What goes around, comes around: Accumulation of PFAS in Marine Critters

­­­­­­­­­­­Source Article: Langberg, H. A., Breedveld, G. D., Grønning, H. M., Kvennås, M., Jenssen, B. M., & Hale, S. E. Bioaccumulation of fluorotelomer sulfonates and perfluoroalkyl acids in marine organisms living in aqueous film forming foam (AFFF) impacted waters. Environ. Sci. Technol. 2019.  DOI: 10.1021/acs.est.9b00927

Cover Photo: Green shore crabs have been shown to accumulate PFAS near an air base in Norway. Source.

What are PFAS?

“PFAS” stands for per- and polyfluorinated alkyl substances… quite a mouthful! PFAS have been getting a lot of attention lately because they are being detected all over the place—including in food, remote mountain streams, and many humans. But, what are they?

PFAS are man-made chemicals that have been produced since the 1940s for uses in industry, manufacturing, and consumer products. They are particularly useful in making non-stick and stain-resistant products (think cookware, clothing, and carpets) and are very good flame-retardants. They are also part of a family of chemicals that are an emerging concern to human health and the environment. Even though they come in thousands of different forms, they all contain carbon and fluorine bonds, which are very hard to break, making PFAS extremely persistent in the environment.

In other words, once they get around, they stay around.

The major historical players, or “legacy” PFAS, are Perfluorooctanesulfonic acid (PFOS) and Perfluorooctanoic acid (PFOA). These legacy compounds are the most studied types of PFAS, and high levels of exposure have been shown to cause health problems, including liver and kidney damage, in laboratory animals. They’ve also been associated with adverse health effects in humans. Production of these specific molecules has largely ended in the US due to voluntary phase-outs by the chemical industry. However, their persistence means that these legacy compounds are still present in the environment. Plus, they can still be manufactured in other countries.

The important role left empty when industry ceased production of PFOA and PFOS has been filled by a slew of other PFAS, including one called GenX. These new PFAS molecules are not as well-studied and their health effects are not well known, so discovering and evaluating these compounds in the environment is an important area of ongoing research. You can read more about PFAS here.

 

Figure 1. AFFF is being used to put out a fire during training at an air force base in Florida. Source
Where are PFAS coming from?

PFAS can be found at low levels in many consumer products, especially those with non-stick and stain-resistant properties. However, high-level environmental exposure to PFAS largely comes from chemical and industrial manufacturing plants and sites where regular firefighting occurs (such as refineries and military facilities). The latter source is due to the frequent use of aqueous film-forming foams (AFFFs), which often contain PFAS, in firefighting. When putting out fires, large amounts of these foams are dispensed onto the ground (at the fire), which can then enter the environment through water runoff and leaching into the ground.

Where are they going?

In a recent study, a Norwegian research team led by Håkon Langberg sought to determine where PFAS went after entering the environment. They were particularly interested in how uptake and bioaccumulation (or the buildup of chemicals within an organism over time) differs between species. They collected samples from several types of marine organisms, storm water, and the abiotic environment (fjord water and sediments) in a fjord surrounding a military airbase in the Norwegian Arctic that was known to have used AFFF. Their sampling sites, shown in Figure 2, were located close to storm-water runoff discharge points from the air station (A, C, D, G, and H), fire station (B), and firefighting training area (E and F) on the base. They also collected samples from a reference station several miles from the base, believed not to be near a PFAS source.

Figure 2. PFAS accumulation varies with species and location. Sites (letters) where samples were collected surrounding an air base in Norway. Bar graphs indicate relative levels of PFAS detected in marine organisms at each sampling site. Reprinted with permission from Langberg et al. Copyright 2019 American Chemical Society.

The research team found that concentrations of PFAS in the storm-water were highest coming from the firefighting training facility, where the use of AFFF was also the highest. Interestingly, PFOS was the most prevalent type of PFAS they detected, despite being phased out of AFFF in Norway in 2007. This illustrates how long these contaminants will stick around in the environment. The rough waters in the fjord effectively mix up and dilute contaminants, so the concentration of PFAS in the fjord water and sediments was below what they could accurately measure. However, PFAS was still found to build up in the bodies of marine critters.

They compared PFAS concentrations in fish and invertebrates (marine snails and crabs), which represented mobile and less-mobile organisms, respectively. Fish swim around substantially over their lifetime, ingesting water and food from all over the fjord. However, snails and crabs don’t travel very far afield, so they will likely only be exposed to the environment near the storm-water sources their whole lives (or, at least, a larger portion of it).

It turns out this mobility factor makes a big difference! The researchers found that concentrations of PFAS in fish were similar at all sampling sights around the air station, while PFAS in invertebrates reflected the relative level of PFAS in the storm-water sources. The level of accumulation of several types PFAS also differed between fish and invertebrates, indicating fish break down and eliminate some PFAS much faster than crabs and snails.

 

Figure 3. Accumulation of PFAS in marine organisms is controlled by the organisms rates of uptake and elimination of these chemicals. Sometimes they can enter as one type of PFAS and exit as others, due to enzymatic degradation (or breakdown) within the organism. Reprinted with permission from Langberg et al. Copyright 2019 American Chemical Society.
What does this mean moving forward?

Langberg’s team provided one of the first comparisons between PFAS accumulation in fish and invertebrates. Their results indicated that there is a difference in how PFAS behave in these organisms, specifically in the organisms’ uptake and elimination of these compounds. The researchers also demonstrated that invertebrates provide a better location-specific indication of the accumulation of PFAS than fish. Furthermore, bioaccumulation patterns differ between organisms, so risk assessments should include a diverse set of organisms. Not only can PFAS bioaccumulate (become concentrated) in individual organisms, they can also biomagnify up the food chain (increasing in concentration as organisms containing the compound are ingested by predators – think Bald Eagles and DDT). As humans, with a position at the top of many food chains, understanding how PFAS accumulates in different organisms has significant implications for our health. By comparing fish and crabs, this study gives us a better picture of what could be in our sea food.

 

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Mary Davis

I earned my PhD in Chemical Engineering from Princeton University in 2018, where my research focused on nanoscale polymer systems and how their properties change with geometry. I am now applying my background in polymers to environmental systems as a postdoctoral research associate at the U.S. EPA. This involves studying the breakdown of plastics and the generation of microplastics in the environment, as well as their interactions with other pollutants. When I’m not working in the lab, I enjoy crafting, cooking, and being outside.

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