out the full published study by Blazer and the USGS online here or download the PDF here.

One way to check out more data from this and other USGS-related studies on the Susquehanna River and other places is to check out the agency's data release page.